The Objective Caml system
release 3.01
Documentation and user's manual
Xavier Leroy
(with Damien Doligez, Jacques Garrigue, Didier Rémy and Jérôme Vouillon)
March 8, 2001
Copyright © 2000 Institut National de Recherche en Informatique et en
Automatique
---------------------------------------------------------------
This manual is also available in PDF (1). Postscript (2), DVI
(3), as a bundle of HTML files (4), and as a bundle of Emacs
Info files (5).
---------------------------------------------------------------
---------------------------------------
(1) ftp://ftp.inria.fr/lang/caml-light/ocaml-3.01-refman.pdf
(2) ftp://ftp.inria.fr/lang/caml-light/ocaml-3.01-refman.ps.gz
(3) ftp://ftp.inria.fr/lang/caml-light/ocaml-3.01-refman.dvi.gz
(4) ftp://ftp.inria.fr/lang/caml-light/ocaml-3.01-refman.html.tar.gz
(5) ftp://ftp.inria.fr/lang/caml-light/ocaml-3.01-refman.info.tar.gz
Foreword
********
This manual documents the release 3.01 of the Objective Caml system. It is
organized as follows.
- Part I, ``An introduction to Objective Caml'', gives an overview of the
language.
- Part II, ``The Objective Caml language'', is the reference description of
the language.
- Part III, ``The Objective Caml tools'', documents the compilers, toplevel
system, and programming utilities.
- Part IV, ``The Objective Caml library'', describes the modules provided in
the standard library.
Conventions
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Objective Caml runs on several operating systems. The parts of this manual
that are specific to one operating system are presented as shown below:
MacOS:
This is material specific to MacOS 7, 8, 9. (For MacOS X, see
``Unix''.)
Unix:
This is material specific to the Unix family of operating
systems, including Linux and MacOS X.
Windows:
This is material specific to Microsoft Windows (95, 98, ME, NT,
2000).
License
*=*=*=*
The Objective Caml system is copyright © 1996, 1997, 1998, 1999, 2000, 2001
Institut National de Recherche en Informatique et en Automatique (INRIA). INRIA
holds all ownership rights to the Objective Caml system.
The Objective Caml system is open source and can be freely redistributed. See
the file LICENSE in the distribution for licensing information. The present
documentation is distributed under the same conditions.
Availability
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The complete Objective Caml distribution can be accessed via the Caml Web
site (6), or directly on the anonymous FTP archive (7). The Caml Web site (8)
contains a lot of additional information on the Caml family of languages.
---------------------------------------
(6) http://caml.inria.fr/
(7) ftp://ftp.inria.fr/lang/caml-light/
(8) http://caml.inria.fr/
Part: I
*******
An introduction to Objective Caml
**********************************
Chapter 1 The core language
*******************************
This part of the manual is a tutorial introduction to the Objective Caml
language. A good familiarity with programming in a conventional languages (say,
Pascal or C) is assumed, but no prior exposure to functional languages is
required. The present chapter introduces the core language. Chapter 3 deals
with the object-oriented features, and chapter 4 with the module system.
1.1 Basics
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For this overview of Caml, we use the interactive system, which is started by
running ocaml from the Unix shell, or by launching the OCamlwin.exe application
under Windows. This tutorial is presented as the transcript of a session with
the interactive system: lines starting with # represent user input; the system
responses are printed below, without a leading #.
Under the interactive system, the user types Caml phrases, terminated by ;;,
in response to the # prompt, and the system compiles them on the fly, executes
them, and prints the outcome of evaluation. Phrases are either simple
expressions, or let definitions of identifiers (either values or functions).
<<#1+2*3;;
- : int = 7
#let pi = 4.0 *. atan 1.0;;
val pi : float = 3.14159265359
#let square x = x *. x;;
val square : float -> float = <fun>
#square(sin pi) +. square(cos pi);;
- : float = 1
>>
The Caml system computes both the value and the type for each phrase. Even
function parameters need no explicit type declaration: the system infers their
types from their usage in the function. Notice also that integers and
floating-point numbers are distinct types, with distinct operators: + and *
operate on integers, but +. and *. operate on floats.
<<#1.0 * 2;;
This expression has type float but is here used with type int
>>
Recursive functions are defined with the let rec binding:
<<#let rec fib n =
# if n < 2 then 1 else fib(n-1) + fib(n-2);;
val fib : int -> int = <fun>
#fib 10;;
- : int = 89
>>
1.2 Data types
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In addition to integers and floating-point numbers, Caml offers the usual
basic data types: booleans, characters, and character strings.
<<#(1 < 2) = false;;
- : bool = false
#'a';;
- : char = 'a'
#"Hello world";;
- : string = "Hello world"
>>
Predefined data structures include tuples, arrays, and lists. General
mechanisms for defining your own data structures are also provided. They will
be covered in more details later; for now, we concentrate on lists. Lists are
either given in extension as a bracketed list of semicolon-separated elements,
or built from the empty list [] (pronounce ``nil'') by adding elements in front
using the :: (``cons'') operator.
<<#let l = ["is"; "a"; "tale"; "told"; "etc."];;
val l : string list = ["is"; "a"; "tale"; "told"; "etc."]
#"Life" :: l;;
- : string list = ["Life"; "is"; "a"; "tale"; "told"; "etc."]
>>
As with all other Caml data structures, lists do not need to be explicitly
allocated and deallocated from memory: all memory management is entirely
automatic in Caml. Similarly, there is no explicit handling of pointers: the
Caml compiler silently introduces pointers where necessary.
As with most Caml data structures, inspecting and destructuring lists is
performed by pattern-matching. List patterns have the exact same shape as list
expressions, with identifier representing unspecified parts of the list. As an
example, here is insertion sort on a list:
<<#let rec sort lst =
# match lst with
# [] -> []
# | head :: tail -> insert head (sort tail)
#and insert elt lst =
# match lst with
# [] -> [elt]
# | head :: tail -> if elt <= head then elt :: lst else head :: insert elt
tail
#;;
val sort : 'a list -> 'a list = <fun>
val insert : 'a -> 'a list -> 'a list = <fun>
#sort l;;
- : string list = ["a"; "etc."; "is"; "tale"; "told"]
>>
The type inferred for sort, 'a list -> 'a list, means that sort can actually
apply to lists of any type, and returns a list of the same type. The type 'a is
a type variable, and stands for any given type. The reason why sort can apply
to lists of any type is that the comparisons (=, <=, etc.) are polymorphic in
Caml: they operate between any two values of the same type. This makes sort
itself polymorphic over all list types.
<<#sort [6;2;5;3];;
- : int list = [2; 3; 5; 6]
#sort [3.14; 2.718];;
- : float list = [2.718; 3.14]
>>
The sort function above does not modify its input list: it builds and returns
a new list containing the same elements as the input list, in ascending order.
There is actually no way in Caml to modify in-place a list once it is built: we
say that lists are immutable data structures. Most Caml data structures are
immutable, but a few (most notably arrays) are mutable, meaning that they can
be modified in-place at any time.
1.3 Functions as values
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Caml is a functional language: functions in the full mathematical sense are
supported and can be passed around freely just as any other piece of data. For
instance, here is a deriv function that takes any float function as argument
and returns an approximation of its derivative function:
<<#let deriv f dx = function x -> (f(x +. dx) -. f(x)) /. dx;;
val deriv : (float -> float) -> float -> float -> float = <fun>
#let sin' = deriv sin 1e-6;;
val sin' : float -> float = <fun>
#sin' pi;;
- : float = -1.00000000014
>>
Even function composition is definable:
<<#let compose f g = function x -> f(g(x));;
val compose : ('a -> 'b) -> ('c -> 'a) -> 'c -> 'b = <fun>
#let cos2 = compose square cos;;
val cos2 : float -> float = <fun>
>>
Functions that take other functions as arguments are called ``functionals'',
or ``higher-order functions''. Functionals are especially useful to provide
iterators or similar generic operations over a data structure. For instance,
the standard Caml library provides a List.map functional that applies a given
function to each element of a list, and returns the list of the results:
<<#List.map (function n -> n * 2 + 1) [0;1;2;3;4];;
- : int list = [1; 3; 5; 7; 9]
>>
This functional, along with a number of other list and array functionals, is
predefined because it is often useful, but there is nothing magic with it: it
can easily be defined as follows.
<<#let rec map f l =
# match l with
# [] -> []
# | hd :: tl -> f hd :: map f tl;;
val map : ('a -> 'b) -> 'a list -> 'b list = <fun>
>>
1.4 Records and variants
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User-defined data structures include records and variants. Both are defined
with the type declaration. Here, we declare a record type to represent rational
numbers.
<<#type ratio = {num: int; denum: int};;
type ratio = { num : int; denum : int; }
#let add_ratio r1 r2 =
# {num = r1.num * r2.denum + r2.num * r1.denum;
# denum = r1.denum * r2.denum};;
val add_ratio : ratio -> ratio -> ratio = <fun>
#add_ratio {num=1; denum=3} {num=2; denum=5};;
- : ratio = {num=11; denum=15}
>>
The declaration of a variant type lists all possible shapes for values of
that type. Each case is identified by a name, called a constructor, which
serves both for constructing values of the variant type and inspecting them by
pattern-matching. Constructor names are capitalized to distinguish them from
variable names (which must start with a lowercase letter). For instance, here
is a variant type for doing mixed arithmetic (integers and floats):
<<#type number = Int of int | Float of float | Error;;
type number = Int of int | Float of float | Error
>>
This declaration expresses that a value of type number is either an integer,
a floating-point number, or the constant Error representing the result of an
invalid operation (e.g. a division by zero).
Enumerated types are a special case of variant types, where all alternatives
are constants:
<<#type sign = Positive | Negative;;
type sign = Positive | Negative
#let sign_int n = if n >= 0 then Positive else Negative;;
val sign_int : int -> sign = <fun>
>>
To define arithmetic operations for the number type, we use pattern-matching
on the two numbers involved:
<<#let add_num n1 n2 =
# match (n1, n2) with
# (Int i1, Int i2) ->
# (* Check for overflow of integer addition *)
# if sign_int i1 = sign_int i2 && sign_int(i1 + i2) <> sign_int i1
# then Float(float i1 +. float i2)
# else Int(i1 + i2)
# | (Int i1, Float f2) -> Float(float i1 +. f2)
# | (Float f1, Int i2) -> Float(f1 +. float i2)
# | (Float f1, Float f2) -> Float(f1 +. f2)
# | (Error, _) -> Error
# | (_, Error) -> Error;;
val add_num : number -> number -> number = <fun>
#add_num (Int 123) (Float 3.14159);;
- : number = Float 126.14159
>>
The most common usage of variant types is to describe recursive data
structures. Consider for example the type of binary trees:
<<#type 'a btree = Empty | Node of 'a * 'a btree * 'a btree;;
type 'a btree = Empty | Node of 'a * 'a btree * 'a btree
>>
This definition reads as follow: a binary tree containing values of type 'a
(an arbitrary type) is either empty, or is a node containing one value of type
'a and two subtrees containing also values of type 'a, that is, two 'a btree.
Operations on binary trees are naturally expressed as recursive functions
following the same structure as the type definition itself. For instance, here
are functions performing lookup and insertion in ordered binary trees (elements
increase from left to right):
<<#let rec member x btree =
# match btree with
# Empty -> false
# | Node(y, left, right) ->
# if x = y then true else
# if x < y then member x left else member x right;;
val member : 'a -> 'a btree -> bool = <fun>
#let rec insert x btree =
# match btree with
# Empty -> Node(x, Empty, Empty)
# | Node(y, left, right) ->
# if x <= y then Node(y, insert x left, right)
# else Node(y, left, insert x right);;
val insert : 'a -> 'a btree -> 'a btree = <fun>
>>
1.5 Imperative features
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Though all examples so far were written in purely applicative style, Caml is
also equipped with full imperative features. This includes the usual while and
for loops, as well as mutable data structures such as arrays. Arrays are either
given in extension between [| and |] brackets, or allocated and initialized
with the Array.create function, then filled up later by assignments. For
instance, the function below sums two vectors (represented as float arrays)
componentwise.
<<#let add_vect v1 v2 =
# let len = min (Array.length v1) (Array.length v2) in
# let res = Array.create len 0.0 in
# for i = 0 to len - 1 do
# res.(i) <- v1.(i) +. v2.(i)
# done;
# res;;
val add_vect : float array -> float array -> float array = <fun>
#add_vect [| 1.0; 2.0 |] [| 3.0; 4.0 |];;
- : float array = [|4; 6|]
>>
Record fields can also be modified by assignment, provided they are declared
mutable in the definition of the record type:
<<#type mutable_point = { mutable x: float; mutable y: float };;
type mutable_point = { mutable x : float; mutable y : float; }
#let translate p dx dy =
# p.x <- p.x +. dx; p.y <- p.y +. dy;;
val translate : mutable_point -> float -> float -> unit = <fun>
#let mypoint = { x = 0.0; y = 0.0 };;
val mypoint : mutable_point = {x=0; y=0}
#translate mypoint 1.0 2.0;;
- : unit = ()
#mypoint;;
- : mutable_point = {x=1; y=2}
>>
Caml has no built-in notion of variable -- identifiers whose current value
can be changed by assignment. (The let binding is not an assignment, it
introduces a new identifier with a new scope.) However, the standard library
provides references, which are mutable indirection cells (or one-element
arrays), with operators ! to fetch the current contents of the reference and :=
to assign the contents. Variables can then be emulated by let-binding a
reference. For instance, here is an in-place insertion sort over arrays:
<<#let insertion_sort a =
# for i = 1 to Array.length a - 1 do
# let val_i = a.(i) in
# let j = ref i in
# while !j > 0 && val_i < a.(!j - 1) do
# a.(!j) <- a.(!j - 1);
# j := !j - 1
# done;
# a.(!j) <- val_i
# done;;
val insertion_sort : 'a array -> unit = <fun>
>>
References are also useful to write functions that maintain a current state
between two calls to the function. For instance, the following pseudo-random
number generator keeps the last returned number in a reference:
<<#let current_rand = ref 0;;
val current_rand : int ref = {contents=0}
#let random () =
# current_rand := !current_rand * 25713 + 1345;
# !current_rand;;
val random : unit -> int = <fun>
>>
Again, there is nothing magic with references: they are implemented as a
one-field mutable record, as follows.
<<#type 'a ref = { mutable contents: 'a };;
type 'a ref = { mutable contents : 'a; }
#let (!) r = r.contents;;
val ( ! ) : 'a ref -> 'a = <fun>
#let (:=) r newval = r.contents <- newval;;
val ( := ) : 'a ref -> 'a -> unit = <fun>
>>
1.6 Exceptions
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Caml provides exceptions for signalling and handling exceptional conditions.
Exceptions can also be used as a general-purpose non-local control structure.
Exceptions are declared with the exception construct, and signalled with the
raise operator. For instance, the function below for taking the head of a list
uses an exception to signal the case where an empty list is given.
<<#exception Empty_list;;
exception Empty_list
#let head l =
# match l with
# [] -> raise Empty_list
# | hd :: tl -> hd;;
val head : 'a list -> 'a = <fun>
#head [1;2];;
- : int = 1
#head [];;
Uncaught exception: Empty_list.
>>
Exceptions are used throughout the standard library to signal cases where the
library functions cannot complete normally. For instance, the List.assoc
function, which returns the data associated with a given key in a list of (key,
data) pairs, raises the predefined exception Not_found when the key does not
appear in the list:
<<#List.assoc 1 [(0, "zero"); (1, "one")];;
- : string = "one"
#List.assoc 2 [(0, "zero"); (1, "one")];;
Uncaught exception: Not_found.
>>
Exceptions can be trapped with the try...with construct:
<<#let name_of_binary_digit digit =
# try
# List.assoc digit [0, "zero"; 1, "one"]
# with Not_found ->
# "not a binary digit";;
val name_of_binary_digit : int -> string = <fun>
#name_of_binary_digit 0;;
- : string = "zero"
#name_of_binary_digit (-1);;
- : string = "not a binary digit"
>>
The with part is actually a regular pattern-matching on the exception value.
Thus, several exceptions can be caught by one try...with construct. Also,
finalization can be performed by trapping all exceptions, performing the
finalization, then raising again the exception:
<<#let temporarily_set_reference ref newval funct =
# let oldval = !ref in
# try
# ref := newval;
# let res = funct () in
# ref := oldval;
# res
# with x ->
# ref := oldval;
# raise x;;
val temporarily_set_reference : 'a ref -> 'a -> (unit -> 'b) -> 'b = <fun>
>>
1.7 Symbolic processing of expressions
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We finish this introduction with a more complete example representative of
the use of Caml for symbolic processing: formal manipulations of arithmetic
expressions containing variables. The following variant type describes the
expressions we shall manipulate:
<<#type expression =
# Const of float
# | Var of string
# | Sum of expression * expression (* e1 + e2 *)
# | Diff of expression * expression (* e1 - e2 *)
# | Prod of expression * expression (* e1 * e2 *)
# | Quot of expression * expression (* e1 / e2 *)
#;;
type expression =
Const of float
| Var of string
| Sum of expression * expression
| Diff of expression * expression
| Prod of expression * expression
| Quot of expression * expression
>>
We first define a function to evaluate an expression given an environment
that maps variable names to their values. For simplicity, the environment is
represented as an association list.
<<#exception Unbound_variable of string;;
exception Unbound_variable of string
#let rec eval env exp =
# match exp with
# Const c -> c
# | Var v ->
# (try List.assoc v env with Not_found -> raise(Unbound_variable v))
# | Sum(f, g) -> eval env f +. eval env g
# | Diff(f, g) -> eval env f -. eval env g
# | Prod(f, g) -> eval env f *. eval env g
# | Quot(f, g) -> eval env f /. eval env g;;
val eval : (string * float) list -> expression -> float = <fun>
#eval [("x", 1.0); ("y", 3.14)] (Prod(Sum(Var "x", Const 2.0), Var "y"));;
- : float = 9.42
>>
Now for a real symbolic processing, we define the derivative of an expression
with respect to a variable dv:
<<#let rec deriv exp dv =
# match exp with
# Const c -> Const 0.0
# | Var v -> if v = dv then Const 1.0 else Const 0.0
# | Sum(f, g) -> Sum(deriv f dv, deriv g dv)
# | Diff(f, g) -> Diff(deriv f dv, deriv g dv)
# | Prod(f, g) -> Sum(Prod(f, deriv g dv), Prod(deriv f dv, g))
# | Quot(f, g) -> Quot(Diff(Prod(deriv f dv, g), Prod(f, deriv g dv)),
# Prod(g, g))
#;;
val deriv : expression -> string -> expression = <fun>
#deriv (Quot(Const 1.0, Var "x")) "x";;
- : expression =
Quot
(Diff (Prod (Const 0, Var "x"), Prod (Const 1, Const 1)),
Prod (Var "x", Var "x"))
>>
1.8 Pretty-printing and parsing
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As shown in the examples above, the internal representation (also called
abstract syntax) of expressions quickly becomes hard to read and write as the
expressions get larger. We need a printer and a parser to go back and forth
between the abstract syntax and the concrete syntax, which in the case of
expressions is the familiar algebraic notation (e.g. 2*x+1).
For the printing function, we take into account the usual precedence rules
(i.e. * binds tighter than +) to avoid printing unnecessary parentheses. To
this end, we maintain the current operator precedence and print parentheses
around an operator only if its precedence is less than the current precedence.
<<#let print_expr exp =
# (* Local function definitions *)
# let open_paren prec op_prec =
# if prec > op_prec then print_string "(" in
# let close_paren prec op_prec =
# if prec > op_prec then print_string ")" in
# let rec print prec exp = (* prec is the current precedence *)
# match exp with
# Const c -> print_float c
# | Var v -> print_string v
# | Sum(f, g) ->
# open_paren prec 0;
# print 0 f; print_string " + "; print 0 g;
# close_paren prec 0
# | Diff(f, g) ->
# open_paren prec 0;
# print 0 f; print_string " - "; print 1 g;
# close_paren prec 0
# | Prod(f, g) ->
# open_paren prec 2;
# print 2 f; print_string " * "; print 2 g;
# close_paren prec 2
# | Quot(f, g) ->
# open_paren prec 2;
# print 2 f; print_string " / "; print 3 g;
# close_paren prec 2
# in print 0 exp;;
val print_expr : expression -> unit = <fun>
#let e = Sum(Prod(Const 2.0, Var "x"), Const 1.0);;
val e : expression = Sum (Prod (Const 2, Var "x"), Const 1)
#print_expr e; print_newline();;
2 * x + 1
- : unit = ()
#print_expr (deriv e "x"); print_newline();;
2 * 1 + 0 * x + 0
- : unit = ()
>>
Parsing (transforming concrete syntax into abstract syntax) is usually more
delicate. Caml offers several tools to help write parsers: on the one hand,
Caml versions of the lexer generator Lex and the parser generator Yacc (see
chapter 12), which handle LALR(1) languages using push-down automata; on the
other hand, a predefined type of streams (of characters or tokens) and
pattern-matching over streams, which facilitate the writing of
recursive-descent parsers for LL(1) languages. An example using ocamllex and
ocamlyacc is given in chapter 12. Here, we will use stream parsers.
<<#open Genlex;;
#let lexer = make_lexer ["("; ")"; "+"; "-"; "*"; "/"];;
val lexer : char Stream.t -> Genlex.token Stream.t = <fun>
>>
For the lexical analysis phase (transformation of the input text into a
stream of tokens), we use a ``generic'' lexer provided in the standard library
module Genlex. The make_lexer function takes a list of keywords and returns a
lexing function that ``tokenizes'' an input stream of characters. Tokens are
either identifiers, keywords, or literals (integer, floats, characters,
strings). Whitespace and comments are skipped.
<<#let token_stream = lexer(Stream.of_string "1.0 +x");;
val token_stream : Genlex.token Stream.t = <abstr>
#Stream.next token_stream;;
- : Genlex.token = Float 1
#Stream.next token_stream;;
- : Genlex.token = Kwd "+"
#Stream.next token_stream;;
- : Genlex.token = Ident "x"
>>
The parser itself operates by pattern-matching on the stream of tokens. As
usual with recursive descent parsers, we use several intermediate parsing
functions to reflect the precedence and associativity of operators.
Pattern-matching over streams is more powerful than on regular data structures,
as it allows recursive calls to parsing functions inside the patterns, for
matching sub-components of the input stream. See chapter 7 for more details.
<<#let rec parse_expr = parser
# [< e1 = parse_mult; e = parse_more_adds e1 >] -> e
#and parse_more_adds e1 = parser
# [< 'Kwd "+"; e2 = parse_mult; e = parse_more_adds (Sum(e1, e2)) >] -> e
# | [< 'Kwd "-"; e2 = parse_mult; e = parse_more_adds (Diff(e1, e2)) >] -> e
# | [< >] -> e1
#and parse_mult = parser
# [< e1 = parse_simple; e = parse_more_mults e1 >] -> e
#and parse_more_mults e1 = parser
# [< 'Kwd "*"; e2 = parse_simple; e = parse_more_mults (Prod(e1, e2)) >]
-> e
# | [< 'Kwd "/"; e2 = parse_simple; e = parse_more_mults (Quot(e1, e2)) >]
-> e
# | [< >] -> e1
#and parse_simple = parser
# [< 'Ident s >] -> Var s
# | [< 'Int i >] -> Const(float i)
# | [< 'Float f >] -> Const f
# | [< 'Kwd "("; e = parse_expr; 'Kwd ")" >] -> e;;
val parse_expr : Genlex.token Stream.t -> expression = <fun>
val parse_more_adds : expression -> Genlex.token Stream.t -> expression =
<fun>
val parse_mult : Genlex.token Stream.t -> expression = <fun>
val parse_more_mults : expression -> Genlex.token Stream.t -> expression =
<fun>
val parse_simple : Genlex.token Stream.t -> expression = <fun>
>>
Composing the lexer and parser, we finally obtain a function to read an
expression from a character string:
<<#let read_expr s = parse_expr(lexer(Stream.of_string s));;
val read_expr : string -> expression = <fun>
#read_expr "2*(x+y)";;
- : expression = Prod (Const 2, Sum (Var "x", Var "y"))
>>
1.9 Standalone Caml programs
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All examples given so far were executed under the interactive system. Caml
code can also be compiled separately and executed non-interactively using the
batch compilers ocamlc or ocamlopt. The source code must be put in a file with
extension .ml. It consists of a sequence of phrases, which will be evaluated at
runtime in their order of appearance in the source file. Unlike in interactive
mode, types and values are not printed automatically; the program must call
printing functions explicitly to produce some output. Here is a sample
standalone program to print Fibonacci numbers:
<<
(* File fib.ml *)
let rec fib n =
if n < 2 then 1 else fib(n-1) + fib(n-2);;
let main () =
let arg = int_of_string Sys.argv.(1) in
print_int(fib arg);
print_newline();
exit 0;;
main ();;
>>
Sys.argv is an array of strings containing the command-line parameters.
Sys.argv.(1) is thus the first command-line parameter. The program above is
compiled and executed with the following shell commands:
<<
$ ocamlc -o fib fib.ml
$ ./fib 10
89
$ ./fib 20
10946
>>
Chapter 2 Labels and variants
*********************************
(Chapter written by Jacques Garrigue)
This chapter gives an overview of the new features in Objective Caml 3:
labels, and polymorphic variants.
2.1 Labels
*=*=*=*=*=*=
If you have a look at the standard library, you will see that function types
have annotations you did not see in the functions you defined yourself.
<<#List.map;;
- : f:('a -> 'b) -> 'a list -> 'b list = <fun>
#String.sub;;
- : string -> pos:int -> len:int -> string = <fun>
>>
Such annotations of the form name: are called labels. They are meant to
document the code, and allow more checking where needed. You can simply add
them in interfaces, just like they appear in the above types; but you can also
give names to arguments in your programs, by prefixing them with a tilde ~.
<<#let f ~x ~y = x - y;;
val f : x:int -> y:int -> int = <fun>
#let x = 3 and y = 2 in f ~x ~y;;
- : int = 1
>>
When you want to use distinct names for the variable and the label appearing
in the type, you can use a naming label of the form ~name:. This also applies
when the argument is not a variable.
<<#let f ~x:x1 ~y:y1 = x1 - y1;;
val f : x:int -> y:int -> int = <fun>
#f ~x:3 ~y:2;;
- : int = 1
>>
Labels obey the same rules as other identifiers in Caml, that is you cannot
use a reserved keyword (like in or to) as label.
2.1.1 Classic mode
====================
In Objective Caml, there are two ways of using labels, either the default
classic mode, or the commuting label mode.
You need do nothing special to be in classic mode, and legacy programs
written for previous versions of Objective Caml will work with no modifications
in this mode. Indeed, all the first chapter was written in this mode.
In the classic mode, labels need not be explicitly written in function
applications, but whenever they are given they are checked against the labels
in the function type.
<<#f 3 2;;
- : int = 1
#f ~x:3 ~z:2;;
Expecting function has type y:int -> int
This argument cannot be applied with label ~z
>>
The above error message gives the the type of the function applied to its
previous arguments (here x), and the position of the unexpected argument.
Similar processing is done for functions defined inside an application. If
you define inline a function with labels, they are checked against the labels
expected by the enclosing function.
<<#Hashtbl.iter;;
- : f:(key:'a -> data:'b -> unit) -> ('a, 'b) Hashtbl.t -> unit = <fun>
#let print_all tbl =
# Hashtbl.iter ~f:(fun ~key ~data -> Printf.printf "%s: %s\n" key data)
tbl;;
val print_all : (string, string) Hashtbl.t -> unit = <fun>
#let print_all tbl =
# Hashtbl.iter ~f:(fun ~data ~key -> Printf.printf "%s: %s\n" key data)
tbl;;
This function should have type key:'a -> data:'b -> unit
but its first argument is labeled ~data
>>
2.1.2 Optional arguments
==========================
An interesting feature of labeled arguments is that they can be made
optional. For optional parameters, the question mark ? replaces the tilde ~ of
non-optional ones, and the label is also prefixed by ? in the function type.
Default values may be given for such optional parameters.
<<#let bump ?(step = 1) x = x + step;;
val bump : ?step:int -> int -> int = <fun>
#bump 2;;
- : int = 3
#bump ~step:3 2;;
- : int = 5
>>
A function taking some optional arguments must also take at least one
non-labeled argument. This is because the criterion for deciding whether an
optional has been omitted is the application on a non-labeled argument
appearing after this optional argument in the function type.
<<#let test ?(x = 0) ?(y = 0) () ?(z = 0) () = (x, y, z);;
val test : ?x:int -> ?y:int -> unit -> ?z:int -> unit -> int * int * int =
<fun>
#test ();;
- : ?z:int -> unit -> int * int * int = <fun>
#test ~x:2 () ~z:3 ();;
- : int * int * int = 2, 0, 3
>>
Optional arguments behave similarly in classic and commuting label mode.
Omitting the label of an optional argument is not allowed, and in both cases
commutation between differently labeled optional arguments may occur.
<<#test ~y:2 ~x:3 () ();;
- : int * int * int = 3, 2, 0
>>
Optional arguments are actually implemented as option types. If you do not
give a default value, you have access to their internal representation, type 'a
option = None | Some of 'a. You can then provide different behaviors when an
argument is present or not.
<<#let bump ?step x =
# match step with
# | None -> x * 2
# | Some y -> x + y
#;;
val bump : ?step:int -> int -> int = <fun>
>>
It may also be useful to relay a functional argument from a function call to
another. This can be done by prefixing the applied argument with ?. This
question mark disables the wrapping of optional argument in an option type.
<<#let test2 ?x ?y () = test ?x ?y () ();;
val test2 : ?x:int -> ?y:int -> unit -> int * int * int = <fun>
#test2 ?x:None;;
- : ?y:int -> unit -> int * int * int = <fun>
>>
2.1.3 Labels and type inference
=================================
While they provide an increased comfort for writing function applications,
labels and optional arguments have the pitfall that they cannot be inferred as
completely as the rest of the language.
You can see it in the following example.
<<#let bump_it bump x =
# bump ~step:2 x;;
val bump_it : (step:int -> 'a -> 'b) -> 'a -> 'b = <fun>
#bump_it bump 1;;
This expression has type ?step:int -> int -> int but is here used with type
int -> int -> 'a
>>
While we intended the argument bump to be of type ?step:int -> int -> int,
it is inferred as step:int -> 'a -> 'b. These two types being incompatible
(internally normal and optional arguments are different), a type error occurs
when applying bump_it to the real bump.
We will not try here to explain in detail how type inference works. One must
just understand that there is not enough information in the above program to
deduce the correct type of bump. That is, there is no way to know whether an
argument is optional or not, or which is the correct order (for commuting label
mode), by looking only at how a function is applied. The strategy used by the
compiler is to assume that there are no optional arguments, and that
applications are done in the right order.
The right way to solve this problem is to add a type annotation to the
argument bump.
<<#let bump_it (bump : ?step:int -> int -> int) x =
# bump ~step:2 x;;
val bump_it : (?step:int -> int -> int) -> int -> int = <fun>
#bump_it bump 1;;
- : int = 3
>>
In practive, such problems appear mostly when using objects whose methods
have optional arguments, so that writing the type of object arguments is often
a good idea.
Normally the compiler generates a type error if you attempt to pass to a
function a parameter whose type is different from the expected one. However, in
the specific case where the expected type is a non-labeled function type, and
the argument is a function expecting optional parameters, the compiler will
attempt to transform the argument to have it match the expected type, by
passing None for all optional parameters.
<<#let twice f (x : int) = f(f x);;
val twice : (int -> int) -> int -> int = <fun>
#twice bump 2;;
- : int = 8
>>
This transformation is coherent with the intended semantics, including
side-effects. That is, if the application of optional parameters shall produce
side-effects, these are delayed until the received function is really applied
to an argument.
2.1.4 Commuting label mode
============================
The commuting label mode allows a freer syntax, at the constraint that you
must write all labels both in function definition and application, and that
labels must match in all types.
If this is your first reading of this tutorial, or if you are satisfied with
classic mode, you can probably skip the rest of this section. You need not know
anything more on labels. In particular, you should not be bothered by the fact
that some libraries are written in commuting label mode: the mode in which a
library is written and the mode in which one uses it are completely
independent.
You can switch to commuting label mode giving the -labels flag to the various
Objective Caml compilers. At the toplevel, you can also switch from classic
mode to commuting label mode, and back, with the #labels pragma.
<<##labels true;;
>>
In commuting label mode, formal parameters and arguments are only matched
according to their respective labels. This allows commuting arguments in
applications. One can also partially apply a function on any argument, creating
a new function of the remaining parameters.
<<#let f ~x ~y = x - y;;
val f : x:int -> y:int -> int = <fun>
#f ~y:2 ~x:3;;
- : int = 1
#List.fold_left [1;2;3] ~init:0 ~f:(+);;
- : int = 6
#List.fold_left ~init:0;;
- : f:(int -> 'a -> int) -> 'a list -> int = <fun>
>>
Optional parameters may also commute with non-optional or unlabelled ones.
<<#test () () ~z:1 ~y:2 ~x:3;;
- : int * int * int = 3, 2, 1
>>
As described in section 2.1.3, for out-of-order applications, the type of the
function must be known previous to the application, otherwise an incompatible
out-of-order type will be generated.
<<#let h g = g ~y:2 ~x:3;;
val h : (y:int -> x:int -> 'a) -> 'a = <fun>
#h f;;
This expression has type x:int -> y:int -> int but is here used with type
y:int -> x:int -> 'a
>>
If in a function several arguments bear the same label (or no label), they
will not commute among themselves, and order matters. But they can still
commute with other arguments.
<<#let hline ~x:x1 ~x:x2 ~y = (x1, x2, y);;
val hline : x:'a -> x:'b -> y:'c -> 'a * 'b * 'c = <fun>
#hline ~x:3 ~y:2 ~x:5;;
- : int * int * int = 3, 5, 2
>>
2.1.5 Suggestions for labeling
================================
Like for names, choosing labels for functions is not an easy task. A good
labeling is a labeling which
- makes programs more readable,
- is easy to remember,
- when possible, allows useful partial applications.
We explain here the rules we applied when labeling Objective Caml libraries.
To speak in an ``object-oriented'' way, one can consider that each function
has a main argument, its object, and other arguments related with its action,
the parameters. To permit the combination of functions through functionals in
commuting label mode, the object will not be labeled. Its role is clear by the
function itself. The parameters are labeled with names reminding either of
their nature or role. Best labels combine in their meaning nature and role.
When this is not possible the role is to prefer, since the nature will often be
given by the type itself. Obscure abbreviations should be avoided.
<<List.map : f:('a -> 'b) -> 'a list -> 'b list
output : out_channel -> buf:string -> pos:int -> len:int -> unit
>>
When there are several objects of same nature and role, they are all left
unlabeled.
<<List.iter2 : f:('a -> 'b -> 'c) -> 'a list -> 'b list -> unit
>>
When there is no preferable object, all arguments are labeled.
<<Sys.rename : src:string -> dst:string -> unit
String.blit :
src:string -> src_pos:int -> dst:string -> dst_pos:int -> len:int -> unit
>>
However, when there is only one argument, it is often left unlabeled.
<<Format.open_hvbox : int -> unit
>>
In the standard library, this principle also applies to functions of two or
three arguments, as long as their role is clear from the function's name.
Here are some of the label names you will find throughout the libraries.
------------------------------------------------------
|Label| Meaning |
------------------------------------------------------
|f: |a function to be applied |
|pos: |a position in a string or array |
|len: |a length |
|buf: |a string used as buffer |
|src: |the source of an operation |
|dst: |the destination of an operation |
|cmp: |a comparison function, e.g. Pervasives.compare|
|key: |a value used as index |
|data:|a value associated to an index |
|mode:|an operation mode or a flag list |
|perm:|file permissions |
|ms: |a duration in milliseconds |
------------------------------------------------------
All these are only suggestions, but one shall keep in mind that the choice of
labels is essential for readability. Bizarre choices will make the program
harder to maintain.
In the ideal, the right function name with right labels shall be enough to
understand the function's meaning. Since one can get this information with
OCamlBrowser or the ocaml toplevel, the documentation is only used when a more
detailed specification is needed.
2.2 Polymorphic variants
*=*=*=*=*=*=*=*=*=*=*=*=*=
Variants as presented in section 1.4 are a powerful tool to build data
structures and algorithms. However they sometimes lack flexibility when used in
modular programming. This is due to the fact every constructor reserves a name
to be used with a unique type. On cannot use the same name in another type, or
consider a value of some type to belong to some other type with more
constructors.
With polymorphic variants, this original assumption is removed. That is, a
variant tag does not belong to any type in particular, the type system will
just check that it is an admissible value according to its use. You need not
define a type before using a variant tag. A variant type will be inferred
independently for each of its uses.
Basic use
=========
In programs, polymorphic variants work like usual ones. You just have to
prefix their names with a backquote character `.
<<#[`On; `Off];;
- : [> `On | `Off] list = [`On; `Off]
#`Number 1;;
- : [> `Number of int] = `Number 1
#let f = function `On -> 1 | `Off -> 0 | `Number n -> n;;
val f : [< `On | `Off | `Number of int] -> int = <fun>
#List.map ~f [`On; `Off];;
- : int list = [1; 0]
>>
[>`Off|`On] list means that to match this list, you should at least be able
to match `Off and `On, without argument. [<`On|`Off|`Number of int] means that
f may be applied to `Off, `On (both without argument), or `Number n where n is
an integer. The > and < inside the variant type shows that they may still be
refined, either by defining more tags or allowing less. As such they contain an
implicit type variable. Both variant types appearing only once in the type, the
implicit type variables they constrain are not shown.
The above variant types were polymorphic, allowing further refinement. When
writing type annotations, one will most often describe fixed variant types,
that is types that can be no longer refined. This is also the case for type
abbreviations. Such types do not contain < or >, but just an enumeration of the
tags and their associated types, just like in a normal datatype definition.
<<#type 'a vlist = [`Nil | `Cons of 'a * 'a vlist];;
type 'a vlist = [ `Nil | `Cons of 'a * 'a vlist]
#let rec map ~f : 'a vlist -> 'b vlist = function
# | `Nil -> `Nil
# | `Cons(a, l) -> `Cons(f a, map ~f l)
#;;
val map : f:('a -> 'b) -> 'a vlist -> 'b vlist = <fun>
>>
Advanced use
============
Type-checking polymorphic variants is a subtle thing, and some expressions
may result in more complex type information.
<<#let f = function `A -> `C | `B -> `D | x -> x;;
val f : ([> `C | `D | `A | `B] as 'a) -> 'a = <fun>
#f `E;;
- : _[> `C | `D | `A | `B | `E] = `E
>>
Here we are seeing two phenomena. First, since this matching is open (the
last case catches any tag), we obtain the type [> `A | `B] rather than [< `A |
`B] in a closed matching. Then, since x is returned as is, input and return
types are identical. The notation as 'a denotes such type sharing. If we apply
f to yet another tag `E, it gets added to the list.
<<#let f1 = function `A x -> x = 1 | `B -> true | `C -> false
#let f2 = function `A x -> x = "a" | `B -> true ;;
val f1 : [< `A of int | `B | `C] -> bool = <fun>
val f2 : [< `A of string | `B] -> bool = <fun>
#let f x = f1 x && f2 x;;
val f : [< `A of string & int | `B] -> bool = <fun>
>>
Here f1 and f2 both accept the variant tags `A and `B, but the argument of
`A is int for f1 and string for f2. In f's type `C, only accepted by f1,
disappears, but both argument types appear for `A as int & string. This means
that if we pass the variant tag `A to f, its argument should be both int and
string. Since there is no such value, f cannot be applied to `A, and `B is the
only accepted input.
Even if a value has a fixed variant type, one can still give it a larger type
through coercions. Coercions are normally written with both the source type and
the destination type, but in simple cases the source type may be omitted.
<<#type 'a wlist = [`Nil | `Cons of 'a * 'a wlist | `Snoc of 'a wlist * 'a];;
type 'a wlist = [ `Nil | `Cons of 'a * 'a wlist | `Snoc of 'a wlist * 'a]
#let wlist_of_vlist l = (l : 'a vlist :> 'a wlist);;
val wlist_of_vlist : 'a vlist -> 'a wlist = <fun>
#fun x -> (x :> [`A|`B|`C]);;
- : [< `A | `B | `C] -> [ `A | `B | `C] = <fun>
>>
You may also selectively coerce values through pattern matching.
<<#let split_cases = function
# | `Nil | `Cons _ as x -> `A x
# | `Snoc _ as x -> `B x
#;;
val split_cases :
[< `Nil | `Cons of 'a | `Snoc of 'b] ->
[> `A of [> `Nil | `Cons of 'a] | `B of [> `Snoc of 'b]] = <fun>
>>
When an or-pattern composed of variant tags is wrapped inside an
alias-pattern, the alias is given a type containing only the tags enumerated in
the or-pattern. This allows for many useful idioms, like incremental definition
of functions.
<<#let num x = `Num x
#let eval1 eval (`Num x) = x
#let rec eval x = eval1 eval x ;;
val num : 'a -> [> `Num of 'a] = <fun>
val eval1 : 'a -> [< `Num of 'b] -> 'b = <fun>
val eval : [< `Num of 'a] -> 'a = <fun>
#let plus x y = `Plus(x,y)
#let eval2 eval = function
# | `Plus(x,y) -> eval x + eval y
# | `Num _ as x -> eval1 eval x
#let rec eval x = eval2 eval x ;;
val plus : 'a -> 'b -> [> `Plus of 'a * 'b] = <fun>
val eval2 : ('a -> int) -> [< `Plus of 'a * 'a | `Num of int] -> int = <fun>
val eval : ([< `Plus of 'a * 'a | `Num of int] as 'a) -> int = <fun>
>>
To make this even more confortable, you may use type definitions as
abbreviations for or-patterns. That is, if you have defined type myvariant =
[`Tag1 int | `Tag2 bool], then the pattern #myvariant is equivalent to writing
(`Tag1(_ : int) | `Tag2(_ : bool)).
Such abbreviations may be used alone,
<<#let f = function
# | #myvariant -> "myvariant"
# | `Tag3 -> "Tag3";;
val f : [< `Tag1 of int | `Tag2 of bool | `Tag3] -> string = <fun>
>>
or combined with with aliases.
<<#let g1 = function `Tag1 _ -> "Tag1" | `Tag2 _ -> "Tag2";;
val g1 : [< `Tag1 of 'a | `Tag2 of 'b] -> string = <fun>
#let g = function
# | #myvariant as x -> g1 x
# | `Tag3 -> "Tag3";;
val g : [< `Tag1 of int | `Tag2 of bool | `Tag3] -> string = <fun>
>>
2.2.1 Weaknesses of polymorphic variants
==========================================
After seeing the power of polymorphic variants, one may wonder why they were
added to core language variants, rather than replacing them.
The answer is two fold. One first aspect is that while being pretty
efficient, the lack of static type information allows for less optimizations,
and makes polymorphic variants slightly heavier than core language ones.
However noticeable differences would only appear on huge data structures.
More important is the fact that polymorphic variants, while being type-safe,
result in a weaker type discipline. That is, core language variants do actually
much more than ensuring type-safety, they also check that you use only declared
constructors, that all constructors present in a data-structure are compatible,
and they enforce typing constraints to their parameters.
For this reason, you must be more careful about making types explicit when
you use polymorphic variants. When you write a library, this is easy since you
can describe exact types in interfaces, but for simple programs you are
probably better off with core language variants.
Beware also that certain idioms make trivial errors very hard to find. For
instance, the following code is probably wrong but the compiler has no way to
see it.
<<#type abc = [`A | `B | `C] ;;
type abc = [ `A | `B | `C]
#let f = function
# | `As -> "A"
# | #abc -> "other" ;;
val f : [< `As | `A | `B | `C] -> string = <fun>
#let f : abc -> string = f ;;
val f : abc -> string = <fun>
>>
You can avoid such risks by annotating the definition itself.
<<#let f : abc -> string = function
# | `As -> "A"
# | #abc -> "other" ;;
This pattern matches values of type [< `As | `A | `B | `C]
but is here used to match values of type abc = [ `A | `B | `C]
>>
Chapter 3 Objects in Caml
*****************************
(Chapter written by Jérôme Vouillon and Didier Rémy)
This chapter gives an overview of the object-oriented features of Objective
Caml.
3.1 Classes and objects
3.2 Reference to self
3.3 Initializers
3.4 Virtual methods
3.5 Private methods
3.6 Class interfaces
3.7 Inheritance
3.8 Multiple inheritance
3.9 Parameterized classes
3.10 Using coercions
3.11 Functional objects
3.12 Cloning objects
3.13 Recursive classes
3.14 Binary methods
3.15 Friends
3.1 Classes and objects
*=*=*=*=*=*=*=*=*=*=*=*=*
The class point has one instance variable x and two methods get_x and move.
The initial value of the instance variable is 0. The variable x is declared
mutable, so the method move can change its value.
<<#class point =
# object
# val mutable x = 0
# method get_x = x
# method move d = x <- x + d
# end;;
class point :
object val mutable x : int method get_x : int method move : int -> unit end
>>
We now create a new point p.
<<#let p = new point;;
val p : point = <obj>
>>
Note that the type of p is point. This is an abbreviation automatically
defined by the class definition above. It stands for the object type <get_x :
int; move : int -> unit>, listing the methods of class point along with their
types.
Let us apply some methods to p:
<<#p#get_x;;
- : int = 0
#p#move 3;;
- : unit = ()
#p#get_x;;
- : int = 3
>>
The evaluation of the body of a class only takes place at object creation
time. Therefore, in the following example, the instance variable x is
initialized to different values for two different objects.
<<#let x0 = ref 0;;
val x0 : int ref = {contents=0}
#class point =
# object
# val mutable x = incr x0; !x0
# method get_x = x
# method move d = x <- x + d
# end;;
class point :
object val mutable x : int method get_x : int method move : int -> unit end
#new point#get_x;;
- : int = 1
#new point#get_x;;
- : int = 2
>>
The class point can also be abstracted over the initial values of points.
<<#class point = fun x_init ->
# object
# val mutable x = x_init
# method get_x = x
# method move d = x <- x + d
# end;;
class point :
int ->
object val mutable x : int method get_x : int method move : int -> unit end
>>
As for declaration of functions, the above definition can be abbreviated as:
<<#class point x_init =
# object
# val mutable x = x_init
# method get_x = x
# method move d = x <- x + d
# end;;
class point :
int ->
object val mutable x : int method get_x : int method move : int -> unit end
>>
An instance of the class point is now a function that expects an initial
parameter to create a point object:
<<#new point;;
- : int -> point = <fun>
#let p = new point 7;;
val p : point = <obj>
>>
The parameter x_init is, of course, visible in the whole body of the
definition, including methods. For instance, the method get_offset in the class
below returns the position of the object to the origin.
<<#class point x_init =
# object
# val mutable x = x_init
# method get_x = x
# method get_offset = x - x_init
# method move d = x <- x + d
# end;;
class point :
int ->
object
val mutable x : int
method get_offset : int
method get_x : int
method move : int -> unit
end
>>
Expressions can be evaluated and bound before defining the object body of
the class. This is useful to enforce invariants. For instance, points can be
automatically adjusted to grid as follows:
<<#class adjusted_point x_init =
# let origin = (x_init / 10) * 10 in
# object
# val mutable x = origin
# method get_x = x
# method get_offset = x - origin
# method move d = x <- x + d
# end;;
class adjusted_point :
int ->
object
val mutable x : int
method get_offset : int
method get_x : int
method move : int -> unit
end
>>
(One could also raise an exception if the x_init coordinate is not on the
grid.) In fact, the same effect could here be obtained by calling the
definition of class point with the value of the origin.
<<#class adjusted_point x_init = point ((x_init / 10) * 10);;
class adjusted_point : int -> point
>>
An alternative solution would have been to define the adjustment in a
special allocation function:
<<#let new_adjusted_point x_init = new point ((x_init / 10) * 10);;
val new_adjusted_point : int -> point = <fun>
>>
However, the former pattern is generally more appropriate, since the code
for adjustment is part of the definition of the class and will be inherited.
This ability provides class constructors as can be found in other languages.
Several constructors can be defined this way to build objects of the same class
but with different initialization patterns; an alternative is to use
initializers, as decribed below in section 3.3.
3.2 Reference to self
*=*=*=*=*=*=*=*=*=*=*=*
A method can also send messages to self (that is, the current object). For
that, self must be explicitly bound, here to the variable s (s could be any
identifier, even though we will often choose the name self.)
<<#class printable_point x_init =
# object (s)
# val mutable x = x_init
# method get_x = x
# method move d = x <- x + d
# method print = print_int s#get_x
# end;;
class printable_point :
int ->
object
val mutable x : int
method get_x : int
method move : int -> unit
method print : unit
end
#let p = new printable_point 7;;
val p : printable_point = <obj>
#p#print;;
7- : unit = ()
>>
Dynamically, the variable s is bound at the invocation of a method. In
particular, when the class printable_point will be inherited, the variable s
will be correctly bound to the object of the subclass.
3.3 Initializers
*=*=*=*=*=*=*=*=*=
Let-bindings within class definitions are evaluated before the object is
constructed. It is also possible to evaluate an expression immediately after
the object has been built. Such code is written as an anonymous hidden method
called an initializer. Therefore, is can access self and the instance
variables.
<<#class printable_point x_init =
# let origin = (x_init / 10) * 10 in
# object (self)
# val mutable x = origin
# method get_x = x
# method move d = x <- x + d
# method print = print_int self#get_x
# initializer print_string "new point at "; self#print; print_newline()
# end;;
class printable_point :
int ->
object
val mutable x : int
method get_x : int
method move : int -> unit
method print : unit
end
#let p = new printable_point 17;;
new point at 10
val p : printable_point = <obj>
>>
Initializers cannot be overridden. On the contrary, all initializers are
evaluated sequentially. Initializers are particularly useful to enforce
invariants. Another example can be seen in section 5.1.
3.4 Virtual methods
*=*=*=*=*=*=*=*=*=*=*
It is possible to declare a method without actually defining it, using the
keyword virtual. This method will be provided latter in subclasses. A class
containing virtual methods must be flagged virtual, and cannot be instantiated
(that is, no object of this class can be created). It still defines
abbreviations (treating virtual methods as other methods.)
<<#class virtual abstract_point x_init =
# object (self)
# val mutable x = x_init
# method virtual get_x : int
# method get_offset = self#get_x - x_init
# method virtual move : int -> unit
# end;;
class virtual abstract_point :
int ->
object
val mutable x : int
method get_offset : int
method virtual get_x : int
method virtual move : int -> unit
end
#class point x_init =
# object
# inherit abstract_point x_init
# method get_x = x
# method move d = x <- x + d
# end;;
class point :
int ->
object
val mutable x : int
method get_offset : int
method get_x : int
method move : int -> unit
end
>>
3.5 Private methods
*=*=*=*=*=*=*=*=*=*=*
Private methods are methods that do not appear in object interfaces. They can
only be invoked from other methods of the same object.
<<#class restricted_point x_init =
# object (self)
# val mutable x = x_init
# method get_x = x
# method private move d = x <- x + d
# method bump = self#move 1
# end;;
class restricted_point :
int ->
object
val mutable x : int
method bump : unit
method get_x : int
method private move : int -> unit
end
#let p = new restricted_point 0;;
val p : restricted_point = <obj>
#p#move 10;;
This expression has type restricted_point
It has no method move
#p#bump;;
- : unit = ()
>>
Private methods are inherited (they are by default visible in subclasses),
unless they are hidden by signature matching, as described below.
Private methods can be made public in a subclass.
<<#class point_again x =
# object (self)
# inherit restricted_point x
# method virtual move : _
# end;;
class point_again :
int ->
object
val mutable x : int
method bump : unit
method get_x : int
method move : int -> unit
end
>>
The annotation virtual here is only used to mentioned a method without
providing its definition. An alternative definition is
<<#class point_again x =
# object (self : < move : _; ..> )
# inherit restricted_point x
# end;;
class point_again :
int ->
object
val mutable x : int
method bump : unit
method get_x : int
method move : int -> unit
end
>>
One could think that a private method should remain private in a subclass.
However, since the method is visible in a subclass, it is always possible pick
it's code and define a method of the same name that run that code, so yet
another (heavier) solution would be:
<<#class point_again x =
# object (self : < move : _; ..> )
# inherit restricted_point x as super
# method move = super#move
# end;;
class point_again :
int ->
object
val mutable x : int
method bump : unit
method get_x : int
method move : int -> unit
end
>>
Of course, private methods can also be virtual. Then, the keywords must
appear in this order method private virtual.
3.6 Class interfaces
*=*=*=*=*=*=*=*=*=*=*=
Class interfaces are inferred from class definitions. They may also be
defined directly and used to restrict the type of a class. As class
declarations, they also define a new type constructor.
<<#class type restricted_point_type =
# object
# method get_x : int
# method bump : unit
#end;;
class type restricted_point_type =
object method bump : unit method get_x : int end
#fun (x : restricted_point_type) -> x;;
- : restricted_point_type -> restricted_point_type = <fun>
>>
In addition to documentation, these class interfaces can be used to
constrain the type of a class. Both instance variables and concrete private
methods can be hidden by a class type constraint. Public and virtual methods,
however, cannot.
<<#class restricted_point' x = (restricted_point x : restricted_point_type);;
class restricted_point' : int -> restricted_point_type
>>
Or, equivalently:
<<#class restricted_point' = (restricted_point : int ->
restricted_point_type);;
class restricted_point' : int -> restricted_point_type
>>
The interface of a class can also be specified in a module signature, and
used to restrict the inferred signature of a module.
<<#module type POINT = sig
# class restricted_point' : int ->
# object
# method get_x : int
# method bump : unit
# end
#end;;
module type POINT =
sig
class restricted_point' :
int -> object method bump : unit method get_x : int end
end
#module Point : POINT = struct
# class restricted_point' = restricted_point
#end;;
module Point : POINT
>>
3.7 Inheritance
*=*=*=*=*=*=*=*=*
We illustrate inheritance by defining a class of colored points that inherits
from the class of points. This class has all instance variables and all methods
of class point, plus a new instance variable c and a new method color.
<<#class colored_point x (c : string) =
# object
# inherit point x
# val c = c
# method color = c
# end;;
class colored_point :
int ->
string ->
object
val c : string
val mutable x : int
method color : string
method get_offset : int
method get_x : int
method move : int -> unit
end
#let p' = new colored_point 5 "red";;
val p' : colored_point = <obj>
#p'#get_x, p'#color;;
- : int * string = 5, "red"
>>
A point and a colored point have incompatible types, since a point has no
method color. However, the function get_x below is a generic function applying
method get_x to any object p that has this method (and possibly some others,
which are represented by an ellipsis in the type). Thus, it applies to both
points and colored points.
<<#let get_succ_x p = p#get_x + 1;;
val get_succ_x : < get_x : int; .. > -> int = <fun>
#get_succ_x p + get_succ_x p';;
- : int = 8
>>
Methods need not be declared previously, as shown by the example:
<<#let set_x p = p#set_x;;
val set_x : < set_x : 'a; .. > -> 'a = <fun>
#let incr p = set_x p (get_succ_x p);;
val incr : < get_x : int; set_x : int -> 'a; .. > -> 'a = <fun>
>>
3.8 Multiple inheritance
*=*=*=*=*=*=*=*=*=*=*=*=*=
Multiple inheritance is allowed. Only the last definition of a method is
kept: the redefinition in a subclass of a method that was visible in the parent
class overrides the definition in the parent class. Previous definitions of a
method can be reused by binding the related ancestor. Below, super is bound to
the ancestor printable_point. The name super is not actually a variable and can
only be used to select a method as in super#print.
<<#class printable_colored_point y c =
# object (self)
# val c = c
# method color = c
# inherit printable_point y as super
# method print =
# print_string "(";
# super#print;
# print_string ", ";
# print_string (self#color);
# print_string ")"
# end;;
class printable_colored_point :
int ->
string ->
object
val c : string
val mutable x : int
method color : string
method get_x : int
method move : int -> unit
method print : unit
end
#let p' = new printable_colored_point 17 "red";;
new point at (10, red)
val p' : printable_colored_point = <obj>
#p'#print;;
(10, red)- : unit = ()
>>
A private method that has been hidden in the parent class is no more
visible, and is thus not overridden. Since initializers are treated as private
methods, all initializers along the class hierarchy are evaluated, in the order
they are introduced.
3.9 Parameterized classes
*=*=*=*=*=*=*=*=*=*=*=*=*=*
Reference cells can also be implemented as objects. The naive definition
fails to typecheck:
<<#class ref x_init =
# object
# val mutable x = x_init
# method get = x
# method set y = x <- y
# end;;
Some type variables are unbound in this type:
class ref :
'a ->
object val mutable x : 'a method get : 'a method set : 'a -> unit end
The method get has type 'a where 'a is unbound
>>
The reason is that at least one of the methods has a polymorphic type (here,
the type of the value stored in the reference cell), thus the class should be
parametric, or the method type should be constrained to a monomorphic type. A
monomorphic instance of the class could be defined by:
<<#class ref (x_init:int) =
# object
# val mutable x = x_init
# method get = x
# method set y = x <- y
# end;;
class ref :
int ->
object val mutable x : int method get : int method set : int -> unit end
>>
A class for polymorphic references must explicitly list the type parameters
in its declaration. Class type parameters are always listed between [ and ].
The type parameters must also be bound somewhere in the class body by a type
constraint.
<<#class ['a] ref x_init =
# object
# val mutable x = (x_init : 'a)
# method get = x
# method set y = x <- y
# end;;
class ['a] ref :
'a -> object val mutable x : 'a method get : 'a method set : 'a -> unit end
#let r = new ref 1 in r#set 2; (r#get);;
- : int = 2
>>
The type parameter in the declaration may actually be constrained in the
body of the class definition. In the class type, the actual value of the type
parameter is displayed in the constraint clause.
<<#class ['a] ref_succ (x_init:'a) =
# object
# val mutable x = x_init + 1
# method get = x
# method set y = x <- y
# end;;
class ['a] ref_succ :
'a ->
object
constraint 'a = int
val mutable x : int
method get : int
method set : int -> unit
end
>>
Let us consider a more realistic example. We put an additional type
constraint in method move, since no free variables must remain uncaptured by a
type parameter.
<<#class ['a] circle (c : 'a) =
# object
# val mutable center = c
# method center = center
# method set_center c = center <- c
# method move = (center#move : int -> unit)
# end;;
class ['a] circle :
'a ->
object
constraint 'a = < move : int -> unit; .. >
val mutable center : 'a
method center : 'a
method move : int -> unit
method set_center : 'a -> unit
end
>>
An alternate definition of circle, using a constraint clause in the class
definition, is shown below. The type #point used below in the constraint clause
is an abbreviation produced by the definition of class point. This abbreviation
unifies with the type of any object belonging to a subclass of class point. It
actually expands to < get_x : int; move : int -> unit; .. >. This leads to the
following alternate definition of circle, which has slightly stronger
constraints on its argument, as we now expect center to have a method get_x.
<<#class ['a] circle (c : 'a) =
# object
# constraint 'a = #point
# val mutable center = c
# method center = center
# method set_center c = center <- c
# method move = center#move
# end;;
class ['a] circle :
'a ->
object
constraint 'a = #point
val mutable center : 'a
method center : 'a
method move : int -> unit
method set_center : 'a -> unit
end
>>
The class colored_circle is a specialized version of class circle which
requires the type of the center to unify with #colored_point, and adds a method
color. Note that when specializing a parameterized class, the instance of type
parameter must always be explicitly given. It is again written inside [ and ].
<<#class ['a] colored_circle c =
# object
# constraint 'a = #colored_point
# inherit ['a] circle c
# method color = center#color
# end;;
class ['a] colored_circle :
'a ->
object
constraint 'a = #colored_point
val mutable center : 'a
method center : 'a
method color : string
method move : int -> unit
method set_center : 'a -> unit
end
>>
3.10 Using coercions
*=*=*=*=*=*=*=*=*=*=*=
Subtyping is never implicit. There are, however, two ways to perform
subtyping. The most general construction is fully explicit: both the domain and
the codomain of the type coercion must be given.
We have seen that points and colored points have incompatible types. For
instance, they cannot be mixed in the same list. However, a colored point can
be coerced to a point, hiding its color method:
<<#let colored_point_to_point cp = (cp : colored_point :> point);;
val colored_point_to_point : colored_point -> point = <fun>
#let p = new point 3 and q = new colored_point 4 "blue";;
val p : point = <obj>
val q : colored_point = <obj>
#let l = [p; (colored_point_to_point q)];;
val l : point list = [<obj>; <obj>]
>>
An object of type t can be seen as an object of type t' only if t is a
subtype of t'. For instance, a point cannot be seen as a colored point.
<<#(p : point :> colored_point);;
Type point = < get_offset : int; get_x : int; move : int -> unit >
is not a subtype of type
colored_point =
< color : string; get_offset : int; get_x : int; move : int -> unit >
>>
Indeed, backward coercions are unsafe, and should be combined with a type
case, possibly raising a runtime error. However, there is no such operation
available in the language.
Be aware that subtyping and inheritance are not related. Inheritance is a
syntactic relation between classes while subtyping is a semantic relation
between types. For instance, the class of colored points could have been
defined directly, without inheriting from the class of points; the type of
colored points would remain unchanged and thus still be a subtype of points.
The domain of a coercion can usually be omitted. For instance, one can
define:
<<#let to_point cp = (cp :> point);;
val to_point :
< get_offset : int; get_x : int; move : int -> unit; .. > -> point = <fun>
>>
In this case, the function colored_point_to_point is an instance of the
function to_point. This is not always true, however. The fully explicit
coercion is more precise and is sometimes unavoidable. Here is an example
where the shorter form fails:
<<#class virtual c = object method virtual m : c end;;
class virtual c : object method virtual m : c end
#class c' =
# object (self)
# inherit c
# method m = (self :> c)
# method m' = 1
#end;;
class c' : object method m : c method m' : int end
>>
The type of the coercion to type c can be seen here:
<<#function x -> (x :> c);;
- : < m : c; .. > -> c = <fun>
>>
As class c' inherits from class c, its method m must have type c. On the
other hand, in expression (self :> c) the type of self and the domain of the
coercion above must be unified. That is, the type of the method m in self
(i.e. c) is also the type of self. So, the type of self is c. This is a
contradiction, as the type of self has a method m', whereas type c does not.
The desired coercion of type <m : c;..> -> c can be obtained by using a fully
explicit coercion:
<<#function x -> (x : #c :> c);;
- : #c -> c = <fun>
>>
Thus one can define class c' as follows:
<<#class c' =
# object (self)
# inherit c
# method m = (self : #c :> c)
# method m' = 1
# end;;
class c' : object method m : c method m' : int end
>>
An alternative is to define class c this way (of course this definition is
not equivalent to the previous one):
<<#class virtual c = object (_ : 'a) method virtual m : 'a end;;
class virtual c : object ('a) method virtual m : 'a end
>>
Then, a coercion operator is not even required.
<<#class c' = object (self) inherit c method m = self method m' = 1 end;;
class c' : object ('a) method m : 'a method m' : int end
>>
Here, the simple coercion operator (e :> c) can be used to coerce an object
expression e from type c' to type c. Semi-implicit coercions are actually
defined so as to work correctly with classes returning self.
<<#(new c' :> c);;
- : c = <obj>
>>
Another common problem may occur when one tries to define a coercion to a
class c inside the definition of class c. The problem is due to the type
abbreviation not being completely defined yet, and so its subtypes are not
clearly known. Then, a coercion (_ : #c :> c) is taken to be the identity
function, as in
<<#function x -> (x :> 'a);;
- : 'a -> 'a = <fun>
>>
As a consequence, if the coercion is applied to self, as in the following
example, the type of self is unified with the closed type c (a closed object
type is an object type without ellipsis). This would constrains the type of
self be closed and is thus rejected. Indeed, the type of self cannot be closed:
this would prevent any further extension of the class. Therefore, a type error
is generated when the unification of this type with another type would result
in a closed object type.
<<#class c = object (self) method m = (self : #c :> c) end;;
This expression has type < m : 'a; .. > but is here used with type c = < .. >
Self type cannot escape its class
>>
This problem can sometimes be avoided by first defining the abbreviation,
using a class type:
<<#class type c0 = object method m : c0 end;;
class type c0 = object method m : c0 end
#class c : c0 = object (self) method m = (self : #c0 :> c0) end;;
class c : c0
>>
It is also possible to use a virtual class. Inheriting from this class
simultaneously allows to enforce all methods of c to have the same type as the
methods of c0.
<<#class virtual c0 = object method virtual m : c0 end;;
class virtual c0 : object method virtual m : c0 end
#class c = object (self) inherit c0 method m = (self : #c0 :> c0) end;;
class c : object method m : c0 end
>>
One could think of defining the type abbreviation directly:
<<#type c1 = <m : c1>;;
type c1 = < m : c1 >
>>
However, the abbreviation #c0 cannot be defined directly in a similar It can
only be defined by a class or a classtyped definition. (One reason is that #
sharp abbreviations carry an implicit anonymous variable .. that cannot be
explicitly named). Thus, the abbreviation #c0 should be expanded:
<<#class c = object (self) method m = (self : <m : c1; ..> as 'a :> c1) end;;
class c : object method m : c1 end
>>
3.11 Functional objects
*=*=*=*=*=*=*=*=*=*=*=*=*
It is possible to write a version of class point without assignments on the
instance variables. The construct {< ... >} returns a copy of ``self'' (that
is, the current object), possibly changing the value of some instance
variables.
<<#class functional_point y =
# object
# val x = y
# method get_x = x
# method move d = {< x = x + d >}
# end;;
class functional_point :
int ->
object ('a) val x : int method get_x : int method move : int -> 'a end
#let p = new functional_point 7;;
val p : functional_point = <obj>
#p#get_x;;
- : int = 7
#(p#move 3)#get_x;;
- : int = 10
#p#get_x;;
- : int = 7
>>
Note that the type abbreviation functional_point is recursive, which can be
seen in the class type of functional_point: the type of self is 'a and 'a
appears inside the type of the method move.
The above definition of functional_point is not equivalent to the following:
<<#class bad_functional_point y =
# object
# val x = y
# method get_x = x
# method move d = new functional_point (x+d)
# end;;
class bad_functional_point :
int ->
object
val x : int
method get_x : int
method move : int -> functional_point
end
#let p = new functional_point 7;;
val p : functional_point = <obj>
#p#get_x;;
- : int = 7
#(p#move 3)#get_x;;
- : int = 10
#p#get_x;;
- : int = 7
>>
While objects of either class will behave the same, objects of their
subclasses will be different. In a subclass of the latter, the method move will
keep returning an object of the parent class. On the contrary, in a subclass of
the former, the method move will return an object of the subclass.
Functional update is often used in conjunction with binary methods as
illustrated in section 5.2.1.
3.12 Cloning objects
*=*=*=*=*=*=*=*=*=*=*=
Objects can also be cloned, whether they are functional or imperative. The
library function Oo.copy makes a shallow copy of an object. That is, it
returns an object that is equal to the previous one. The instance variables
have been copied but their contents are shared. Assigning a new value to an
instance variable of the copy (using a method call) will not affect instance
variables of the original, and conversely. A deeper assignment (for example if
the instance variable if a reference cell) will of course affect both the
original and the copy.
The type of Oo.copy is the following:
<<#Oo.copy;;
- : (< .. > as 'a) -> 'a = <fun>
>>
The keyword as in that type binds the type variable 'a to the object type <
.. >. Therefore, Oo.copy takes an object with any methods (represented by the
ellipsis), and returns an object of the same type. The type of Oo.copy is
different from type < .. > -> < .. > as each ellipsis represents a different
set of methods. Ellipsis actually behaves as a type variable.
<<#let p = new point 5;;
val p : point = <obj>
#let q = Oo.copy p;;
val q : point = <obj>
#q#move 7; (p#get_x, q#get_x);;
- : int * int = 5, 12
>>
In fact, Oo.copy p will behave as p#copy assuming that a public method copy
with body {< >} has been defined in the class of p.
Objects can be compared using the generic comparison functions = and <>. Two
objects are equal if and only if they are physically equal. In particular, an
object and its copy are not equal.
<<#let q = Oo.copy p;;
val q : point = <obj>
#p = q, p = p;;
- : bool * bool = false, true
>>
Other generic comparissons such as (<, <=,...) can also be used on objects.
The relation < defines an unspecified but strict ordering on objets. The
ordering relationship between two objects is fixed once for all after the two
objects have been created and it is not affected by mutation of fields.
Cloning and override have a non empty intersection. They are interchangeable
when used within an object and without overriding any field:
<<#class copy =
# object
# method copy = {< >}
# end;;
class copy : object ('a) method copy : 'a end
#class copy =
# object (self)
# method copy = Oo.copy self
# end;;
class copy : object ('a) method copy : 'a end
>>
Only the override can be used to actually override fields, and only the
Oo.copy primitive can be used externally.
Cloning can also be used to provide facilities for saving and restoring the
state of objects.
<<#class backup =
# object (self : 'mytype)
# val mutable copy = None
# method save = copy <- Some {< copy = None >}
# method restore = match copy with Some x -> x | None -> self
# end;;
class backup :
object ('a)
val mutable copy : 'a option
method restore : 'a
method save : unit
end
>>
The above definition will only backup one level. The backup facility can be
added to any class using multiple inheritance.
<<#class ['a] backup_ref x = object inherit ['a] ref x inherit backup end;;
class ['a] backup_ref :
'a ->
object ('b)
val mutable copy : 'b option
val mutable x : 'a
method get : 'a
method restore : 'b
method save : unit
method set : 'a -> unit
end
#let rec get p n = if n = 0 then p # get else get (p # restore) (n-1);;
val get : (< get : 'b; restore : 'a; .. > as 'a) -> int -> 'b = <fun>
#let p = new backup_ref 0 in
#p # save; p # set 1; p # save; p # set 2;
#[get p 0; get p 1; get p 2; get p 3; get p 4];;
- : int list = [2; 1; 1; 1; 1]
>>
A variant of backup could retain all copies. (We then add a method clear to
manually erase all copies.)
<<#class backup =
# object (self : 'mytype)
# val mutable copy = None
# method save = copy <- Some {< >}
# method restore = match copy with Some x -> x | None -> self
# method clear = copy <- None
# end;;
class backup :
object ('a)
val mutable copy : 'a option
method clear : unit
method restore : 'a
method save : unit
end
>>
<<#class ['a] backup_ref x = object inherit ['a] ref x inherit backup end;;
class ['a] backup_ref :
'a ->
object ('b)
val mutable copy : 'b option
val mutable x : 'a
method clear : unit
method get : 'a
method restore : 'b
method save : unit
method set : 'a -> unit
end
#let p = new backup_ref 0 in
#p # save; p # set 1; p # save; p # set 2;
#[get p 0; get p 1; get p 2; get p 3; get p 4];;
- : int list = [2; 1; 0; 0; 0]
>>
3.13 Recursive classes
*=*=*=*=*=*=*=*=*=*=*=*=
Recursive classes can be used to define objects whose types are mutually
recursive.
<<#class window =
# object
# val mutable top_widget = (None : widget option)
# method top_widget = top_widget
# end
#and widget (w : window) =
# object
# val window = w
# method window = window
# end;;
class window :
object
val mutable top_widget : widget option
method top_widget : widget option
end
class widget :
window -> object val window : window method window : window end
>>
Although their types are mutually recursive, the classes widget and window
are themselves independent.
3.14 Binary methods
*=*=*=*=*=*=*=*=*=*=*
A binary method is a method which takes an argument of the same type as self.
The class comparable below is a template for classes with a binary method leq
of type 'a -> bool where the type variable 'a is bound to the type of self.
Therefore, #comparable expands to < leq : 'a -> bool; .. > as 'a. We see here
that the binder as also allows to write recursive types.
<<#class virtual comparable =
# object (_ : 'a)
# method virtual leq : 'a -> bool
# end;;
class virtual comparable : object ('a) method virtual leq : 'a -> bool end
>>
We then define a subclass money of comparable. The class money simply wraps
floats as comparable objects. We will extend it below with more operations.
There is a type constraint on the class parameter x as the primitive <= is a
polymorphic comparison function in Objective Caml. The inherit clause ensures
that the type of objects of this class is an instance of #comparable.
<<#class money (x : float) =
# object
# inherit comparable
# val repr = x
# method value = repr
# method leq p = repr <= p#value
# end;;
class money :
float ->
object ('a)
val repr : float
method leq : 'a -> bool
method value : float
end
>>
Note that the type money1 is not a subtype of type comparable, as the self
type appears in contravariant position in the type of method leq. Indeed, an
object m of class money has a method leq that expects an argument of type money
since it accesses its value method. Considering m of type comparable would
allow to call method leq on m with an argument that does not have a method
value, which would be an error.
Similarly, the type money2 below is not a subtype of type money.
<<#class money2 x =
# object
# inherit money x
# method times k = {< repr = k *. repr >}
# end;;
class money2 :
float ->
object ('a)
val repr : float
method leq : 'a -> bool
method times : float -> 'a
method value : float
end
>>
It is however possible to define functions that manipulate objects of type
either money or money2: the function min will return the minimum of any two
objects whose type unifies with #comparable. The type of min is not the same as
#comparable -> #comparable -> #comparable, as the abbreviation #comparable
hides a type variable (an ellipsis). Each occurrence of this abbreviation
generates a new variable.
<<#let min (x : #comparable) y =
# if x#leq y then x else y;;
val min : (#comparable as 'a) -> 'a -> 'a = <fun>
>>
This function can be applied to objects of type money or money2.
<<#(min (new money 1.3) (new money 3.1))#value;;
- : float = 1.3
#(min (new money2 5.0) (new money2 3.14))#value;;
- : float = 3.14
>>
More examples of binary methods can be found in sections 5.2.1 and 5.2.3.
Notice the use of functional update for method times. Writing new money2 (k
*. repr) instead of {< repr = k *. repr >} would not behave well with
inheritance: in a subclass money3 of money2 the times method would return an
object of class money2 but not of class money3 as would be expected.
The class money could naturally carry another binary method. Here is a direct
definition:
<<#class money x =
# object (self : 'a)
# val repr = x
# method value = repr
# method print = print_float repr
# method times k = {< repr = k *. x >}
# method leq (p : 'a) = repr <= p#value
# method plus (p : 'a) = {< repr = x +. p#value >}
# end;;
class money :
float ->
object ('a)
val repr : float
method leq : 'a -> bool
method plus : 'a -> 'a
method print : unit
method times : float -> 'a
method value : float
end
>>
3.15 Friends
*=*=*=*=*=*=*=
The above class money reveals a problem that often occurs with binary
methods. In order to interact with other objects of the same class, the
representation of money objects must be revealed, using a method such as value.
If we remove all binary methods (here plus and leq), the representation can
easily be hidden inside objects by removing the method value as well. However,
this is not possible as long as some binary requires access to the
representation on object of the same class but different from self.
<<#class safe_money x =
# object (self : 'a)
# val repr = x
# method print = print_float repr
# method times k = {< repr = k *. x >}
# end;;
class safe_money :
float ->
object ('a)
val repr : float
method print : unit
method times : float -> 'a
end
>>
Here, the representation of the object is known only to a particular object.
To make it available to other objects of the same class, we are forced to make
it available to the whole world. However we can easily restrict the visibility
of the representation using the module system.
<<#module type MONEY =
# sig
# type t
# class c : float ->
# object ('a)
# val repr : t
# method value : t
# method print : unit
# method times : float -> 'a
# method leq : 'a -> bool
# method plus : 'a -> 'a
# end
# end;;
#module Euro : MONEY =
# struct
# type t = float
# class c x =
# object (self : 'a)
# val repr = x
# method value = repr
# method print = print_float repr
# method times k = {< repr = k *. x >}
# method leq (p : 'a) = repr <= p#value
# method plus (p : 'a) = {< repr = x +. p#value >}
# end
# end;;
>>
Another example of friend functions may be found in section 5.2.3. These
examples occur when a group of objects (here objects of the same class) and
functions should see each others internal representation, while their
representation should be hidden from the outside. The solution is always to
define all friends in the same module, give access to the representation and
use a signature constraint to make the representation abstract outside of the
module.
Chapter 4 The module system
*******************************
This chapter introduces the module system of Objective Caml.
4.1 Structures
*=*=*=*=*=*=*=*=
A primary motivation for modules is to package together related definitions
(such as the definitions of a data type and associated operations over that
type) and enforce a consistent naming scheme for these definitions. This avoids
running out of names or accidentally confusing names. Such a package is called
a structure and is introduced by the struct...end construct, which contains an
arbitrary sequence of definitions. The structure is usually given a name with
the module binding. Here is for instance a structure packaging together a type
of priority queues and their operations:
<<#module PrioQueue =
# struct
# type priority = int
# type 'a queue = Empty | Node of priority * 'a * 'a queue * 'a queue
# let empty = Empty
# let rec insert queue prio elt =
# match queue with
# Empty -> Node(prio, elt, Empty, Empty)
# | Node(p, e, left, right) ->
# if prio <= p
# then Node(prio, elt, insert right p e, left)
# else Node(p, e, insert right prio elt, left)
# exception Queue_is_empty
# let rec remove_top = function
# Empty -> raise Queue_is_empty
# | Node(prio, elt, left, Empty) -> left
# | Node(prio, elt, Empty, right) -> right
# | Node(prio, elt, (Node(lprio, lelt, _, _) as left),
# (Node(rprio, relt, _, _) as right)) ->
# if lprio <= rprio
# then Node(lprio, lelt, remove_top left, right)
# else Node(rprio, relt, left, remove_top right)
# let extract = function
# Empty -> raise Queue_is_empty
# | Node(prio, elt, _, _) as queue -> (prio, elt, remove_top queue)
# end;;
module PrioQueue :
sig
type priority = int
and 'a queue = Empty | Node of priority * 'a * 'a queue * 'a queue
val empty : 'a queue
val insert : 'a queue -> priority -> 'a -> 'a queue
exception Queue_is_empty
val remove_top : 'a queue -> 'a queue
val extract : 'a queue -> priority * 'a * 'a queue
end
>>
Outside the structure, its components can be referred to using the ``dot
notation'', that is, identifiers qualified by a structure name. For instance,
PrioQueue.insert in a value context is the function insert defined inside the
structure PrioQueue. Similarly, PrioQueue.queue in a type context is the type
queue defined in PrioQueue.
<<#PrioQueue.insert PrioQueue.empty 1 "hello";;
- : string PrioQueue.queue =
PrioQueue.Node (1, "hello", PrioQueue.Empty, PrioQueue.Empty)
>>
4.2 Signatures
*=*=*=*=*=*=*=*=
Signatures are interfaces for structures. A signature specifies which
components of a structure are accessible from the outside, and with which type.
It can be used to hide some components of a structure (e.g. local function
definitions) or export some components with a restricted type. For instance,
the signature below specifies the three priority queue operations empty, insert
and extract, but not the auxiliary function remove_top. Similarly, it makes the
queue type abstract (by not providing its actual representation as a concrete
type).
<<#module type PRIOQUEUE =
# sig
# type priority = int (* still concrete *)
# type 'a queue (* now abstract *)
# val empty : 'a queue
# val insert : 'a queue -> int -> 'a -> 'a queue
# val extract : 'a queue -> int * 'a * 'a queue
# exception Queue_is_empty
# end;;
module type PRIOQUEUE =
sig
type priority = int
and 'a queue
val empty : 'a queue
val insert : 'a queue -> int -> 'a -> 'a queue
val extract : 'a queue -> int * 'a * 'a queue
exception Queue_is_empty
end
>>
Restricting the PrioQueue structure by this signature results in another
view of the PrioQueue structure where the remove_top function is not accessible
and the actual representation of priority queues is hidden:
<<#module AbstractPrioQueue = (PrioQueue : PRIOQUEUE);;
module AbstractPrioQueue : PRIOQUEUE
#AbstractPrioQueue.remove_top;;
Unbound value AbstractPrioQueue.remove_top
#AbstractPrioQueue.insert AbstractPrioQueue.empty 1 "hello";;
- : string AbstractPrioQueue.queue = <abstr>
>>
The restriction can also be performed during the definition of the
structure, as in
<<
module PrioQueue = (struct ... end : PRIOQUEUE);;
>>
An alternate syntax is provided for the above:
<<
module PrioQueue : PRIOQUEUE = struct ... end;;
>>
4.3 Functors
*=*=*=*=*=*=*=
Functors are ``functions'' from structures to structures. They are used to
express parameterized structures: a structure A parameterized by a structure B
is simply a functor F with a formal parameter B (along with the expected
signature for B) which returns the actual structure A itself. The functor F can
then be applied to one or several implementations B_1 ...B_n of B, yielding the
corresponding structures A_1 ...A_n.
For instance, here is a structure implementing sets as sorted lists,
parameterized by a structure providing the type of the set elements and an
ordering function over this type (used to keep the sets sorted):
<<#type comparison = Less | Equal | Greater;;
type comparison = Less | Equal | Greater
#module type ORDERED_TYPE =
# sig
# type t
# val compare: t -> t -> comparison
# end;;
module type ORDERED_TYPE = sig type t val compare : t -> t -> comparison end
#module Set =
# functor (Elt: ORDERED_TYPE) ->
# struct
# type element = Elt.t
# type set = element list
# let empty = []
# let rec add x s =
# match s with
# [] -> [x]
# | hd::tl ->
# match Elt.compare x hd with
# Equal -> s (* x is already in s *)
# | Less -> x :: s (* x is smaller than all elements of s *)
# | Greater -> hd :: add x tl
# let rec member x s =
# match s with
# [] -> false
# | hd::tl ->
# match Elt.compare x hd with
# Equal -> true (* x belongs to s *)
# | Less -> false (* x is smaller than all elements of s *)
# | Greater -> member x tl
# end;;
module Set :
functor (Elt : ORDERED_TYPE) ->
sig
type element = Elt.t
and set = element list
val empty : 'a list
val add : Elt.t -> Elt.t list -> Elt.t list
val member : Elt.t -> Elt.t list -> bool
end
>>
By applying the Set functor to a structure implementing an ordered type, we
obtain set operations for this type:
<<#module OrderedString =
# struct
# type t = string
# let compare x y = if x = y then Equal else if x < y then Less else
Greater
# end;;
module OrderedString :
sig type t = string val compare : 'a -> 'a -> comparison end
#module StringSet = Set(OrderedString);;
module StringSet :
sig
type element = OrderedString.t
and set = element list
val empty : 'a list
val add : OrderedString.t -> OrderedString.t list -> OrderedString.t list
val member : OrderedString.t -> OrderedString.t list -> bool
end
#StringSet.member "bar" (StringSet.add "foo" StringSet.empty);;
- : bool = false
>>
4.4 Functors and type abstraction
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
As in the PrioQueue example, it would be good style to hide the actual
implementation of the type set, so that users of the structure will not rely on
sets being lists, and we can switch later to another, more efficient
representation of sets without breaking their code. This can be achieved by
restricting Set by a suitable functor signature:
<<#module type SETFUNCTOR =
# functor (Elt: ORDERED_TYPE) ->
# sig
# type element = Elt.t (* concrete *)
# type set (* abstract *)
# val empty : set
# val add : element -> set -> set
# val member : element -> set -> bool
# end;;
module type SETFUNCTOR =
functor (Elt : ORDERED_TYPE) ->
sig
type element = Elt.t
and set
val empty : set
val add : element -> set -> set
val member : element -> set -> bool
end
#module AbstractSet = (Set : SETFUNCTOR);;
module AbstractSet : SETFUNCTOR
#module AbstractStringSet = AbstractSet(OrderedString);;
module AbstractStringSet :
sig
type element = OrderedString.t
and set = AbstractSet(OrderedString).set
val empty : set
val add : element -> set -> set
val member : element -> set -> bool
end
#AbstractStringSet.add "gee" AbstractStringSet.empty;;
- : AbstractStringSet.set = <abstr>
>>
In an attempt to write the type constraint above more elegantly, one may wish
to name the signature of the structure returned by the functor, then use that
signature in the constraint:
<<#module type SET =
# sig
# type element
# type set
# val empty : set
# val add : element -> set -> set
# val member : element -> set -> bool
# end;;
module type SET =
sig
type element
and set
val empty : set
val add : element -> set -> set
val member : element -> set -> bool
end
#module WrongSet = (Set : functor(Elt: ORDERED_TYPE) -> SET);;
module WrongSet : functor (Elt : ORDERED_TYPE) -> SET
#module WrongStringSet = WrongSet(OrderedString);;
module WrongStringSet :
sig
type element = WrongSet(OrderedString).element
and set = WrongSet(OrderedString).set
val empty : set
val add : element -> set -> set
val member : element -> set -> bool
end
#WrongStringSet.add "gee" WrongStringSet.empty;;
This expression has type string but is here used with type
WrongStringSet.element = WrongSet(OrderedString).element
>>
The problem here is that SET specifies the type element abstractly, so that
the type equality between element in the result of the functor and t in its
argument is forgotten. Consequently, WrongStringSet.element is not the same
type as string, and the operations of WrongStringSet cannot be applied to
strings. As demonstrated above, it is important that the type element in the
signature SET be declared equal to Elt.t; unfortunately, this is impossible
above since SET is defined in a context where Elt does not exist. To overcome
this difficulty, Objective Caml provides a with type construct over signatures
that allows to enrich a signature with extra type equalities:
<<#module AbstractSet =
# (Set : functor(Elt: ORDERED_TYPE) -> (SET with type element = Elt.t));;
module AbstractSet :
functor (Elt : ORDERED_TYPE) ->
sig
type element = Elt.t
and set
val empty : set
val add : element -> set -> set
val member : element -> set -> bool
end
>>
As in the case of simple structures, an alternate syntax is provided for
defining functors and restricting their result:
<<
module AbstractSet(Elt: ORDERED_TYPE) : (SET with type element = Elt.t) =
struct ... end;;
>>
Abstracting a type component in a functor result is a powerful technique that
provides a high degree of type safety, as we now illustrate. Consider an
ordering over character strings that is different from the standard ordering
implemented in the OrderedString structure. For instance, we compare strings
without distinguishing upper and lower case.
<<#module NoCaseString =
# struct
# type t = string
# let compare s1 s2 =
# OrderedString.compare (String.lowercase s1) (String.lowercase s2)
# end;;
module NoCaseString :
sig type t = string val compare : string -> string -> comparison end
#module NoCaseStringSet = AbstractSet(NoCaseString);;
module NoCaseStringSet :
sig
type element = NoCaseString.t
and set = AbstractSet(NoCaseString).set
val empty : set
val add : element -> set -> set
val member : element -> set -> bool
end
#NoCaseStringSet.add "FOO" AbstractStringSet.empty;;
This expression has type
AbstractStringSet.set = AbstractSet(OrderedString).set
but is here used with type
NoCaseStringSet.set = AbstractSet(NoCaseString).set
>>
Notice that the two types AbstractStringSet.set and NoCaseStringSet.set are
not compatible, and values of these two types do not match. This is the correct
behavior: even though both set types contain elements of the same type
(strings), both are built upon different orderings of that type, and different
invariants need to be maintained by the operations (being strictly increasing
for the standard ordering and for the case-insensitive ordering). Applying
operations from AbstractStringSet to values of type NoCaseStringSet.set could
give incorrect results, or build lists that violate the invariants of
NoCaseStringSet.
4.5 Modules and separate compilation
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
All examples of modules so far have been given in the context of the
interactive system. However, modules are most useful for large, batch-compiled
programs. For these programs, it is a practical necessity to split the source
into several files, called compilation units, that can be compiled separately,
thus minimizing recompilation after changes.
In Objective Caml, compilation units are special cases of structures and
signatures, and the relationship between the units can be explained easily in
terms of the module system. A compilation unit a comprises two files:
- the implementation file a.ml, which contains a sequence of definitions,
analogous to the inside of a struct...end construct;
- the interface file a.mli, which contains a sequence of specifications,
analogous to the inside of a sig...end construct.
Both files define a structure named A (same name as the base name a of the
two files, with the first letter capitalized), as if the following definition
was entered at top-level:
<<
module A: sig (* contents of file a.mli *) end
= struct (* contents of file a.ml *) end;;
>>
The files defining the compilation units can be compiled separately using
the ocaml -c command (the -c option means ``compile only, do not try to
link''); this produces compiled interface files (with extension .cmi) and
compiled object code files (with extension .cmo). When all units have been
compiled, their .cmo files are linked together using the ocaml command. For
instance, the following commands compile and link a program composed of two
compilation units aux and main:
<<
$ ocamlc -c aux.mli # produces aux.cmi
$ ocamlc -c aux.ml # produces aux.cmo
$ ocamlc -c main.mli # produces main.cmi
$ ocamlc -c main.ml # produces main.cmo
$ ocamlc -o theprogram aux.cmo main.cmo
>>
The program behaves exactly as if the following phrases were entered at
top-level:
<<
module Aux: sig (* contents of aux.mli *) end
= struct (* contents of aux.ml *) end;;
module Main: sig (* contents of main.mli *) end
= struct (* contents of main.ml *) end;;
>>
In particular, Main can refer to Aux: the definitions and declarations
contained in main.ml and main.mli can refer to definition in aux.ml, using the
Aux.ident notation, provided these definitions are exported in aux.mli.
The order in which the .cmo files are given to ocaml during the linking phase
determines the order in which the module definitions occur. Hence, in the
example above, Aux appears first and Main can refer to it, but Aux cannot refer
to Main.
Notice that only top-level structures can be mapped to separately-compiled
files, but not functors nor module types. However, all module-class objects can
appear as components of a structure, so the solution is to put the functor or
module type inside a structure, which can then be mapped to a file.
Chapter 5 Advanced examples with classes and modules
********************************************************
(Chapter written by Didier Rémy)
In this chapter, we show some larger examples using objects, classes and
modules. We review many of the object features simultaneously on the example of
a bank account. We show how modules taken from the standard library can be
expressed as classes. Lastly, we describe a programming pattern know of as
virtual types through the example of window managers.
5.1 Extended example: bank accounts
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
In this section, we illustrate most aspects of Object and inheritance by
refining, debugging, and specializing the following initial naive definition
of a simple bank account. (We reuse the module Euro defined at the end of
chapter 3.)
<<#let euro = new Euro.c;;
val euro : float -> Euro.c = <fun>
#let zero = euro 0.;;
val zero : Euro.c = <obj>
#let neg x = x#times (-1.);;
val neg : < times : float -> 'a; .. > -> 'a = <fun>
#class account =
# object
# val mutable balance = zero
# method balance = balance
# method deposit x = balance <- balance # plus x
# method withdraw x =
# if x#leq balance then (balance <- balance # plus (neg x); x) else zero
# end;;
class account :
object
val mutable balance : Euro.c
method balance : Euro.c
method deposit : Euro.c -> unit
method withdraw : Euro.c -> Euro.c
end
#let c = new account in c # deposit (euro 100.); c # withdraw (euro 50.);;
- : Euro.c = <obj>
>>
We now refine this definition with a method to compute interest.
<<#class account_with_interests =
# object (self)
# inherit account
# method private interest = self # deposit (self # balance # times 0.03)
# end;;
class account_with_interests :
object
val mutable balance : Euro.c
method balance : Euro.c
method deposit : Euro.c -> unit
method private interest : unit
method withdraw : Euro.c -> Euro.c
end
>>
We make the method interest private, since clearly it should not be called
freely from the outside. Here, it is only made accessible to subclasses that
will manage monthly or yearly updates of the account.
We should soon fix a bug in the current definition: the deposit method can be
used for withdrawing money by depositing negative amounts. We can fix this
directly:
<<#class safe_account =
# object
# inherit account
# method deposit x = if zero#leq x then balance <- balance#plus x
# end;;
class safe_account :
object
val mutable balance : Euro.c
method balance : Euro.c
method deposit : Euro.c -> unit
method withdraw : Euro.c -> Euro.c
end
>>
However, the bug might be fixed more safely by the following definition:
<<#class safe_account =
# object
# inherit account as unsafe
# method deposit x =
# if zero#leq x then unsafe # deposit x
# else raise (Invalid_argument "deposit")
# end;;
class safe_account :
object
val mutable balance : Euro.c
method balance : Euro.c
method deposit : Euro.c -> unit
method withdraw : Euro.c -> Euro.c
end
>>
In particular, this does not require the knowledge of the implementation of
the method deposit.
To keep trace of operations, we extend the class with a mutable field history
and a private method trace to add an operation in the log. Then each method to
be traced is redefined.
<<#type 'a operation = Deposit of 'a | Retrieval of 'a;;
type 'a operation = Deposit of 'a | Retrieval of 'a
#class account_with_history =
# object (self)
# inherit safe_account as super
# val mutable history = []
# method private trace x = history <- x :: history
# method deposit x = self#trace (Deposit x); super#deposit x
# method withdraw x = self#trace (Retrieval x); super#withdraw x
# method history = List.rev history
# end;;
class account_with_history :
object
val mutable balance : Euro.c
val mutable history : Euro.c operation list
method balance : Euro.c
method deposit : Euro.c -> unit
method history : Euro.c operation list
method private trace : Euro.c operation -> unit
method withdraw : Euro.c -> Euro.c
end
>>
One may wish to open an account and simultaneously deposit some initial
amount. Although the initial implementation did not address this requirement,
it can be achieved by using an initializer.
<<#class account_with_deposit x =
# object
# inherit account_with_history
# initializer balance <- x
# end;;
class account_with_deposit :
Euro.c ->
object
val mutable balance : Euro.c
val mutable history : Euro.c operation list
method balance : Euro.c
method deposit : Euro.c -> unit
method history : Euro.c operation list
method private trace : Euro.c operation -> unit
method withdraw : Euro.c -> Euro.c
end
>>
A better alternative is:
<<#class account_with_deposit x =
# object (self)
# inherit account_with_history
# initializer self#deposit x
# end;;
class account_with_deposit :
Euro.c ->
object
val mutable balance : Euro.c
val mutable history : Euro.c operation list
method balance : Euro.c
method deposit : Euro.c -> unit
method history : Euro.c operation list
method private trace : Euro.c operation -> unit
method withdraw : Euro.c -> Euro.c
end
>>
Indeed, the latter is safer since the call to deposit will automatically
benefit from safety checks and from the trace. Let's test it:
<<#let ccp = new account_with_deposit (euro 100.) in
#let balance = ccp#withdraw (euro 50.) in
#ccp#history;;
- : Euro.c operation list = [Deposit <obj>; Retrieval <obj>]
>>
Closing an account can be done with the following polymorphic function:
<<#let close c = c#withdraw (c#balance);;
val close : < balance : 'a; withdraw : 'a -> 'b; .. > -> 'b = <fun>
>>
Of course, this applies to all sorts of accounts.
Finally, we gather several versions of the account into a module Account
abstracted over some currency.
<<#let today () = (01,01,2000) (* an approximation *)
#module Account (M:MONEY) =
# struct
# type m = M.c
# let m = new M.c
# let zero = m 0.
#
# class bank =
# object (self)
# val mutable balance = zero
# method balance = balance
# val mutable history = []
# method private trace x = history <- x::history
# method deposit x =
# self#trace (Deposit x);
# if zero#leq x then balance <- balance # plus x
# else raise (Invalid_argument "deposit")
# method withdraw x =
# if x#leq balance then
# (balance <- balance # plus (neg x); self#trace (Retrieval x); x)
# else zero
# method history = List.rev history
# end
#
# class type client_view =
# object
# method deposit : m -> unit
# method history : m operation list
# method withdraw : m -> m
# method balance : m
# end
#
# class virtual check_client x =
# let y = if (m 100.)#leq x then x
# else raise (Failure "Insufficient initial deposit") in
# object (self) initializer self#deposit y end
#
# module Client (B : sig class bank : client_view end) =
# struct
# class account x : client_view =
# object
# inherit B.bank
# inherit check_client x
# end
#
# let discount x =
# let c = new account x in
# if today() < (1998,10,30) then c # deposit (m 100.); c
# end
# end;;
>>
This shows the use of modules to group several class definitions that can in
fact be thought of as a single unit. This unit would be provided by a bank for
both internal and external uses. This is implemented as a functor that
abstracts over the currency so that the same code can be used to provide
accounts in different currencies.
The class bank is the real implementation of the bank account (it could have
been inlined). This is the one that will be used for further extensions,
refinements, etc. Conversely, the client will only be given the client view.
<<#module Euro_account = Account(Euro);;
#module Client = Euro_account.Client (Euro_account);;
#new Client.account (new Euro.c 100.);;
>>
Hence, the clients do not have direct access to the balance, nor the history
of their own accounts. Their only way to change their balance is to deposit or
withdraw money. It is important to give the clients a class and not just the
ability to create accounts (such as the promotional discount account), so that
they can personalize their account. For instance, a client may refine the
deposit and withdraw methods so as to do his own financial bookkeeping,
automatically. On the other hand, the function discount is given as such, with
no possibility for further personalization.
It is important that to provide the client's view as a functor Client so that
client accounts can still be build after a possible specialization of the bank.
The functor Client may remain unchanged and be passed the new definition to
initialize a client's view of the extended account.
<<#module Investment_account (M : MONEY) =
# struct
# type m = M.c
# module A = Account(M)
#
# class bank =
# object
# inherit A.bank as super
# method deposit x =
# if (new M.c 1000.)#leq x then
# print_string "Would you like to invest?";
# super#deposit x
# end
#
# module Client = A.Client
# end;;
>>
The functor Client may also be redefined when some new features of the
account can be given to the client.
<<#module Internet_account (M : MONEY) =
# struct
# type m = M.c
# module A = Account(M)
# class bank =
# object
# inherit A.bank
# method mail s = print_string s
# end
#
# class type client_view =
# object
# method deposit : m -> unit
# method history : m operation list
# method withdraw : m -> m
# method balance : m
# method mail : string -> unit
# end
#
# module Client (B : sig class bank : client_view end) =
# struct
# class account x : client_view =
# object
# inherit B.bank
# inherit A.check_client x
# end
# end
# end;;
>>
5.2 Simple modules as classes
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
One may wonder whether it is possible to treat primitive types such as
integers and strings as objects. Although this is usually uninteresting for
integers or strings, there may be some situations where this is desirable. The
class money above is such an example. We show here how to do it for strings.
5.2.1 Strings
===============
A naive definition of strings as objects could be:
<<#class ostring s =
# object
# method get n = String.get n
# method set n c = String.set n c
# method print = print_string s
# method copy = new ostring (String.copy s)
# end;;
class ostring :
string ->
object
method copy : ostring
method get : string -> int -> char
method print : unit
method set : string -> int -> char -> unit
end
>>
However, the method copy returns an object of the class string, and not an
objet of the current class. Hence, if the class is further extended, the method
copy will only return an object of the parent class.
<<#class sub_string s =
# object
# inherit ostring s
# method sub start len = new sub_string (String.sub s start len)
# end;;
class sub_string :
string ->
object
method copy : ostring
method get : string -> int -> char
method print : unit
method set : string -> int -> char -> unit
method sub : int -> int -> sub_string
end
>>
As seen in section 3.14, the solution is to use functional update instead.
We need to create an instance variable containing the representation s of the
string.
<<#class better_string s =
# object
# val repr = s
# method get n = String.get n
# method set n c = String.set n c
# method print = print_string repr
# method copy = {< repr = String.copy repr >}
# method sub start len = {< repr = String.sub s start len >}
# end;;
class better_string :
string ->
object ('a)
val repr : string
method copy : 'a
method get : string -> int -> char
method print : unit
method set : string -> int -> char -> unit
method sub : int -> int -> 'a
end
>>
As shown in the inferred type, the methods copy and sub now return objects
of the same type as the one of the class.
Another difficulty is the implementation of the method concat. In order to
concatenate a string with another string of the same class, one must be able
to access the instance variable externally. Thus, a method repr returning s
must be defined. Here is the correct definition of strings:
<<#class ostring s =
# object (self : 'mytype)
# val repr = s
# method repr = repr
# method get n = String.get n
# method set n c = String.set n c
# method print = print_string repr
# method copy = {< repr = String.copy repr >}
# method sub start len = {< repr = String.sub s start len >}
# method concat (t : 'mytype) = {< repr = repr ^ t#repr >}
# end;;
class ostring :
string ->
object ('a)
val repr : string
method concat : 'a -> 'a
method copy : 'a
method get : string -> int -> char
method print : unit
method repr : string
method set : string -> int -> char -> unit
method sub : int -> int -> 'a
end
>>
Another constructor of the class string can be defined to return an
uninitialized string of a given length:
<<#class cstring n = ostring (String.create n);;
class cstring : int -> ostring
>>
Here, exposing the representation of strings is probably harmless. We do
could also hide the representation of strings as we hid the currency in the
class money of section 3.15.
Stacks
-------
There is sometimes an alternative between using modules or classes for
parametric data types. Indeed, there are situations when the two approaches
are quite similar. For instance, a stack can be straightforwardly implemented
as a class:
<<#exception Empty;;
exception Empty
#class ['a] stack =
# object
# val mutable l = ([] : 'a list)
# method push x = l <- x::l
# method pop = match l with [] -> raise Empty | a::l' -> l <- l'; a
# method clear = l <- []
# method length = List.length l
# end;;
class ['a] stack :
object
val mutable l : 'a list
method clear : unit
method length : int
method pop : 'a
method push : 'a -> unit
end
>>
However, writing a method for iterating over a stack is more problematic. A
method fold would have type ('b -> 'a -> 'b) -> 'b -> 'b. Here 'a is the
parameter of the stack. The parameter 'b is not related to the class 'a stack
but to the argument that will be passed to the method fold. The intuition is
that method fold should be polymorphic, i.e. of type All ('a) ('b -> 'a -> 'b)
-> 'b -> 'b, which is not currently possible. One possibility would be to make
'b an extra parameter of class stack:
<<#class ['a, 'b] stack2 =
# object
# inherit ['a] stack
# method fold f (x : 'b) = List.fold_left f x l
# end;;
class ['a, 'b] stack2 :
object
val mutable l : 'a list
method clear : unit
method fold : ('b -> 'a -> 'b) -> 'b -> 'b
method length : int
method pop : 'a
method push : 'a -> unit
end
>>
However, the method fold of a given object can only be applied to functions
that all have the same type:
<<#let s = new stack2;;
val s : ('_a, '_b) stack2 = <obj>
#s#fold (+) 0;;
- : int = 0
#s;;
- : (int, int) stack2 = <obj>
>>
The best solution would be to make method fold polymorphic. However, OCaml
does not currently allow methods to be polymorphic. Thus, the current solution
is to leave the function fold outside of the class.
<<#class ['a] stack3 =
# object
# inherit ['a] stack
# method iter f = List.iter (f : 'a -> unit) l
# end;;
class ['a] stack3 :
object
val mutable l : 'a list
method clear : unit
method iter : ('a -> unit) -> unit
method length : int
method pop : 'a
method push : 'a -> unit
end
#let stack_fold (s : 'a #stack3) f x =
# let accu = ref x in
# s#iter (fun e -> accu := f !accu e);
# !accu;;
val stack_fold : 'a #stack3 -> ('b -> 'a -> 'b) -> 'b -> 'b = <fun>
>>
5.2.2 Hashtbl
===============
A simplified version of object-oriented hash tables should have the following
class type.
<<#class type ['a, 'b] hash_table =
# object
# method find : 'a -> 'b
# method add : 'a -> 'b -> unit
# end;;
class type ['a, 'b] hash_table =
object method add : 'a -> 'b -> unit method find : 'a -> 'b end
>>
A simple implementation, which is quite reasonable for small hastables is to
use an association list:
<<#class ['a, 'b] small_hashtbl : ['a, 'b] hash_table =
# object
# val mutable table = []
# method find key = List.assoc key table
# method add key valeur = table <- (key, valeur) :: table
# end;;
class ['a, 'b] small_hashtbl : ['a, 'b] hash_table
>>
A better implementation, and one that scales up better, is to use a true
hash tables... whose elements are small hash tables!
<<#class ['a, 'b] hashtbl size : ['a, 'b] hash_table =
# object (self)
# val table = Array.init size (fun i -> new small_hashtbl)
# method private hash key =
# (Hashtbl.hash key) mod (Array.length table)
# method find key = table.(self#hash key) # find key
# method add key = table.(self#hash key) # add key
# end;;
class ['a, 'b] hashtbl : int -> ['a, 'b] hash_table
>>
5.2.3 Sets
============
Implementing sets leads to another difficulty. Indeed, the method union needs
to be able to access the internal representation of another object of the same
class.
This is another instance of friend functions as seen in section 3.15. Indeed,
this is the same mechanism used in the module Set in the absence of objects.
In the object-oriented version of sets, we only need to add an additional
method tag to return the representation of a set. Since sets are parametric in
the type of elements, the method tag has a parametric type 'a tag, concrete
within the module definition but abstract in its signature. From outside, it
will then be guaranteed that two objects with a method tag of the same type
will share the same representation.
<<#module type SET =
# sig
# type 'a tag
# class ['a] c :
# object ('b)
# method is_empty : bool
# method mem : 'a -> bool
# method add : 'a -> 'b
# method union : 'b -> 'b
# method iter : ('a -> unit) -> unit
# method tag : 'a tag
# end
# end;;
#module Set : SET =
# struct
# let rec merge l1 l2 =
# match l1 with
# [] -> l2
# | h1 :: t1 ->
# match l2 with
# [] -> l1
# | h2 :: t2 ->
# if h1 < h2 then h1 :: merge t1 l2
# else if h1 > h2 then h2 :: merge l1 t2
# else merge t1 l2
# type 'a tag = 'a list
# class ['a] c =
# object (_ : 'b)
# val repr = ([] : 'a list)
# method is_empty = (repr = [])
# method mem x = List.exists ((=) x) repr
# method add x = {< repr = merge [x] repr >}
# method union (s : 'b) = {< repr = merge repr s#tag >}
# method iter (f : 'a -> unit) = List.iter f repr
# method tag = repr
# end
# end;;
>>
5.3 The subject/observer pattern
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
The following example, known as the subject/observer pattern, is often
presented in the literature as a difficult inheritance problem with
inter-connected classes. The general pattern amounts to the definition a pair
of two classes that recursively interact with one another.
The class observer has a distinguished method notify that requires two
arguments, a subject and an event to execute an action.
<<#class virtual ['subject, 'event] observer =
# object
# method virtual notify : 'subject -> 'event -> unit
# end;;
class virtual ['a, 'b] observer :
object method virtual notify : 'a -> 'b -> unit end
>>
The class subject remembers a list of observers in an instance variable, and
has a distinguished method notify_observers to broadcast the message notify to
all observers with a particular event e.
<<#class ['observer, 'event] subject =
# object (self)
# val mutable observers = ([]:'observer list)
# method add_observer obs = observers <- (obs :: observers)
# method notify_observers (e : 'event) =
# List.iter (fun x -> x#notify self e) observers
# end;;
class ['a, 'b] subject :
object ('c)
constraint 'a = < notify : 'c -> 'b -> unit; .. >
val mutable observers : 'a list
method add_observer : 'a -> unit
method notify_observers : 'b -> unit
end
>>
The difficulty usually relies in defining instances of the pattern above by
inheritance. This can be done in a natural and obvious manner in Ocaml, as
shown on the following example manipulating windows.
<<#type event = Raise | Resize | Move;;
type event = Raise | Resize | Move
#let string_of_event = function
# Raise -> "Raise" | Resize -> "Resize" | Move -> "Move";;
val string_of_event : event -> string = <fun>
#let count = ref 0;;
val count : int ref = {contents=0}
#class ['observer] window_subject =
# let id = count := succ !count; !count in
# object (self)
# inherit ['observer, event] subject
# val mutable position = 0
# method identity = id
# method move x = position <- position + x; self#notify_observers Move
# method draw = Printf.printf "{Position = %d}\n" position;
# end;;
class ['a] window_subject :
object ('b)
constraint 'a = < notify : 'b -> event -> unit; .. >
val mutable observers : 'a list
val mutable position : int
method add_observer : 'a -> unit
method draw : unit
method identity : int
method move : int -> unit
method notify_observers : event -> unit
end
#class ['subject] window_observer =
# object
# inherit ['subject, event] observer
# method notify s e = s#draw
# end;;
class ['a] window_observer :
object
constraint 'a = < draw : unit; .. >
method notify : 'a -> event -> unit
end
>>
Unsurprisingly the type of window is recursive.
<<#let window = new window_subject;;
val window : < notify : 'a -> event -> unit; _.. > window_subject as 'a =
<obj>
>>
However, the two classes of window_subject and window_observer are not
mutually recursive.
<<#let window_observer = new window_observer;;
val window_observer : < draw : unit; _.. > window_observer = <obj>
#window#add_observer window_observer;;
- : unit = ()
#window#move 1;;
{Position = 1}
- : unit = ()
>>
Classes window_observer and window_subject can still be extended by
inheritance. For instance, one may enrich the subject with new behaviors and
refined the behavior of the observer.
<<#class ['observer] richer_window_subject =
# object (self)
# inherit ['observer] window_subject
# val mutable size = 1
# method resize x = size <- size + x; self#notify_observers Resize
# val mutable top = false
# method raise = top <- true; self#notify_observers Raise
# method draw = Printf.printf "{Position = %d; Size = %d}\n" position
size;
# end;;
class ['a] richer_window_subject :
object ('b)
constraint 'a = < notify : 'b -> event -> unit; .. >
val mutable observers : 'a list
val mutable position : int
val mutable size : int
val mutable top : bool
method add_observer : 'a -> unit
method draw : unit
method identity : int
method move : int -> unit
method notify_observers : event -> unit
method raise : unit
method resize : int -> unit
end
#class ['subject] richer_window_observer =
# object
# inherit ['subject] window_observer as super
# method notify s e = if e <> Raise then s#raise; super#notify s e
# end;;
class ['a] richer_window_observer :
object
constraint 'a = < draw : unit; raise : unit; .. >
method notify : 'a -> event -> unit
end
>>
We can also create a different kind of observer:
<<#class ['subject] trace_observer =
# object
# inherit ['subject, event] observer
# method notify s e =
# Printf.printf
# "<Window %d <== %s>\n" s#identity (string_of_event e)
# end;;
class ['a] trace_observer :
object
constraint 'a = < identity : int; .. >
method notify : 'a -> event -> unit
end
>>
and attached several observers to the same object:
<<#let window = new richer_window_subject;;
val window :
< notify : 'a -> event -> unit; _.. > richer_window_subject as 'a = <obj>
#window#add_observer (new richer_window_observer);;
- : unit = ()
#window#add_observer (new trace_observer);;
- : unit = ()
#window#move 1; window#resize 2;;
<Window 2 <== Move>
<Window 2 <== Raise>
{Position = 1; Size = 1}
{Position = 1; Size = 1}
<Window 2 <== Resize>
<Window 2 <== Raise>
{Position = 1; Size = 3}
{Position = 1; Size = 3}
- : unit = ()
>>
Part: II
********
The Objective Caml language
****************************
Chapter 6 The Objective Caml language
*****************************************
Foreword
*=*=*=*=
This document is intended as a reference manual for the Objective Caml
language. It lists the language constructs, and gives their precise syntax and
informal semantics. It is by no means a tutorial introduction to the language:
there is not a single example. A good working knowledge of Caml is assumed.
No attempt has been made at mathematical rigor: words are employed with their
intuitive meaning, without further definition. As a consequence, the typing
rules have been left out, by lack of the mathematical framework required to
express them, while they are definitely part of a full formal definition of the
language.
Notations
=========
The syntax of the language is given in BNF-like notation. Terminal symbols
are set in typewriter font (like this). Non-terminal symbols are set in italic
font (like that). Square brackets [...] denote optional components. Curly
brackets {...} denotes zero, one or several repetitions of the enclosed
components. Curly bracket with a trailing plus sign {...}^+ denote one or
several repetitions of the enclosed components. Parentheses (...) denote
grouping.
6.1 Lexical conventions
*=*=*=*=*=*=*=*=*=*=*=*=*
Blanks
------
The following characters are considered as blanks: space, newline, horizontal
tabulation, carriage return, line feed and form feed. Blanks are ignored, but
they separate adjacent identifiers, literals and keywords that would otherwise
be confused as one single identifier, literal or keyword.
Comments
--------
Comments are introduced by the two characters (*, with no intervening blanks,
and terminated by the characters *), with no intervening blanks. Comments are
treated as blank characters. Comments do not occur inside string or character
literals. Nested comments are handled correctly.
Identifiers
-----------
ident ::= (letter|_) { letter|0...9|_|' }
letter ::= A ... Z | a ... z
Identifiers are sequences of letters, digits, _ (the underscore character),
and ' (the single quote), starting with a letter or an underscore. Letters
contain at least the 52 lowercase and uppercase letters from the ASCII set. The
current implementation (except on MacOS) also recognizes as letters all
accented characters from the ISO 8859-1 (``ISO Latin 1'') set. All characters
in an identifier are meaningful. The current implementation places no limits on
the number of characters of an identifier.
Integer literals
----------------
+
integer-literal ::= [-] { 0...9 }
+
| [-] (0x|0X) { 0...9|A...F|a...f }
+
| [-] (0o|0O) { 0...7 }
+
| [-] (0b|0B) { 0...1 }
An integer literal is a sequence of one or more digits, optionally preceded
by a minus sign. By default, integer literals are in decimal (radix 10). The
following prefixes select a different radix:
-------------------------------
|Prefix| Radix |
-------------------------------
|0x, 0X|hexadecimal (radix 16)|
|0o, 0O|octal (radix 8) |
|0b, 0B|binary (radix 2) |
-------------------------------
(The initial 0 is the digit zero; the O for octal is the letter O.) The
interpretation of integer literals that fall outside the range of representable
integer values is undefined.
Floating-point literals
-----------------------
+ +
float-literal ::= [-] { 0...9 } [. { 0...9 }] [(e|E) [+|-] { 0...9 } ]
Floating-point decimals consist in an integer part, a decimal part and an
exponent part. The integer part is a sequence of one or more digits, optionally
preceded by a minus sign. The decimal part is a decimal point followed by zero,
one or more digits. The exponent part is the character e or E followed by an
optional + or - sign, followed by one or more digits. The decimal part or the
exponent part can be omitted, but not both to avoid ambiguity with integer
literals. The interpretation of floating-point literals that fall outside the
range of representable floating-point values is undefined.
Character literals
------------------
char-literal ::= ' regular-char '
| ' \ (\ | ' | n | t | b | r) '
| ' \ (0...9) (0...9) (0...9) '
Character literals are delimited by ' (single quote) characters. The two
single quotes enclose either one character different from ' and \, or one of
the escape sequences below:
-------------------------------------------------------
|Sequence| Character denoted |
-------------------------------------------------------
|\\ |backslash (\) |
|\' |single quote (') |
|\n |linefeed (LF) |
|\r |return (CR) |
|\t |horizontal tabulation (TAB) |
|\b |backspace (BS) |
|\ddd |the character with ASCII code ddd in decimal|
-------------------------------------------------------
String literals
---------------
string-literal ::= " { string-character } "
string-character ::= regular-char
| \ (\ | " | n | t | b | r)
| \ (0...9) (0...9) (0...9)
String literals are delimited by " (double quote) characters. The two double
quotes enclose a sequence of either characters different from " and \, or
escape sequences from the table below:
-------------------------------------------------------
|Sequence| Character denoted |
-------------------------------------------------------
|\\ |backslash (\) |
|\" |double quote (") |
|\n |linefeed (LF) |
|\r |return (CR) |
|\t |horizontal tabulation (TAB) |
|\b |backspace (BS) |
|\ddd |the character with ASCII code ddd in decimal|
-------------------------------------------------------
To allow splitting long string literals across lines, the sequence \newline
blanks (a \ at end-of-line followed by any number of blanks at the beginning of
the next line) is ignored inside string literals.
The current implementation places no restrictions on the length of string
literals.
Naming labels
-------------
To avoid ambiguities, naming labels cannot just be defined syntactically as
the sequence of the three tokens ~, ident and :, and have to be defined at the
lexical level.
label ::= ~ (a ... z) { letter|0...9|_|' } :
optlabel ::= ? (a ... z) { letter|0...9|_|' } :
Naming labels come in two flavours: label for normal arguments and optlabel
for optional ones. They are simply distinguished by their first character,
either ~ or ?.
Prefix and infix symbols
------------------------
infix-symbol ::= (= | < | > | @ | ^ | | | & | + | - | * | / | $ | %) {
operator-char }
prefix-symbol ::= (! | ? | ~) { operator-char }
operator-char ::= ! | $ | % | & | * | + | - | . | / | : | < | = | > | ? |
@ | ^ | | | ~
Sequences of ``operator characters'', such as <=> or !!, are read as a single
token from the infix-symbol or prefix-symbol class. These symbols are parsed as
prefix and infix operators inside expressions, but otherwise behave much as
identifiers.
Keywords
--------
The identifiers below are reserved as keywords, and cannot be employed
otherwise:
<<
and as assert asr begin class
closed constraint do done downto else
end exception external false for fun
function functor if in include inherit
land lazy let lor lsl lsr
lxor match method mod module mutable
new of open or parser private
rec sig struct then to true
try type val virtual when while
with
>>
The following character sequences are also keywords:
<<
# & ' ( ) * , -> ?
?? . .. .( .[ : :: := ;
;; <- = [ [| [< {< ] |]
>] >} _ ` { | } ~
>>
Ambiguities
-----------
Lexical ambiguities are resolved according to the ``longest match'' rule:
when a character sequence can be decomposed into two tokens in several
different ways, the decomposition retained is the one with the longest first
token.
Line number directives
----------------------
+
linenum-directive ::= # {0 ... 9}
+
| # {0 ... 9} " { string-character } "
Preprocessors that generate Caml source code can insert line number
directives in their output so that error messages produced by the compiler
contain line numbers and file names referring to the source file before
preprocessing, instead of after preprocessing. A line number directive is
composed of a # (sharp sign), followed by a positive integer (the source line
number), optionally followed by a character string (the source file name). Line
number directives are treated as blank characters during lexical analysis.
6.2 Values
*=*=*=*=*=*=
This section describes the kinds of values that are manipulated by Caml Light
programs.
6.2.1 Base values
===================
Integer numbers
---------------
Integer values are integer numbers from -2^30 to 2^30-1, that is -1073741824
to 1073741823. The implementation may support a wider range of integer values:
on 64-bit platforms, the current implementation supports integers ranging from
-2^62 to 2^62-1.
Floating-point numbers
----------------------
Floating-point values are numbers in floating-point representation. The
current implementation uses double-precision floating-point numbers conforming
to the IEEE 754 standard, with 53 bits of mantissa and an exponent ranging from
-1022 to 1023.
Characters
----------
Character values are represented as 8-bit integers between 0 and 255.
Character codes between 0 and 127 are interpreted following the ASCII standard.
The current implementation interprets character codes between 128 and 255
following the ISO 8859-1 standard.
Character strings
-----------------
String values are finite sequences of characters. The current implementation
supports strings containing up to 2^24 - 6 characters (16777210 characters).
6.2.2 Tuples
==============
Tuples of values are written (v_1, ..., v_n), standing for the n-tuple of
values v_1 to v_n. The current implementation supports tuple of up to 2^22 - 1
elements (4194303 elements).
6.2.3 Records
===============
Record values are labeled tuples of values. The record value written {
field_1 = v_1; ...; field_n = v_n } associates the value v_i to the record
field field_i, for i = 1 ... n. The current implementation supports records
with up to 2^22 - 1 fields (4194303 fields).
6.2.4 Arrays
==============
Arrays are finite, variable-sized sequences of values of the same type. The
current implementation supports arrays containing to 2^22 - 1 elements (4194303
elements).
6.2.5 Variant values
======================
Variant values are either a constant constructor, or a pair of a non-constant
constructor and a value. The former case is written cconstr; the latter case is
written ncconstr(v), where v is said to be the argument of the non-constant
constructor ncconstr.
The following constants are treated like built-in constant constructors:
-----------------------------
|Constant| Constructor |
-----------------------------
|false |the boolean false |
|true |the boolean true |
|() |the ``unit'' value|
|[] |the empty list |
-----------------------------
The current implementation limits the number of distinct constructors in a
given variant type to at most 249.
6.2.6 Polymorphic variants
============================
Polymorphic variants are an alternate form of variant values, not belonging
explicitly to a predefined variant type, and following specific typing rules.
They can be either constant, written `tag-name, or non-constant, written
`tag-name(v).
6.2.7 Functions
=================
Functional values are mappings from values to values.
6.2.8 Objects
===============
Objects are composed of a hidden internal state which is a record of instance
variables, and a set of methods for accessing and modifying these variables.
The structure of an object is described by the toplevel class that created it.
6.3 Names
*=*=*=*=*=*
Identifiers are used to give names to several classes of language objects and
refer to these objects by name later:
- value names (syntactic class value-name),
- value constructors (constant -- class cconstr-name -- or non-constant --
class ncconstr-name),
- labels (label-name),
- variant tags (tag-name),
- type constructors (typeconstr-name),
- record fields (field-name),
- class names (class-name),
- method names (method-name),
- instance variable names (inst-var-name),
- module names (module-name),
- module type names (modtype-name).
These nine name spaces are distinguished both by the context and by the
capitalization of the identifier: whether the first letter of the identifier is
in lowercase (written lowercase-ident below) or in uppercase (written
capitalized-ident). Underscore is considered a lowercase letter for this
purpose.
Naming objects
--------------
value-name ::= lowercase-ident
| ( operator-name )
operator-name ::= prefix-symbol | infix-symbol | * | = | or | & | :=
cconstr-name ::= capitalized-ident
| false
| true
| [ ]
| ( )
ncconstr-name ::= capitalized-ident
| ::
label-name ::= lowercase-ident
tag-name ::= capitalized-ident
typeconstr-name ::= lowercase-ident
field-name ::= lowercase-ident
module-name ::= capitalized-ident
modtype-name ::= ident
class-name ::= lowercase-ident
inst-var-name ::= lowercase-ident
method-name ::= lowercase-ident
As shown above, prefix and infix symbols as well as some keywords can be
used as value names, provided they are written between parentheses. Keywords
such as '::' and 'false' are also constructor names. The capitalization rules
are summarized in the table below.
----------------------------------------
| Name space |Case of first letter|
----------------------------------------
|Values |lowercase |
|Constructors |uppercase |
|Labels |lowercase |
|Variant tag |uppercase |
|Type constructors|lowercase |
|Record fields |lowercase |
|Classes |lowercase |
|Methods |lowercase |
|Modules |uppercase |
|Module types |any |
----------------------------------------
Referring to named objects
--------------------------
value-path ::= value-name
| module-path . lowercase-ident
cconstr ::= cconstr-name
| module-path . capitalized-ident
ncconstr ::= ncconstr-name
| module-path . capitalized-ident
typeconstr ::= typeconstr-name
| extended-module-path . lowercase-ident
field ::= field-name
| module-path . lowercase-ident
module-path ::= module-name
| module-path . capitalized-ident
extended-module-path ::= module-name
| extended-module-path . capitalized-ident
| extended-module-path ( extended-module-path )
modtype-path ::= modtype-name
| extended-module-path . ident
class-path ::= class-name
| module-path . lowercase-ident
A named object can be referred to either by its name (following the usual
static scoping rules for names) or by an access path prefix . name, where
prefix designates a module and name is the name of an object defined in that
module. The first component of the path, prefix, is either a simple module name
or an access path name_1 . name_2 ..., in case the defining module is itself
nested inside other modules. For referring to type constructors or module
types, the prefix can also contain simple functor applications (as in the
syntactic class extended-module-path above), in case the defining module is the
result of a functor application.
Label names, tag names, method names and instance variable names need not be
qualified: the former three are global labels, while the latter are local to a
class.
6.4 Type expressions
*=*=*=*=*=*=*=*=*=*=*=
typexpr ::= ' ident
| _
| ( typexpr )
| [[?]ident:] typexpr -> typexpr
+
| typexpr { * typexpr }
| typeconstr
| typexpr typeconstr
| ( typexpr { , typexpr } ) typeconstr
| typexpr as ' ident
| [ variant-type ]
| < [..] >
| < method-type { ; method-type } [; ..] >
| # class-path
| typexpr # class-path
| ( typexpr { , typexpr } ) # class-path
| # typeconstr-path [ tag-list ]
| typexpr # typeconstr-path [ tag-list ]
| ( typexpr { , typexpr } ) # typeconstr-path [ tag-list ]
method-type ::= method-name : typexpr
+
tag-list ::= [> {`tag-name} ]
The table below shows the relative precedences and associativity of operators
and non-closed type constructions. The constructions with higher precedences
come first.
--------------------------------------------
| Operator |Associativity|
--------------------------------------------
|Type constructor application|-- |
|* |-- |
|-> |right |
|as |-- |
--------------------------------------------
Type expressions denote types in definitions of data types as well as in type
constraints over patterns and expressions.
Type variables
--------------
The type expression ' ident stands for the type variable named ident. The
type expression _ stands for an anonymous type variable. In data type
definitions, type variables are names for the data type parameters. In type
constraints, they represent unspecified types that can be instantiated by any
type to satisfy the type constraint.
Parenthesized types
-------------------
The type expression ( typexpr ) denotes the same type as typexpr.
Function types
--------------
The type expression typexpr_1 -> typexpr_2 denotes the type of functions
mapping arguments of type typexpr_1 to results of type typexpr_2.
label typexpr_1 -> typexpr_2 denotes the same function type, but the argument
is labeled label.
?label typexpr_1 -> typexpr_2 denotes the type of functions mapping an
optional labeled argument of type typexpr_1 to results of type typexpr_2. That
is, the physical type of the function will be typexpr_1 option -> typexpr_2.
Tuple types
-----------
The type expression typexpr_1 * ... * typexpr_n denotes the type of tuples
whose elements belong to types typexpr_1, ... typexpr_n respectively.
Constructed types
-----------------
Type constructors with no parameter, as in typeconstr, are type expressions.
The type expression typexpr typeconstr, where typeconstr is a type
constructor with one parameter, denotes the application of the unary type
constructor typeconstr to the type typexpr.
The type expression (typexpr_1,...,typexpr_n) typeconstr, where typeconstr is
a type constructor with n parameters, denotes the application of the n-ary type
constructor typeconstr to the types typexpr_1 through typexpr_n.
Recursive types
---------------
The type expression typexpr as ' ident denotes the same type as typexpr, and
also binds the type variable ident to type typexpr both in typexpr and in the
remaining part of the type. If the type variable ident actually occurs in
typexpr, a recursive type is created. Recursive types for which there exists a
recursive path that does not contain an object type constructor are rejected.
Variant types
-------------
variant-type ::= [ tag-spec ] { | tag-spec }
| > [ tag-spec ] { | tag-spec }
+
| < [ | ] tag-spec-full { | tag-spec-full } [ > { `tag-name
} ]
tag-spec ::= `tag-name [ of typexpr ]
tag-spec-full ::= `tag-name [ of typexpr ] { & typexpr }
Variant types describe the values a polymorphic variant may take.
The first case is an exact variant type: all possible tags are known, with
their associated types, and they can all be present. Its structure is fully
known. A special case is the empty type, with no tag, which contains no value.
The second case is an open variant type, describing a polymorphic variant
value: it gives the list of all tags the value could take, with their
associated types. This type is still compatible with a variant type containing
more tags. A special case is the unknown type, which does not define any tag,
and is compatible with any variant type.
The third case is a closed variant type. It gives information about all the
possible tags and their associated types, and which tags are known to
potentially appear in values. The above exact variant type is just an
abbreviation for a closed variant type where all possible tags are also
potentially present.
Full specification of variant tags are only used for non-exact closed types.
They can be understood as a conjunctive type for the argument: it is intended
to have all the types enumerated in the specification.
Such conjunctive constraints may be unsatisfiable. In such a case the
corresponding tag may not be used in a value of this type. This does not mean
that the whole type is not valid: one can still use other available tags.
Object types
------------
An object type < method-type { ; method-type } > is a record of method types.
The type < method-type { ; method-type } ; .. > is the type of an object with
methods and their associated types are described by method-type_1, ...,
method-type_n, and possibly some other methods represented by the ellipsis.
This ellipsis actually is a special kind of type variable (also called row
variable in the literature) that stands for any number of extra method types.
#-types
-------
The type # class-path is a special kind of abbreviation. This abbreviation
unifies with the type of any object belonging to a subclass of class
class-path. It is handled in a special way as it usually hides a type variable
(an ellipsis, representing the methods that may be added in a subclass). In
particular, it vanishes when the ellipsis gets instantiated. Each type
expression # class-path defines a new type variable, so type # class-path -> #
class-path is usually not the same as type # class-path as ' ident -> ' ident.
#-types can also be used to abbreviate variant types. Similarly they express
the presence of a row variable, allowing further refinement of the type.
Precisely, if t has been defined as the type [ `tag_1 a_1 | ... |`tag_n a_n]
then #t is the type [< `tag_1 a_1 | ...|`tag_n a_n], and #t[> `tag_1 ...`tag_k]
is the type [< `tag_1 a_1 | ...|`tag_n a_n > `tag_1 ...`tag_k].
Variant and record types
------------------------
There are no type expressions describing (defined) variant types nor record
types, since those are always named, i.e. defined before use and referred to by
name. Type definitions are described in section 6.8.1.
6.5 Constants
*=*=*=*=*=*=*=*
constant ::= integer-literal
| float-literal
| char-literal
| string-literal
| cconstr
| `tag-name
The syntactic class of constants comprises literals from the four base types
(integers, floating-point numbers, characters, character strings), and constant
constructors from both normal and polymorphic variants.
6.6 Patterns
*=*=*=*=*=*=*=
pattern ::= value-name
| _
| constant
| pattern as value-name
| ( pattern )
| ( pattern : typexpr )
| pattern | pattern
| ncconstr pattern
| `tag-name pattern
| #typeconstr-name
| pattern { , pattern }
| { field = pattern { ; field = pattern } }
| [ pattern { ; pattern } ]
| pattern :: pattern
The table below shows the relative precedences and associativity of operators
and non-closed pattern constructions. The constructions with higher precedences
come first.
---------------------------------------
| Operator |Associativity|
---------------------------------------
|Constructor application|-- |
|:: |right |
|, |-- |
|| |left |
|as |-- |
---------------------------------------
Patterns are templates that allow selecting data structures of a given shape,
and binding identifiers to components of the data structure. This selection
operation is called pattern matching; its outcome is either ``this value does
not match this pattern'', or ``this value matches this pattern, resulting in
the following bindings of names to values''.
Variable patterns
-----------------
A pattern that consists in a value name matches any value, binding the name
to the value. The pattern _ also matches any value, but does not bind any name.
Patterns are linear: a variable cannot appear several times in a given
pattern. In particular, there is no way to test for equality between two parts
of a data structure using only a pattern (but when guards can be used for this
purpose).
Constant patterns
-----------------
A pattern consisting in a constant matches the values that are equal to this
constant.
Alias patterns
--------------
The pattern pattern_1 as value-name matches the same values as pattern_1. If
the matching against pattern_1 is successful, the name name is bound to the
matched value, in addition to the bindings performed by the matching against
pattern_1.
Parenthesized patterns
----------------------
The pattern ( pattern_1 ) matches the same values as pattern_1. A type
constraint can appear in a parenthesized pattern, as in ( pattern_1 : typexpr
). This constraint forces the type of pattern_1 to be compatible with type.
``Or'' patterns
---------------
The pattern pattern_1 | pattern_2 represents the logical ``or'' of the two
patterns pattern_1 and pattern_2. A value matches pattern_1 | pattern_2 either
if it matches pattern_1 or if it matches pattern_2. The two sub-patterns
pattern_1 and pattern_2 must bind exactly the same identifiers to values having
the same types. The bindings performed by matching against an ``or'' pattern
are either those performed by the matching against pattern_1, if it succeeds,
or those performed by the matching against pattern_2, if it succeeds. If both
matchings succeed, it is undefined which set of bindings is selected.
Variant patterns
----------------
The pattern ncconstr pattern_1 matches all variants whose constructor is
equal to ncconstr, and whose argument matches pattern_1.
The pattern pattern_1 :: pattern_2 matches non-empty lists whose heads match
pattern_1, and whose tails match pattern_2. This pattern behaves like ( :: ) (
pattern_1 , pattern_2 ).
The pattern [ pattern_1 ; ... ; pattern_n ] matches lists of length n whose
elements match pattern_1 ...pattern_n, respectively. This pattern behaves like
pattern_1 :: ... :: pattern_n :: [].
Polymorphic variant patterns
----------------------------
The pattern `tag-name pattern_1 matches all polymorphic variants whose tag is
equal to tag-name, and whose argument matches pattern_1.
Variant abbreviation patterns
-----------------------------
If the type [('a,'b,...)] typeconstr = [`tag_1 t_1 | ... | `tag_n t_n] is
defined, then the pattern #typeconstr is a shorthand for the or-pattern
(`tag_1(_ : t_1) | ... | `tag_n(_ : t_n)). It matches all values of type
#typeconstr.
Tuple patterns
--------------
The pattern pattern_1 , ... , pattern_n matches n-tuples whose components
match the patterns pattern_1 through pattern_n. That is, the pattern matches
the tuple values (v_1, ..., v_n) such that pattern_i matches v_i for i = 1,...
, n.
Record patterns
---------------
The pattern { field_1 = pattern_1 ; ... ; field_n = pattern_n } matches
records that define at least the fields field_1 through field_n, and such that
the value associated to field_i match the pattern pattern_i, for i = 1,... , n.
The record value can define more fields than field_1 ...field_n; the values
associated to these extra fields are not taken into account for matching.
6.7 Expressions
*=*=*=*=*=*=*=*=*
expr ::= value-path
| constant
| ( expr )
| begin expr end
| ( expr : typexpr )
| expr , expr { , expr }
| ncconstr expr
| `tag-name expr
| expr :: expr
| [ expr { ; expr } ]
| [| expr { ; expr } |]
| { field = expr { ; field = expr } }
+
| expr { argument }
| prefix-symbol expr
| expr infix-op expr
| expr . field
| expr . field <- expr
| expr .( expr )
| expr .( expr ) <- expr
| expr .[ expr ]
| expr .[ expr ] <- expr
| if expr then expr [ else expr ]
| while expr do expr done
| for ident = expr ( to | downto ) expr do expr done
| expr ; expr
| match expr with pattern-matching
| function pattern-matching
| fun multiple-matching
| try expr with pattern-matching
| let [rec] let-binding { and let-binding } in expr
| new class-path
| expr # method-name
| ( expr :> typexpr )
| ( expr : typexpr :> typexpr )
| {< inst-var-name = expr { ; inst-var-name = expr } >}
argument ::= expr
| ~ label-name
| ~ label-name : expr
| ? label-name
| ? label-name : expr
pattern-matching ::= [ | ] pattern [when expr] -> expr { | pattern [when
expr] -> expr }
+
multiple-matching ::= { parameter } [when expr] -> expr
let-binding ::= pattern [: typexpr] = expr
+
| value-name { parameter } [: typexpr] = expr
parameter ::= pattern
| ~ label-name
| ~ ( label-name [: typexpr] )
| ~ label-name : pattern
| ? label-name
| ? ( label-name [: typexpr] [= expr] )
| ? label-name : pattern
| ? label-name : ( pattern [: typexpr] [= expr] )
infix-op ::= infix-symbol
| * | = | or | &
The table below shows the relative precedences and associativity of operators
and non-closed constructions. The constructions with higher precedence come
first. For infix and prefix symbols, we write ``*...'' to mean ``any symbol
starting with *''.
---------------------------------------------------------------------
| Construction or operator |Associativity|
---------------------------------------------------------------------
|prefix-symbol |-- |
|. .( .[ |-- |
|function application |left |
|constructor application |-- |
|- -. (prefix) |-- |
|**... |right |
|*... /... %... mod |left |
|+... -... |left |
|:: |right |
|@...^... |right |
|comparisons (= == < etc.), all other infix symbols|left |
|not |-- |
|& && |left |
|or || |left |
|, |-- |
|<- := |right |
|if |-- |
|; |right |
|let match fun function try |-- |
---------------------------------------------------------------------
6.7.1 Basic expressions
=========================
Constants
---------
Expressions consisting in a constant evaluate to this constant.
Value paths
-----------
Expressions consisting in an access path evaluate to the value bound to this
path in the current evaluation environment. The path can be either a value name
or an access path to a value component of a module.
Parenthesized expressions
-------------------------
The expressions ( expr ) and begin expr end have the same value as expr. Both
constructs are semantically equivalent, but it is good style to use begin ...
end inside control structures:
<<
if ... then begin ... ; ... end else begin ... ; ... end
>>
and ( ... ) for the other grouping situations.
Parenthesized expressions can contain a type constraint, as in ( expr : type
). This constraint forces the type of expr to be compatible with type.
Parenthesized expressions can also contain coercions ( expr [: type] :> type)
(see subsection 6.7.5 below).
Function application
--------------------
Function application is denoted by juxtaposition of (possibly labeled)
expressions. The expression expr argument_1 ... argument_n evaluates the
expression expr and those appearing in argument_1 to argument_n. The expression
expr must evaluate to a functional value f, which is then applied to the values
of argument_1, ..., argument_n.
If a parameter is specified as optional (label prefixed by ?) in expr's type,
the corresponding argument will be automatically wrapped with the constructor
Some, except if the argument itself is also prefixed by ?, in which case it is
passed as is.
The order in which the expressions expr, argument_1, ..., argument_n are
evaluated is not specified.
The way in which arguments and parameters are matched depends on the
compilation mode. In the default, or classic mode, non optional arguments need
not be explicitly labeled. They will match the parameters in the order of
definition. In case arguments are labeled, the label is checked against the
parameter at compile time. Optional arguments must be labeled. They will be
reordered according to their labels, but a group of contiguous optional
parameters in expr's type must be matched by a group of contiguous labeled
arguments. If there is one or more non-labeled arguments after the optional
ones, optional parameters with no matching argument will be defaulted, that is
the value None will be passed for them. Otherwise they will be kept, and the
result of the function will still be a function of the missing optional
parameters.
In the strict, or commuting label mode, parameters and arguments are matched
according to their labels. The order is irrelevent, except if several arguments
have the same label, or no label. The criterion for defaulting missing optional
arguments is whether a non-labeled parameter following them in f was matched by
an argument or not. If some parameters were not matched in the process, the
result will be a new function from these parameters to the body of f.
Function definition
-------------------
Two syntactic forms are provided to define functions. The first form is
introduced by the keyword function:
function pattern -> expr
1 1
| ...
| pattern -> expr
n n
This expression evaluates to a functional value with one argument. When this
function is applied to a value v, this value is matched against each pattern
pattern_1 to pattern_n. If one of these matchings succeeds, that is, if the
value v matches the pattern pattern_i for some i, then the expression expr_i
associated to the selected pattern is evaluated, and its value becomes the
value of the function application. The evaluation of expr_i takes place in an
environment enriched by the bindings performed during the matching.
If several patterns match the argument v, the one that occurs first in the
function definition is selected. If none of the patterns matches the argument,
the exception Match_failure is raised.
The other form of function definition is introduced by the keyword fun:
fun parameter_1 ... parameter_n -> expr
This expression is equivalent to:
fun parameter_1 -> ... fun parameter_n -> expr
Functions of the form fun optlabel ( pattern = expr_0 ) -> expr are
equivalent to
fun optlabel x -> let pattern = match x with Some x -> x | None -> expr
in expr
0
where x is a fresh variable. When expr_0 will be evaluated is left
unspecified.
After these two transformations, expressions are of the form
fun [label_1] pattern_1 -> ... fun [label_n] pattern_n -> expr
If we ignore labels, which will only be meaningful at function application,
this is equivalent to
function pattern_1 -> ... function pattern_n -> expr
That is, the fun expression above evaluates to a curried function with n
arguments: after applying this function n times to the values v_1 ... v_m, the
values will be matched in parallel against the patterns pattern_1 ...
pattern_n. If the matching succeeds, the function returns the value of expr in
an environment enriched by the bindings performed during the matchings. If the
matching fails, the exception Match_failure is raised.
Guards in pattern-matchings
---------------------------
Cases of a pattern matching (in the function, fun, match and try constructs)
can include guard expressions, which are arbitrary boolean expressions that
must evaluate to true for the match case to be selected. Guards occur just
before the -> token and are introduced by the when keyword:
function pattern [when cond ] -> expr
1 1 1
| ...
| pattern [when cond ] -> expr
n n n
Matching proceeds as described before, except that if the value matches some
pattern pattern_i which has a guard cond_i, then the expression cond_i is
evaluated (in an environment enriched by the bindings performed during
matching). If cond_i evaluates to true, then expr_i is evaluated and its value
returned as the result of the matching, as usual. But if cond_i evaluates to
false, the matching is resumed against the patterns following pattern_i.
Local definitions
-----------------
The let and let rec constructs bind value names locally. The construct
let pattern_1 = expr_1 and ... and pattern_n = expr_n in expr
evaluates expr_1 ... expr_n in some unspecified order, then matches their
values against the patterns pattern_1 ... pattern_n. If the matchings succeed,
expr is evaluated in the environment enriched by the bindings performed during
matching, and the value of expr is returned as the value of the whole let
expression. If one of the matchings fails, the exception Match_failure is
raised.
An alternate syntax is provided to bind variables to functional values:
instead of writing
let ident = fun parameter_1 ... parameter_m -> expr
in a let expression, one may instead write
let ident parameter_1 ... parameter_m = expr
Recursive definitions of names are introduced by let rec:
let rec pattern_1 = expr_1 and ... and pattern_n = expr_n in expr
The only difference with the let construct described above is that the
bindings of names to values performed by the pattern-matching are considered
already performed when the expressions expr_1 to expr_n are evaluated. That is,
the expressions expr_1 to expr_n can reference identifiers that are bound by
one of the patterns pattern_1, ..., pattern_n, and expect them to have the same
value as in expr, the body of the let rec construct.
The recursive definition is guaranteed to behave as described above if the
expressions expr_1 to expr_n are function definitions (fun ... or function
...), and the patterns pattern_1 ... pattern_n are just value names, as in:
let rec name_1 = fun ... and ... and name_n = fun ... in expr
This defines name_1 ... name_n as mutually recursive functions local to
expr.
The behavior of other forms of let rec definitions is
implementation-dependent. The current implementation also supports a certain
class of recursive definitions of non-functional values, such as
let rec name_1 = 1 :: name_2 and name_2 = 2 :: name_1 in expr
which binds name_1 to the cyclic list 1::2::1::2::..., and name_2 to the
cyclic list 2::1::2::1::...Informally, the class of accepted definitions
consists of those definitions where the defined names occur only inside
function bodies or as argument to a data constructor.
6.7.2 Control structures
==========================
Sequence
--------
The expression expr_1 ; expr_2 evaluates expr_1 first, then expr_2, and
returns the value of expr_2.
Conditional
-----------
The expression if expr_1 then expr_2 else expr_3 evaluates to the value of
expr_2 if expr_1 evaluates to the boolean true, and to the value of expr_3 if
expr_1 evaluates to the boolean false.
The else expr_3 part can be omitted, in which case it defaults to else ().
Case expression
---------------
The expression
match expr
with pattern -> expr
1 1
| ...
| pattern -> expr
n n
matches the value of expr against the patterns pattern_1 to pattern_n. If
the matching against pattern_i succeeds, the associated expression expr_i is
evaluated, and its value becomes the value of the whole match expression. The
evaluation of expr_i takes place in an environment enriched by the bindings
performed during matching. If several patterns match the value of expr, the one
that occurs first in the match expression is selected. If none of the patterns
match the value of expr, the exception Match_failure is raised.
Boolean operators
-----------------
The expression expr_1 && expr_2 evaluates to true if both expr_1 and expr_2
evaluate to true; otherwise, it evaluates to false. The first component,
expr_1, is evaluated first. The second component, expr_2, is not evaluated if
the first component evaluates to false. Hence, the expression expr_1 && expr_2
behaves exactly as
if expr_1 then expr_2 else false.
The expression expr_1 || expr_2 evaluates to true if one of expr_1 and expr_2
evaluates to true; otherwise, it evaluates to false. The first component,
expr_1, is evaluated first. The second component, expr_2, is not evaluated if
the first component evaluates to true. Hence, the expression expr_1 || expr_2
behaves exactly as
if expr_1 then true else expr_2.
The boolean operator & is synonymous for &&. The boolean operator or is
synonymous for ||.
Loops
-----
The expression while expr_1 do expr_2 done repeatedly evaluates expr_2 while
expr_1 evaluates to true. The loop condition expr_1 is evaluated and tested at
the beginning of each iteration. The whole while ... done expression evaluates
to the unit value ().
The expression for name = expr_1 to expr_2 do expr_3 done first evaluates
the expressions expr_1 and expr_2 (the boundaries) into integer values n and p.
Then, the loop body expr_3 is repeatedly evaluated in an environment where name
is successively bound to the values n, n+1, ..., p-1, p. The loop body is
never evaluated if n > p.
The expression for name = expr_1 downto expr_2 do expr_3 done evaluates
similarly, except that name is successively bound to the values n, n-1, ...,
p+1, p. The loop body is never evaluated if n < p.
In both cases, the whole for expression evaluates to the unit value ().
Exception handling
------------------
The expression
try expr
with pattern -> expr
1 1
| ...
| pattern -> expr
n n
evaluates the expression expr and returns its value if the evaluation of
expr does not raise any exception. If the evaluation of expr raises an
exception, the exception value is matched against the patterns pattern_1 to
pattern_n. If the matching against pattern_i succeeds, the associated
expression expr_i is evaluated, and its value becomes the value of the whole
try expression. The evaluation of expr_i takes place in an environment enriched
by the bindings performed during matching. If several patterns match the value
of expr, the one that occurs first in the try expression is selected. If none
of the patterns matches the value of expr, the exception value is raised again,
thereby transparently ``passing through'' the try construct.
6.7.3 Operations on data structures
=====================================
Products
--------
The expression expr_1 , ... , expr_n evaluates to the n-tuple of the values
of expressions expr_1 to expr_n. The evaluation order for the subexpressions is
not specified.
Variants
--------
The expression ncconstr expr evaluates to the variant value whose constructor
is ncconstr, and whose argument is the value of expr.
For lists, some syntactic sugar is provided. The expression expr_1 :: expr_2
stands for the constructor ( :: ) applied to the argument ( expr_1 , expr_2 ),
and therefore evaluates to the list whose head is the value of expr_1 and whose
tail is the value of expr_2. The expression [ expr_1 ; ... ; expr_n ] is
equivalent to expr_1 :: ... :: expr_n :: [], and therefore evaluates to the
list whose elements are the values of expr_1 to expr_n.
Polymorphic variants
--------------------
The expression `tag-name expr evaluates to the variant value whose tag is
tag-name, and whose argument is the value of expr.
Records
-------
The expression { field_1 = expr_1 ; ... ; field_n = expr_n } evaluates to the
record value { field_1 = v_1 ; ... ; field_n = v_n }, where v_i is the value of
expr_i for i = 1,... , n. The fields field_1 to field_n must all belong to the
same record types; all fields belonging to this record type must appear exactly
once in the record expression, though they can appear in any order. The order
in which expr_1 to expr_n are evaluated is not specified.
The expression expr_1 . field evaluates expr_1 to a record value, and returns
the value associated to field in this record value.
The expression expr_1 . field <- expr_2 evaluates expr_1 to a record value,
which is then modified in-place by replacing the value associated to field in
this record by the value of expr_2. This operation is permitted only if field
has been declared mutable in the definition of the record type. The whole
expression expr_1 . field <- expr_2 evaluates to the unit value ().
Arrays
------
The expression [| expr_1 ; ... ; expr_n |] evaluates to a n-element array,
whose elements are initialized with the values of expr_1 to expr_n
respectively. The order in which these expressions are evaluated is
unspecified.
The expression expr_1 .( expr_2 ) returns the value of element number expr_2
in the array denoted by expr_1. The first element has number 0; the last
element has number n-1, where n is the size of the array. The exception
Invalid_argument is raised if the access is out of bounds.
The expression expr_1 .( expr_2 ) <- expr_3 modifies in-place the array
denoted by expr_1, replacing element number expr_2 by the value of expr_3. The
exception Invalid_argument is raised if the access is out of bounds. The value
of the whole expression is ().
Strings
-------
The expression expr_1 .[ expr_2 ] returns the value of character number
expr_2 in the string denoted by expr_1. The first character has number 0; the
last character has number n-1, where n is the length of the string. The
exception Invalid_argument is raised if the access is out of bounds.
The expression expr_1 .[ expr_2 ] <- expr_3 modifies in-place the string
denoted by expr_1, replacing character number expr_2 by the value of expr_3.
The exception Invalid_argument is raised if the access is out of bounds. The
value of the whole expression is ().
6.7.4 Operators
=================
Symbols from the class infix-symbols, as well as the keywords *, =, or and &,
can appear in infix position (between two expressions). Symbols from the class
prefix-symbols can appear in prefix position (in front of an expression).
Infix and prefix symbols do not have a fixed meaning: they are simply
interpreted as applications of functions bound to the names corresponding to
the symbols. The expression prefix-symbol expr is interpreted as the
application ( prefix-symbol ) expr. Similarly, the expression expr_1
infix-symbol expr_2 is interpreted as the application ( infix-symbol ) expr_1
expr_2.
The table below lists the symbols defined in the initial environment and
their initial meaning. (See the description of the standard library module
Pervasive in chapter 18 for more details). Their meaning may be changed at any
time using let ( infix-op ) name_1 name_2 = ...
------------------------------------------------
| Operator | Initial meaning |
------------------------------------------------
|+ |Integer addition. |
|- (infix) |Integer subtraction. |
|- (prefix) |Integer negation. |
|* |Integer multiplication. |
|/ |Integer division. Raise |
| |Division_by_zero if second |
| |argument is zero. The result is |
| |unspecified if either argument is |
| |negative. |
|mod |Integer modulus. Raise |
| |Division_by_zero if second |
| |argument is zero. The result is |
| |unspecified if either argument is |
| |negative. |
|land |Bitwise logical ``and'' on |
| |integers. |
|lor |Bitwise logical ``or'' on |
| |integers. |
|lxor |Bitwise logical ``exclusive or'' |
| |on integers. |
|lsl |Bitwise logical shift left on |
| |integers. |
|lsr |Bitwise logical shift right on |
| |integers. |
|asr |Bitwise arithmetic shift right on |
| |integers. |
|+. |Floating-point addition. |
|-. (infix) |Floating-point subtraction. |
|-. (prefix)|Floating-point negation. |
|*. |Floating-point multiplication. |
|/. |Floating-point division. |
|** |Floating-point exponentiation. |
|@ |List concatenation. |
|^ |String concatenation. |
|! |Dereferencing (return the current |
| |contents of a reference). |
|:= |Reference assignment (update the |
| |reference given as first argument |
| |with the value of the second |
| |argument). |
|= |Structural equality test. |
|<> |Structural inequality test. |
|== |Physical equality test. |
|!= |Physical inequality test. |
|< |Test ``less than''. |
|<= |Test ``less than or equal''. |
|> |Test ``greater than''. |
|>= |Test ``greater than or equal''. |
------------------------------------------------
6.7.5 Objects
===============
Object creation
---------------
When class-path evaluates to a class body, new class-path evaluates to an
object containing the instance variables and methods of this class.
When class-path evaluates to a class function, new class-path evaluates to a
function expecting the same number of arguments and returning a new object of
this class.
Message sending
---------------
The expression expr # method-name invokes the method method-name of the
object denoted by expr.
Coercion
--------
The type of an object can be coerced (weakened) to a supertype. The
expression ( expr :> typexpr ) coerces the expression expr to type typexpr. The
expression ( expr : typexpr_1 :> typexpr_2 ) coerces the expression expr from
type typexpr_1 to type typexpr_2. The former operator will sometimes fail to
coerce an expression expr from a type t_1 to a type t_2 even if type t_1 is a
subtype of type t_2. In this case, the latter operator should be used.
In a class definition, coercion to the type this class defines is the
identity, as this type abbreviation is not yet completely defined.
Object duplication
------------------
An object can be duplicated using the library function Oo.copy (see section
19.20). Inside a method, the expression {< inst-var-name = expr { ;
inst-var-name = expr } >} returns a copy of self with the given instance
variables replaced by the values of the associated expressions; other instance
variables have the same value in the returned object as in self.
6.8 Type and exception definitions
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
6.8.1 Type definitions
========================
Type definitions bind type constructors to data types: either variant types,
record types, type abbreviations, or abstract data types. They also bind the
value constructors and record fields associated with the definition.
type-definition ::= type typedef { and typedef }
typedef ::= [type-params] typeconstr-name [type-information]
type-information ::= [type-equation] [type-representation] {
type-constraint }
type-equation ::= = typexpr
type-representation ::= = constr-decl { | constr-decl }
| = { field-decl { ; field-decl } }
type-params ::= type-param
| ( type-param { , type-param } )
type-param ::= ' ident
| + ' ident
| - ' ident
constr-decl ::= cconstr-name
| ncconstr-name of typexpr
field-decl ::= field-name : typexpr
| mutable field-name : typexpr
type-constraint ::= constraint ' ident = typexpr
Type definitions are introduced by the type keyword, and consist in one or
several simple definitions, possibly mutually recursive, separated by the and
keyword. Each simple definition defines one type constructor.
A simple definition consists in a lowercase identifier, possibly preceded by
one or several type parameters, and followed by an optional type equation, then
an optional type representation, and then a constraint clause. The identifier
is the name of the type constructor being defined.
The optional type parameters are either one type variable ' ident, for type
constructors with one parameter, or a list of type variables
('ident_1,...,'ident_n), for type constructors with several parameters. Each
type parameter may be prefixed by a variance constraint + (resp. -) indicating
that the parameter is covariant (resp. contravariant). These type parameters
can appear in the type expressions of the right-hand side of the definition,
restricted eventually by a variance constraint ; i.e. a covariant parameter may
only appear on the right side of a functional arrow (more precisely, follow the
left branch of an even number of arrows), and a convariant parameter only the
left side (left branch of an odd number of arrows).
The optional type equation = typexpr makes the defined type equivalent to the
type expression typexpr on the right of the = sign: one can be substituted for
the other during typing. If no type equation is given, a new type is generated:
the defined type is incompatible with any other type.
The optional type representation describes the data structure representing
the defined type, by giving the list of associated constructors (if it is a
variant type) or associated fields (if it is a record type). If no type
representation is given, nothing is assumed on the structure of the type
besides what is stated in the optional type equation.
The type representation = constr-decl { | constr-decl } describes a variant
type. The constructor declarations constr-decl_1, ..., constr-decl_n describe
the constructors associated to this variant type. The constructor declaration
ncconstr-name of typexpr declares the name ncconstr-name as a non-constant
constructor, whose argument has type typexpr. The constructor declaration
cconstr-name declares the name cconstr-name as a constant constructor.
Constructor names must be capitalized.
The type representation = { field-decl { ; field-decl } } describes a record
type. The field declarations field-decl_1, ..., field-decl_n describe the
fields associated to this record type. The field declaration field-name :
typexpr declares field-name as a field whose argument has type typexpr. The
field declaration mutable field-name : typexpr behaves similarly; in addition,
it allows physical modification over the argument to this field. Immutable
fields are covariant, but mutable fields are neither covariant nor
contravariant.
The two components of a type definition, the optional equation and the
optional representation, can be combined independently, giving rise to four
typical situations:
Abstract type: no equation, no representation.
When appearing in a module signature, this definition specifies nothing on the
type constructor, besides its number of parameters: its representation is
hidden and it is assumed incompatible with any other type.
Type abbreviation: an equation, no representation.
This defines the type constructor as an abbreviation for the type expression
on the right of the = sign.
New variant type or record type: no equation, a representation.
This generates a new type constructor and defines associated constructors or
fields, through which values of that type can be directly built or
inspected.
Re-exported variant type or record type: an equation, a representation.
In this case, the type constructor is defined as an abbreviation for the type
expression given in the equation, but in addition the constructors or fields
given in the representation remain attached to the defined type constructor.
The type expression in the equation part must agree with the representation:
it must be of the same kind (record or variant) and have exactly the same
constructors or fields, in the same order, with the same arguments.
The type variables appearing as type parameters can optionally be prefixed by
+ or - to indicate that the type constructor is covariant or contravariant with
respect to this parameter. This variance information is used to decide
subtyping relations when checking the validity of >: coercions (see section
6.7.5).
For instance, type +'a t declares t as an abstract type that is covariant in
its parameter; this means that if the type tau is a subtype of the type sigma,
then tau t is a subtype of sigma t. Similarly, type -'a t declares that the
abstract type t is contravariant in its parameter: if tau is subtype of sigma,
then sigma t is subtype of tau t. If no + or - variance annotation is
given, the type constructor is assumed invariant in the corresponding
parameter. For instance, the abstract type declaration type 'a t means that tau
t is neither a subtype nor a supertype of sigma t if tau is subtype of
sigma.
The variance indicated by the + and - annotations on parameters are required
only for abstract types. For abbreviations, variant types or record types, the
variance properties of the type constructor are inferred from its definition,
and the variance annotations are only checked for conformance with the
definition.
The construct constraint ' ident = typexpr allows to specify type
parameters. Any actual type argument corresponding to the type parameter ident
has to be an instance of typexpr (more precisely, ident and typexpr are
unified). Type variables of typexpr can appear in the type equation and the
type declaration.
6.8.2 Exception definitions
=============================
exception-definition ::= exception constr-decl
| exception cconstr-name = cconstr
| exception ncconstr-name = ncconstr
Exception definitions add new constructors to the built-in variant type `exn'
of exception values. The constructors are declared as for a definition of a
variant type.
The form exception constr-decl generates a new exception, distinct from all
other exceptions in the system. The form exception name = constr gives an
alternate name to an existing exception.
6.9 Classes
*=*=*=*=*=*=*
Classes are defined using a small language, similar to the module language.
6.9.1 Class types
===================
Class types are the class-level equivalent of type expressions: they specify
the general shape and type properties of classes.
class-type ::=
| class-body-type
| [[?]label]typexpr -> class-type
class-body-type ::= object [( typexpr )] {class-field-spec} end
| class-path
| [ typexpr {, typexpr} ] class-path
class-field-spec ::= inherit class-type
| val [mutable] inst-var-name : typexpr
| method [private] method-name : typexpr
| method [private] virtual method-name : typexpr
| constraint typexpr = typexpr
Simple class expressions
------------------------
The expression class-path is equivalent to the class type bound to the name
class-path. Similarly, the expression [ typexpr_1 , ... typexpr_n ] class-path
is equivalent to the parametric class type bound to the name class-path, in
which type parameters have been instanciated to respectively typexpr_1,
...typexpr_n.
Class function type
-------------------
The class type expression typexpr -> class-type is the type of class
functions (functions from values to classes) that take as argument a value of
type typexpr and return as result a class of type class-type.
Class body type
---------------
The class type expression object [( typexpr )] {class-field-spec} end is the
type of a class body. It specifies its instance variables and methods. In this
type, typexpr is match agains self type, therefore provinding a binding for
self type.
A class body will match a class body type if it provides definitions for all
the components specified in the class type, and these definitions meet the type
requirements given in the class type. Furthermore, all methods either virtual
or public present in the class body must also be present in the class type (on
the other hand, some instance variables and concrete private methods may be
omitted). A virtual method will match a concrete method, thus allowing to
forget its implementation. An immutable instance variable will match a mutable
instance variable.
Inheritance
-----------
The inheritance construct inherit class-type allows to include methods and
instance variables from other classes types. The instance variable and method
types from this class type are added into the current class type.
Instance variable specification
-------------------------------
A specification of an instance variable is written val [mutable]
inst-var-name : typexpr, where inst-var-name is the name of the instance
variable and typexpr its expected type. The flag mutable indicates whether this
instance variable can be physically modified.
An instance variable specification will hide any previous specification of an
instance variable of the same name.
Method specification
--------------------
A specification of an method is written method [private] method-name :
typexpr, where method-name is the name of the method and typexpr its expected
type. The flag private indicates whether the method can be accessed from
outside the class.
Several specification for the same method must have compatible types.
Virtual method specification
----------------------------
Virtual method specification is written method [private] virtual method-name
: typexpr, where method-name is the name of the method and typexpr its expected
type.
Constraints on type parameters
------------------------------
The construct constraint typexpr_1 = typexpr_2 forces the two type
expressions to be equals. This is typically used to specify type parameters:
they can be that way be bound to a specified type expression.
6.9.2 Class expressions
=========================
Class expressions are the class-level equivalent of value expressions: they
evaluate to classes, thus providing implementations for the specifications
expressed in class types.
class-expr ::= class-path
| [ typexpr {, typexpr} ] class-path
| ( class-expr )
| ( class-expr : class-type )
+
| class-expr {argument}
+
| fun {parameter} -> class-expr
| let [rec] let-binding {and let-binding} in class-expr
| object [( pattern [: typexpr] )] { class-field } end
class-field ::= inherit class-expr [as value-name]
| val [mutable] inst-var-name = expr
| method [private] method-name {pattern} = expr
| method [private] virtual method-name : typexpr
| constraint typexpr = typexpr
| initializer expr
Simple class expressions
------------------------
The expression class-path evaluates to the class bound to the name
class-path. Similarly, the expression [ typexpr_1 , ... typexpr_n ] class-path
evaluates to the parametric class bound to the name class-path, in which type
parameters have been instanciated to respectively typexpr_1, ...typexpr_n.
The expression ( class-expr ) evaluates to the same module as class-expr.
The expression ( class-expr : class-type ) checks that class-type match the
type of class-expr (that is, that the implementation class-expr meets the type
specification class-type). The whole expression evaluates to the same class as
class-expr, except that all components not specified in class-type are hidden
and can no longer be accessed.
Class application
-----------------
Class application is denoted by juxtaposition of (possibly labeled)
expressions. Evaluation works as for expression application.
Class function
--------------
The expression fun [[?]label]pattern -> class-expr evaluates to a function
from values to classes. When this function is applied to a value v, this value
is matched against the pattern pattern and the result is the result of the
evaluation of class-expr in the extended environment.
Conversion from functions with default values to functions with patterns only
works identically for class functions as for normal functions.
The expression
fun parameter_1 ... parameter_n -> class-expr
is a short form for
fun parameter_1 -> ... fun parameter_n -> expr
Local definitions
-----------------
The let and let rec constructs bind value names locally, as for the core
language expressions.
Class body
----------
The expression object ( pattern [: typexpr] ) { class-field } end denotes a
class body. This is the prototype for an object : it lists the instance
variables and methods of an objet of this class.
A class body is a class value: it is not evaluated at once. Rather, its
components are evaluated each time an object is created.
In a class body, the pattern ( pattern [: typexpr] ) is matched against self,
therefore provinding a binding for self and self type. Self can only be used in
method and initializers.
Self type cannot be a closed object type, so that the class remains
extensible.
Inheritance
-----------
The inheritance construct inherit class-expr allows to reuse methods and
instance variables from other classes. The class expression class-expr must
evaluate to a class body. The instance variables, methods and initializers from
this class body are added into the current class. The addition of a method will
override any previously defined methods of the same name.
An ancestor can be bound by prepending the construct as value-name to the
inheritance construct above. value-name is not a true variable and can only be
used to select a method, i.e. in an expression value-name # method-name. This
gives access to the method method-name as it was defined in the parent class
even if it is redefined in the current class. The scope of an ancestor binding
is limited to the current class. The ancestor method may be called from a
subclass but only indirectly.
Instance variable definition
----------------------------
The definition val [mutable] inst-var-name = expr adds an instance variable
inst-var-name whose initial value is the value of expression expr. Several
variables of the same name can be defined in the same class. The flag mutable
allows physical modification of this variable by methods.
An instance variables can only be used in the following methods and
initializers of the class.
Method definition
-----------------
Method definition is written method method-name = expr. The definition of a
method overrides any previous definition of this method. The method will be
public (that is, not private) if any of the definition states so.
A private method, method private method-name = expr, is a method that can
only be invoked on self (from other methods of the current class as well as of
subclasses of the current class). This invocation is performed using the
expression value-name # method-name, where value-name is directly bound to self
at the beginning of the class definition. Private methods do not appear in
object types.
Some special expressions are available in method bodies for manipulating
instance variables and duplicating self:
expr ::= ...
| inst-var-name <- expr
| {< [ inst-var-name = expr { ; inst-var-name = expr } ] >}
The expression inst-var-name <- expr modifies in-place the current object by
replacing the value associated to inst-var-name by the value of expr. Of
course, this instance variable must have been declared mutable.
The expression {< [ inst-var-name = expr { ; inst-var-name = expr } ] >}
evaluates to a copy of the current object in which the values of instance
variables inst-var-name_1, ..., inst-var-name_n have been replaced by the
values of the corresponding expressions expr_1, ..., expr_n.
Virtual method definition
-------------------------
Method specification is written method [private] virtual method-name :
typexpr. It specifies whether the method is public or private, and gives its
type.
Constraints on type parameters
------------------------------
The construct constraint typexpr_1 = typexpr_2 forces the two type
expressions to be equals. This is typically used to specify type parameters:
they can be that way be bound to a specified type expression.
Initializers
------------
A class initializer initializer expr specifies an expression that will be
evaluated when an object will be created from the class, once all the instance
variables have been initialized.
6.9.3 Class definitions
=========================
class-definition ::= class class-binding { and class-binding }
class-binding ::= [virtual] [[ type-parameters ]] class-name { pattern
} [: class-type] = class-expr
type-parameters ::= ' ident { , ' ident }
A class definition class class-binding { and class-binding } is recursive.
Each class-binding defines a class-name that can be used in the whole
expression except for inheritance. It can also be used for inheritance, but
only in the definitions that follow its own.
A class binding binds the class name class-name to the value of expression
class-expr. It also binds the class type class-name to the type of the class,
and defines two type abbreviations : class-name and # class-name. The first one
is the type of objects of this class, while the second is more general as it
unifies with the type of any object belonging to a subclass (see section 6.4).
Virtual class
-------------
A class must be flagged virtual if one of its methods is virtual (that is,
appears in the class type, but is not actually defined). Objects cannot be
created from a virtual class.
Type parameters
---------------
The class type parameters correspond to the ones of the class type and of the
two type abbreviations defined by the class binding. They must be bound to
actual types in the class definition using type constraints. So that the
abbreviations are well-formed, type variables of the inferred type of the class
must either be type parameters or be bound in the constraint clause.
6.9.4 Class specification
===========================
class-specification ::= class class-spec { and class-spec }
class-spec ::= [virtual] [[ type-parameters ]] class-name :
class-type
This is the counterpart in signatures of class definitions. A class
specification matches a class definition if they have the same type parameters
and their types match.
6.9.5 Class type definitions
==============================
classtype-definition ::= class type classtype-def { and classtype-def }
classtype-def ::= [virtual] [[ type-parameters ]] class-name =
class-body-type
A class type definition class class-name = class-body-type defines an
abbreviation class-name for the class body type class-body-type. As for class
definitions, two type abbreviations class-name and # class-name are also
defined. The definition can be parameterized by some type parameters. If any
method in the class type body is virtual, the definition must be flagged
virtual.
Two class type definitions match if they have the same type parameters and
the types they expand to match.
6.10 Module types (module specifications)
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
Module types are the module-level equivalent of type expressions: they
specify the general shape and type properties of modules.
module-type ::= modtype-path
| sig { specification [;;] } end
| functor ( module-name : module-type ) -> module-type
| module-type with mod-constraint { and mod-constraint }
| ( module-type )
specification ::= val value-name : typexpr
| external value-name : typexpr = external-declaration
| type-definition
| exception constr-decl
| class-specification
| classtype-definition
| module module-name : module-type
| module module-name { ( module-name : module-type ) } :
module-type
| module type modtype-name
| module type modtype-name = module-type
| open module-path
| include modtype-path
mod-constraint ::= type [type-parameters] typeconstr = typexpr
| module module-path = extended-module-path
6.10.1 Simple module types
============================
The expression modtype-path is equivalent to the module type bound to the
name modtype-path. The expression ( module-type ) denotes the same type as
module-type.
6.10.2 Signatures
===================
Signatures are type specifications for structures. Signatures sig ... end are
collections of type specifications for value names, type names, exceptions,
module names and module type names. A structure will match a signature if the
structure provides definitions (implementations) for all the names specified in
the signature (and possibly more), and these definitions meet the type
requirements given in the signature.
For compatibility with Caml Light, an optional ;; is allowed after each
specification in a signature. The ;; has no semantic meaning.
Value specifications
--------------------
A specification of a value component in a signature is written val value-name
: typexpr, where value-name is the name of the value and typexpr its expected
type.
The form external value-name : typexpr = external-declaration is similar,
except that it requires in addition the name to be implemented as the external
function specified in external-declaration (see chapter 17).
Type specifications
-------------------
A specification of one or several type components in a signature is written
type typedef { and typedef } and consists of a sequence of mutually recursive
definitions of type names.
Each type definition in the signature specifies an optional type equation =
typexp and an optional type representation = constr-decl ... or = { label-decl
... }. The implementation of the type name in a matching structure must be
compatible with the type expression specified in the equation (if given), and
have the specified representation (if given). Conversely, users of that
signature will be able to rely on the type equation or type representation, if
given. More precisely, we have the following four situations:
Abstract type: no equation, no representation.
Names that are defined as abstract types in a signature can be implemented in
a matching structure by any kind of type definition (provided it has the
same number of type parameters). The exact implementation of the type will
be hidden to the users of the structure. In particular, if the type is
implemented as a variant type or record type, the associated constructors
and fields will not be accessible to the users; if the type is implemented
as an abbreviation, the type equality between the type name and the
right-hand side of the abbreviation will be hidden from the users of the
structure. Users of the structure consider that type as incompatible with
any other type: a fresh type has been generated.
Type abbreviation: an equation = typexp, no representation.
The type name must be implemented by a type compatible with typexp. All users
of the structure know that the type name is compatible with typexp.
New variant type or record type: no equation, a representation.
The type name must be implemented by a variant type or record type with
exactly the constructors or fields specified. All users of the structure
have access to the constructors or fields, and can use them to create or
inspect values of that type. However, users of the structure consider that
type as incompatible with any other type: a fresh type has been generated.
Re-exported variant type or record type: an equation, a representation.
This case combines the previous two: the representation of the type is made
visible to all users, and no fresh type is generated.
Exception specification
-----------------------
The specification exception constr-decl in a signature requires the matching
structure to provide an exception with the name and arguments specified in the
definition, and makes the exception available to all users of the structure.
Class specifications
--------------------
A specification of one or several classes in a signature is written class
class-spec { and class-spec } and consists of a sequence of mutually recursive
definitions of class names.
Class specifications are described more precisely in section 6.9.4.
Class type specifications
-------------------------
A specification of one or several classe types in a signature is written
class type classtype-def { and classtype-def } and consists of a sequence of
mutually recursive definitions of class type names. Class type specifications
are described more precisely in section 6.9.5.
Module specifications
---------------------
A specification of a module component in a signature is written module
module-name : module-type, where module-name is the name of the module
component and module-type its expected type. Modules can be nested arbitrarily;
in particular, functors can appear as components of structures and functor
types as components of signatures.
For specifying a module component that is a functor, one may write
module module-name ( name_1 : module-type_1 ) ... ( name_n : module-type_n
) : module-type
instead of
module module-name : functor ( name_1 : module-type_1 ) -> ... ->
module-type
Module type specifications
--------------------------
A module type component of a signature can be specified either as a manifest
module type or as an abstract module type.
An abstract module type specification module type modtype-name allows the
name modtype-name to be implemented by any module type in a matching signature,
but hides the implementation of the module type to all users of the signature.
A manifest module type specification module type modtype-name = module-type
requires the name modtype-name to be implemented by the module type module-type
in a matching signature, but makes the equality between modtype-name and
module-type apparent to all users of the signature.
Opening a module path
----------------------
The expression open module-path in a signature does not specify any
components. It simply affects the parsing of the following items of the
signature, allowing components of the module denoted by module-path to be
referred to by their simple names name instead of path accesses module-path .
name. The scope of the open stops at the end of the signature expression.
Including a signature
----------------------
The expression include modtype-path in a signature performs textual inclusion
of the components of the signature denoted by modtype-path. It behaves as if
the components of the included signature were copied at the location of the
include. The modtype-path argument must refer to a module type that is a
signature,
6.10.3 Functor types
======================
The module type expression functor ( module-name : module-type_1 ) ->
module-type_2 is the type of functors (functions from modules to modules) that
take as argument a module of type module-type_1 and return as result a module
of type module-type_2. The module type module-type_2 can use the name
module-name to refer to type components of the actual argument of the functor.
No restrictions are placed on the type of the functor argument; in particular,
a functor may take another functor as argument (``higher-order'' functor).
6.10.4 The with operator
==========================
Assuming module-type denotes a signature, the expression module-type with
mod-constraint { and mod-constraint } denotes the same signature where type
equations have been added to some of the type specifications, as described by
the constraints following the with keyword. The constraint type
[type-parameters] typeconstr = typexp adds the type equation = typexp to the
specification of the type component named typeconstr of the constrained
signature. The constraint module module-path = extended-module-path adds type
equations to all type components of the sub-structure denoted by module-path,
making them equivalent to the corresponding type components of the structure
denoted by extended-module-path.
For instance, if the module type name S is bound to the signature
<<
sig type t module M: (sig type u end) end
>>
then S with type t=int denotes the signature
<<
sig type t=int module M: (sig type u end) end
>>
and S with module M = N denotes the signature
<<
sig type t module M: (sig type u=N.u end) end
>>
A functor taking two arguments of type S that share their t component is
written
<<
functor (A: S) (B: S with type t = A.t) ...
>>
6.11 Module expressions (module implementations)
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Module expressions are the module-level equivalent of value expressions: they
evaluate to modules, thus providing implementations for the specifications
expressed in module types.
module-expr ::= module-path
| struct { definition [;;] } end
| functor ( module-name : module-type ) -> module-expr
| module-expr ( module-expr )
| ( module-expr )
| ( module-expr : module-type )
definition ::= let [rec] let-binding { and let-binding }
| external value-name : typexpr = external-declaration
| type-definition
| exception-definition
| class-definition
| classtype-definition
| module module-name { ( module-name : module-type ) } [ :
module-type ] = module-expr
| module type modtype-name = module-type
| open module-path
| include module-expr
6.11.1 Simple module expressions
==================================
The expression module-path evaluates to the module bound to the name
module-path.
The expression ( module-expr ) evaluates to the same module as module-expr.
The expression ( module-expr : module-type ) checks that the type of
module-expr is a subtype of module-type, that is, that all components specified
in module-type are implemented in module-expr, and their implementation meets
the requirements given in module-type. In other terms, it checks that the
implementation module-expr meets the type specification module-type. The whole
expression evaluates to the same module as module-expr, except that all
components not specified in module-type are hidden and can no longer be
accessed.
6.11.2 Structures
===================
Structures struct ... end are collections of definitions for value names,
type names, exceptions, module names and module type names. The definitions are
evaluated in the order in which they appear in the structure. The scope of the
bindings performed by the definitions extend to the end of the structure. As a
consequence, a definition may refer to names bound by earlier definitions in
the same structure.
For compatibility with toplevel phrases (chapter 9) and with Caml Light, an
optional ;; is allowed after each definition in a structure. The ;; has no
semantic meaning. Also for compatibility, ;; expr is allowed as a component of
a structure, meaning let _ = expr, i.e. evaluate expr for its side-effects.
Value definitions
-----------------
A value definition let [rec] let-binding { and let-binding } bind value names
in the same way as a let ... in ... expression (see section 6.7.1). The value
names appearing in the left-hand sides of the bindings are bound to the
corresponding values in the right-hand sides.
A value definition external value-name : typexpr = external-declaration
implements value-name as the external function specified in
external-declaration (see chapter 17).
Type definitions
----------------
A definition of one or several type components is written type typedef { and
typedef } and consists of a sequence of mutually recursive definitions of type
names.
Exception definitions
---------------------
Exceptions are defined with the syntax exception constr-decl or exception
constr-name = constr.
Class definitions
-----------------
A definition of one or several classes is written class class-binding { and
class-binding } and consists of a sequence of mutually recursive definitions of
class names. Class definitions are described more precisely in section 6.9.3.
Class type definitions
----------------------
A definition of one or several classes is written class type classtype-def {
and classtype-def } and consists of a sequence of mutually recursive
definitions of class type names. Class type definitions are described more
precisely in section 6.9.5.
Module definitions
------------------
The basic form for defining a module component is module module-name =
module-expr, which evaluates module-expr and binds the result to the name
module-name.
One can write
module module-name : module-type = module-expr
instead of
module module-name = ( module-expr : module-type ).
Another derived form is
module module-name ( name_1 : module-type_1 ) ... ( name_n : module-type_n
) = module-expr
which is equivalent to
module module-name = functor ( name_1 : module-type_1 ) -> ... ->
module-expr
Module type definitions
-----------------------
A definition for a module type is written module type modtype-name =
module-type. It binds the name modtype-name to the module type denoted by the
expression module-type.
Opening a module path
---------------------
The expression open module-path in a structure does not define any components
nor perform any bindings. It simply affects the parsing of the following items
of the structure, allowing components of the module denoted by module-path to
be referred to by their simple names name instead of path accesses module-path
. name. The scope of the open stops at the end of the structure expression.
Including the components of another structure
---------------------------------------------
The expression include module-expr in a structure re-exports in the current
structure all definitions of the structure denoted by module-expr. For
instance, if the identifier S is bound to the module
<<
struct type t = int let x = 2 end
>>
the module expression
<<
struct include S let y = (x + 1 : t) end
>>
is equivalent to the module expression
<<
struct type t = int let x = 2 let y = (x + 1 : t) end
>>
The difference between open and include is that open simply provides short
names for the components of the opened structure, without defining any
components of the current structure, while include also adds definitions for
the components of the included structure.
6.11.3 Functors
=================
Functor definition
------------------
The expression functor ( module-name : module-type ) -> module-expr evaluates
to a functor that takes as argument modules of the type module-type_1, binds
module-name to these modules, evaluates module-expr in the extended
environment, and returns the resulting modules as results. No restrictions are
placed on the type of the functor argument; in particular, a functor may take
another functor as argument (``higher-order'' functor).
Functor application
-------------------
The expression module-expr_1 ( module-expr_2 ) evaluates module-expr_1 to a
functor and module-expr_2 to a module, and applies the former to the latter.
The type of module-expr_2 must match the type expected for the arguments of the
functor module-expr_1.
6.12 Compilation units
*=*=*=*=*=*=*=*=*=*=*=*=
unit-interface ::= { specification [;;] }
unit-implementation ::= { definition [;;] }
Compilation units bridge the module system and the separate compilation
system. A compilation unit is composed of two parts: an interface and an
implementation. The interface contains a sequence of specifications, just as
the inside of a sig ... end signature expression. The implementation contains a
sequence of definitions, just as the inside of a struct ... end module
expression. A compilation unit also has a name unit-name, derived from the
names of the files containing the interface and the implementation (see chapter
8 for more details). A compilation unit behaves roughly as the module
definition
module unit-name : sig unit-interface end = struct unit-implementation end
A compilation unit can refer to other compilation units by their names, as if
they were regular modules. For instance, if U is a compilation unit that
defines a type t, other compilation units can refer to that type under the name
U.t; they can also refer to U as a whole structure. Except for names of other
compilation units, a unit interface or unit implementation must not have any
other free variables. In other terms, the type-checking and compilation of an
interface or implementation proceeds in the initial environment
name_1 : sig interface_1 end ... name_n : sig interface_n end
where name_1 ... name_N are the names of the other compilation units
available in the search path (see chapter 8 for more details) and interface_1
... interface_n are their respective interfaces.
Chapter 7 Language extensions
*********************************
This chapter describes the language features that are implemented in
Objective Caml, but not described in the Objective Caml reference manual. In
contrast with the fairly stable kernel language that is described in the
reference manual, the extensions presented here are still experimental, and may
be removed or changed in the future.
7.1 Streams and stream parsers
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Objective Caml comprises a library type for streams (possibly infinite
sequences of elements, that are evaluated on demand), and associated stream
expressions, to build streams, and stream patterns, to destructure streams.
Streams and stream patterns provide a natural approach to the writing of
recursive-descent parsers.
Streams are presented by the following extensions to the syntactic classes of
expressions:
expr ::= ...
| [< >]
| [< stream-component { ; stream-component } >]
| parser [pattern] stream-matching
| match expr with parser [pattern] stream-matching
stream-component ::= ' expr
| expr
stream-matching ::= stream-pattern [pattern] -> expr { | stream-pattern
[pattern] -> expr }
stream-pattern ::= [< >]
| [< stream-pat-comp { ; stream-pat-comp [ ?? expr ] }>]
stream-pat-comp ::= ' pattern [ when expr ]
| pattern = expr
| ident
Stream expressions are bracketed by `[<' and `>]'. They represent the
concatenation of their components. The component ' expr represents the
one-element stream whose element is the value of expr. The component expr
represents a sub-stream. For instance, if both s and t are streams of integers,
then `[<'1; s; t; '2>]' is a stream of integers containing the element 1, then
the elements of s, then those of t, and finally 2. The empty stream is denoted
by `[< >]'.
Unlike any other kind of expressions in the language, stream expressions are
submitted to lazy evaluation: the components are not evaluated when the stream
is built, but only when they are accessed during stream matching. The
components are evaluated once, the first time they are accessed; the following
accesses reuse the value computed the first time.
Stream patterns, also bracketed by `[<' and `>]', describe initial segments
of streams. In particular, the stream pattern `[< >]' matches all streams.
Stream pattern components are matched against the corresponding elements of a
stream. The component ' pattern matches the corresponding stream element
against the pattern; if followed by when, the match is accepted only if the
result of the guard expression is true. The component pattern = expr applies
the function denoted by expr to the current stream, then matches the result of
the function against pattern. Finally, the component ident simply binds the
identifier to the stream being matched.
Stream matching proceeds destructively: once a component has been matched, it
is discarded from the stream (by in-place modification).
Stream matching proceeds in two steps: first, a pattern is selected by
matching the stream against the first components of the stream patterns; then,
the following components of the selected pattern are checked against the
stream. If the following components do not match, the exception Stream.Error is
raised. There is no backtracking here: stream matching commits to the pattern
selected according to the first element. If none of the first components of the
stream patterns match, the exception Stream.Failure is raised. The
Stream.Failure exception causes the next alternative to be tried, if it occurs
during the matching of the first element of a stream, before matching has
committed to one pattern.
The streams hold the count of their elements discarded. The optional pattern
before the first stream pattern is bound to the stream count before the
matching. The one after each stream pattern (optional, too) is bound to the
stream count after the matching.
The exception Stream.Error has a string parameter coming from the optional ??
expr after the stream pattern components (its default is the empty string).
This expression is evaluated only in case of error.
See Functional programming using Caml Light for a more gentle introductions
to streams, and for some examples of their use in writing parsers. A more
formal presentation of streams, and a discussion of alternate semantics, can be
found in Parsers in ML by Michel Mauny and Daniel de Rauglaudre, in the
proceedings of the 1992 ACM conference on Lisp and Functional Programming.
7.2 Range patterns
*=*=*=*=*=*=*=*=*=*=
In patterns, Objective Caml recognizes the form ' c ' .. ' d ' (two character
literals separated by ..) as shorthand for the pattern
' c ' | ' c_1 ' | ' c_2 ' | ... | ' c_n ' | ' d '
where c_1, c_2, ..., c_n are the characters that occur between c and d in
the ASCII character set. For instance, the pattern '0'..'9' matches all
characters that are digits.
7.3 Assertion checking
*=*=*=*=*=*=*=*=*=*=*=*=
Objective Caml supports the assert construct to check debugging assertions.
The expression assert expr evaluates the expression expr and returns () if expr
evaluates to true. Otherwise, the exception Assert_failure is raised with the
source file name and the location of expr as arguments. Assertion checking can
be turned off with the -noassert compiler option.
As a special case, assert false is reduced to raise (Assert_failure ...),
which is polymorphic (and is not turned off by the -noassert option).
7.4 Deferred computations
*=*=*=*=*=*=*=*=*=*=*=*=*=*
The expression lazy expr returns a value v of type Lazy.t that encapsulates
the computation of expr. The argument expr is not evaluated at this point in
the program. Instead, its evaluation will be performed the first time
Lazy.force is applied to the value v, returning the actual value of expr.
Subsequent applications of Lazy.force to v do not evaluate expr again.
The expression lazy expr is equivalent to ref(Lazy.Delayed(fun () -> expr)).
For more information, see the description of module Lazy in the standard
library (section 19.14).
7.5 Record copy with update
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
The expression { expr with lbl_1 = expr_1 ; ... ; lbl_n = expr_n } builds a
fresh record with fields lbl_1 ... lbl_n equal to expr_1 ... expr_n, and all
other fields having the same value as in the record expr. In other terms, it
returns a shallow copy of the record expr, except for the fields lbl_1 ...
lbl_n, which are initialized to expr_1 ... expr_n. For example:
<<
type point = { x : float; y : float; z : float }
let proj p = { p with x = 0.0 }
let proj p = { x = 0.0; y = p.y; z = p.z }
>>
The two definitions of proj above are equivalent.
7.6 Local modules
*=*=*=*=*=*=*=*=*=*
The expression let module module-name = module-expr in expr locally binds the
module expression module-expr to the identifier module-name during the
evaluation of the expression expr. It then returns the value of expr. For
example:
<<
let remove_duplicates comparison_fun string_list =
let module StringSet =
Set.Make(struct type t = string
let compare = comparison_fun end) in
StringSet.elements
(List.fold_right StringSet.add string_list StringSet.empty)
>>
Part: III
*********
The Objective Caml tools
*************************
Chapter 8 Batch compilation (ocamlc)
****************************************
This chapter describes the Objective Caml batch compiler ocamlc, which
compiles Caml source files to bytecode object files and link these object files
to produce standalone bytecode executable files. These executable files are
then run by the bytecode interpreter ocamlrun.
8.1 Overview of the compiler
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
The ocamlc command has a command-line interface similar to the one of most C
compilers. It accepts several types of arguments:
- Arguments ending in .mli are taken to be source files for compilation unit
interfaces. Interfaces specify the names exported by compilation units: they
declare value names with their types, define public data types, declare
abstract data types, and so on. From the file x.mli, the ocamlc compiler
produces a compiled interface in the file x.cmi.
- Arguments ending in .ml are taken to be source files for compilation unit
implementations. Implementations provide definitions for the names exported
by the unit, and also contain expressions to be evaluated for their
side-effects. From the file x.ml, the ocamlc compiler produces compiled
object bytecode in the file x.cmo.
If the interface file x.mli exists, the implementation x.ml is checked against
the corresponding compiled interface x.cmi, which is assumed to exist. If no
interface x.mli is provided, the compilation of x.ml produces a compiled
interface file x.cmi in addition to the compiled object code file x.cmo. The
file x.cmi produced corresponds to an interface that exports everything that
is defined in the implementation x.ml.
- Arguments ending in .cmo are taken to be compiled object bytecode. These
files are linked together, along with the object files obtained by compiling
.ml arguments (if any), and the Caml Light standard library, to produce a
standalone executable program. The order in which .cmo and .ml arguments are
presented on the command line is relevant: compilation units are initialized
in that order at run-time, and it is a link-time error to use a component of
a unit before having initialized it. Hence, a given x.cmo file must come
before all .cmo files that refer to the unit x.
- Arguments ending in .cma are taken to be libraries of object bytecode. A
library of object bytecode packs in a single file a set of object bytecode
files (.cmo files). Libraries are built with ocamlc -a (see the description
of the -a option below). The object files contained in the library are
linked as regular .cmo files (see above), in the order specified when the
.cma file was built. The only difference is that if an object file contained
in a library is not referenced anywhere in the program, then it is not
linked in.
- Arguments ending in .c are passed to the C compiler, which generates a .o
object file. This object file is linked with the program if the -custom flag
is set (see the description of -custom below).
- Arguments ending in .o or .a are assumed to be C object files and libraries.
They are passed to the C linker when linking in -custom mode (see the
description of -custom below).
The output of the linking phase is a file containing compiled bytecode that
can be executed by the Objective Caml bytecode interpreter: the command named
ocamlrun. If caml.out is the name of the file produced by the linking phase,
the command
<<
ocamlrun caml.out arg_1 arg_2 ... arg_n
>>
executes the compiled code contained in caml.out, passing it as arguments
the character strings arg_1 to arg_n. (See chapter 10 for more details.)
On most Unix systems, the file produced by the linking phase can be run
directly, as in:
<<
./caml.out arg_1 arg_2 ... arg_n
>>
The produced file has the executable bit set, and it manages to launch the
bytecode interpreter by itself.
8.2 Options
*=*=*=*=*=*=*
The following command-line options are recognized by ocamlc.
-a Build a library (.cma file) with the object files (.cmo files) given on
the command line, instead of linking them into an executable file. The name
of the library can be set with the -o option. The default name is
library.cma.
If -custom, -cclib or -ccopt options are passed on the command line, these
options are stored in the resulting .cma library. Then, linking with this
library automatically adds back the -custom, -cclib and -ccopt options as if
they had been provided on the command line, unless the -noautolink option is
given.
-c Compile only. Suppress the linking phase of the compilation. Source code
files are turned into compiled files, but no executable file is produced.
This option is useful to compile modules separately.
-cc ccomp Use ccomp as the C linker called by ocamlc -custom and as the C
compiler for compiling .c source files.
-cclib -llibname Pass the -llibname option to the C linker when linking in
``custom runtime'' mode (see the -custom option). This causes the given C
library to be linked with the program.
-ccopt option Pass the given option to the C compiler and linker, when
linking in ``custom runtime'' mode (see the -custom option). For instance,
-ccopt -Ldir causes the C linker to search for C libraries in directory dir.
-custom Link in ``custom runtime'' mode. In the default linking mode, the
linker produces bytecode that is intended to be executed with the shared
runtime system, ocamlrun. In the custom runtime mode, the linker produces an
output file that contains both the runtime system and the bytecode for the
program. The resulting file is larger, but it can be executed directly, even
if the ocamlrun command is not installed. Moreover, the ``custom runtime''
mode enables linking Caml code with user-defined C functions, as described
in chapter 17. Unix:
Never use the strip command on executables produced by
ocamlc -custom. This would remove the bytecode part of the
executable.
-g Add debugging information while compiling and linking. This option is
required in order to be able to debug the program with ocamldebug (see
chapter 15).
-i Cause the compiler to print all defined names (with their inferred types
or their definitions) when compiling an implementation (.ml file). This can
be useful to check the types inferred by the compiler. Also, since the
output follows the syntax of interfaces, it can help in writing an explicit
interface (.mli file) for a file: just redirect the standard output of the
compiler to a .mli file, and edit that file to remove all declarations of
unexported names.
-I directory Add the given directory to the list of directories searched for
compiled interface files (.cmi), compiled object code files (.cmo), and
libraries (.cma). By default, the current directory is searched first, then
the standard library directory. Directories added with -I are searched after
the current directory, in the order in which they were given on the command
line, but before the standard library directory.
If the given directory starts with +, it is taken relative to the standard
library directory. For instance, -I +labltk adds the subdirectory labltk of
the standard library to the search path.
-impl filename Compile the file filename as an implementation file, even if
its extension is not .ml.
-intf filename Compile the file filename as an interface file, even if its
extension is not .mli.
-labels Switch to the commuting label mode of compilation, meaning that
labeling rules are applied strictly, and commutation between labeled
arguments is allowed. (See section 2.1.4.) This mode cannot be used to
compile a program written in the default classic style, but modules written
in the two styles can be mixed in the same application.
-linkall Force all modules contained in libraries to be linked in. If this
flag is not given, unreferenced modules are not linked in. When building a
library (-a flag), setting the -linkall flag forces all subsequent links of
programs involving that library to link all the modules contained in the
library.
-make-runtime Build a custom runtime system (in the file specified by option
-o) incorporating the C object files and libraries given on the command
line. This custom runtime system can be used later to execute bytecode
executables produced with the ocamlc -use-runtime runtime-name option. See
section 17.1.4 for more information.
-noassert Turn assertion checking off: assertions are not compiled. This flag
has no effect when linking already compiled files.
-noautolink When linking .cma libraries, ignore -custom, -cclib and -ccopt
options potentially contained in the libraries (if these options were given
when building the libraries). This can be useful if a library contains
incorrect specifications of C libraries or C options; in this case, during
linking, set -noautolink and pass the correct C libraries and options on the
command line.
-o exec-file Specify the name of the output file produced by the linker. The
default output name is a.out, in keeping with the Unix tradition. If the -a
option is given, specify the name of the library produced. If the
-output-obj option is given, specify the name of the output file produced.
-output-obj Cause the linker to produce a C object file instead of a bytecode
executable file. This is useful to wrap Caml code as a C library, callable
from any C program. See chapter 17, section 17.7.5. The name of the output
object file is camlprog.o by default; it can be set with the -o option.
-pp command Cause the compiler to call the given command as a preprocessor
for each source file. The output of command is redirected to an intermediate
file, which is compiled. If there are no compilation errors, the
intermediate file is deleted afterwards. The name of this file is built from
the basename of the source file with the extension .ppi for an interface
(.mli) file and .ppo for an implementation (.ml) file.
-rectypes Allow arbitrary recursive types during type-checking. By default,
only recursive types where the recursion goes through an object type are
supported.
-thread Compile or link multithreaded programs, in combination with the
threads library described in chapter 23. What this option actually does is
select a special, thread-safe version of the standard library.
-unsafe Turn bound checking off on array and string accesses (the v.(i) and
s.[i] constructs). Programs compiled with -unsafe are therefore slightly
faster, but unsafe: anything can happen if the program accesses an array or
string outside of its bounds.
-use-runtime runtime-name Generate a bytecode executable file that can be
executed on the custom runtime system runtime-name, built earlier with
ocamlc -make-runtime runtime-name. See section 17.1.4 for more information.
-v Print the version number of the compiler.
-w warning-list Enable or disable warnings according to the argument
warning-list. The argument is a string of one or several characters, with
the following meaning for each character:
A/a enable/disable all warnings
F/f enable/disable warnings for partially applied functions (i.e. f x;
expr where the application f x has a function type).
M/m enable/disable warnings for overriden methods.
P/p enable/disable warnings for partial matches (missing cases in pattern
matchings).
S/s enable/disable warnings for statements that do not have type unit
(e.g. expr1; expr2 when expr1 does not have type unit).
U/u enable/disable warnings for unused (redundant) match cases.
V/v enable/disable warnings for hidden instance variables.
X/x enable/disable all other warnings.
The default setting is -w A (all warnings enabled).
-warn-error warning-list Turn the warnings indicated in the argument
warning-list into errors. The compiler will stop on an error as soon as one
of these warnings is emitted, instead of going on. The warning-list is a
string of one or several characters, with the same meaning as for the -w
option: an uppercase character turns the corresponding warning into an
error, a lowercase character leaves it as a warning. The default setting is
-warn-error a (all warnings are not treated as errors).
-where Print the location of the standard library.
8.3 Modules and the file system
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This short section is intended to clarify the relationship between the names
of the modules corresponding to compilation units and the names of the files
that contain their compiled interface and compiled implementation.
The compiler always derives the module name by taking the capitalized base
name of the source file (.ml or .mli file). That is, it strips the leading
directory name, if any, as well as the .ml or .mli suffix; then, it set the
first letter to uppercase, in order to comply with the requirement that module
names must be capitalized. For instance, compiling the file mylib/misc.ml
provides an implementation for the module named Misc. Other compilation units
may refer to components defined in mylib/misc.ml under the names Misc.name;
they can also do open Misc, then use unqualified names name.
The .cmi and .cmo files produced by the compiler have the same base name as
the source file. Hence, the compiled files always have their base name equal
(modulo capitalization of the first letter) to the name of the module they
describe (for .cmi files) or implement (for .cmo files).
When the compiler encounters a reference to a free module identifier Mod, it
looks in the search path for a file mod.cmi (note lowercasing of first letter)
and loads the compiled interface contained in that file. As a consequence,
renaming .cmi files is not advised: the name of a .cmi file must always
correspond to the name of the compilation unit it implements. It is admissible
to move them to another directory, if their base name is preserved, and the
correct -I options are given to the compiler. The compiler will flag an error
if it loads a .cmi file that has been renamed.
Compiled bytecode files (.cmo files), on the other hand, can be freely
renamed once created. That's because the linker never attempts to find by
itself the .cmo file that implements a module with a given name: it relies
instead on the user providing the list of .cmo files by hand.
8.4 Common errors
*=*=*=*=*=*=*=*=*=*
This section describes and explains the most frequently encountered error
messages.
Cannot find file filename The named file could not be found in the current
directory, nor in the directories of the search path. The filename is either
a compiled interface file (.cmi file), or a compiled bytecode file (.cmo
file). If filename has the format mod.cmi, this means you are trying to
compile a file that references identifiers from module mod, but you have not
yet compiled an interface for module mod. Fix: compile mod.mli or mod.ml
first, to create the compiled interface mod.cmi.
If filename has the format mod.cmo, this means you are trying to link a
bytecode object file that does not exist yet. Fix: compile mod.ml first.
If your program spans several directories, this error can also appear because
you haven't specified the directories to look into. Fix: add the correct -I
options to the command line.
Corrupted compiled interface filename The compiler produces this error when
it tries to read a compiled interface file (.cmi file) that has the wrong
structure. This means something went wrong when this .cmi file was written:
the disk was full, the compiler was interrupted in the middle of the file
creation, and so on. This error can also appear if a .cmi file is modified
after its creation by the compiler. Fix: remove the corrupted .cmi file, and
rebuild it.
This expression has type t_1, but is used with type t_2 This is by far the
most common type error in programs. Type t_1 is the type inferred for the
expression (the part of the program that is displayed in the error message),
by looking at the expression itself. Type t_2 is the type expected by the
context of the expression; it is deduced by looking at how the value of this
expression is used in the rest of the program. If the two types t_1 and t_2
are not compatible, then the error above is produced.
In some cases, it is hard to understand why the two types t_1 and t_2 are
incompatible. For instance, the compiler can report that ``expression of
type foo cannot be used with type foo'', and it really seems that the two
types foo are compatible. This is not always true. Two type constructors can
have the same name, but actually represent different types. This can happen
if a type constructor is redefined. Example:
<<
type foo = A | B
let f = function A -> 0 | B -> 1
type foo = C | D
f C
>>
This result in the error message ``expression C of type foo cannot be used
with type foo''.
The type of this expression, t, contains type variables that cannot be
generalized Type variables ('a, 'b, ...) in a type t can be in either of
two states: generalized (which means that the type t is valid for all
possible instantiations of the variables) and not generalized (which means
that the type t is valid only for one instantiation of the variables). In a
let binding let name = expr, the type-checker normally generalizes as many
type variables as possible in the type of expr. However, this leads to
unsoundness (a well-typed program can crash) in conjunction with polymorphic
mutable data structures. To avoid this, generalization is performed at let
bindings only if the bound expression expr belongs to the class of
``syntactic values'', which includes constants, identifiers, functions,
tuples of syntactic values, etc. In all other cases (for instance, expr is a
function application), a polymorphic mutable could have been created and
generalization is therefore turned off.
Non-generalized type variables in a type cause no difficulties inside a given
structure or compilation unit (the contents of a .ml file, or an interactive
session), but they cannot be allowed inside signatures nor in compiled
interfaces (.cmi file), because they could be used inconsistently later.
Therefore, the compiler flags an error when a structure or compilation unit
defines a value name whose type contains non-generalized type variables.
There are two ways to fix this error:
- Add a type constraint or a .mli file to give a monomorphic type (without
type variables) to name. For instance, instead of writing
<<
let sort_int_list = Sort.list (<)
(* inferred type 'a list -> 'a list, with 'a not generalized *)
>>
write
<<
let sort_int_list = (Sort.list (<) : int list -> int list);;
>>
- If you really need name to have a polymorphic type, turn its defining
expression into a function by adding an extra parameter. For instance,
instead of writing
<<
let map_length = List.map Array.length
(* inferred type 'a array list -> int list, with 'a not generalized
*)
>>
write
<<
let map_length lv = List.map Array.length lv
>>
Reference to undefined global mod This error appears when trying to link an
incomplete or incorrectly ordered set of files. Either you have forgotten to
provide an implementation for the compilation unit named mod on the command
line (typically, the file named mod.cmo, or a library containing that file).
Fix: add the missing .ml or .cmo file to the command line. Or, you have
provided an implementation for the module named mod, but it comes too late
on the command line: the implementation of mod must come before all bytecode
object files that reference mod. Fix: change the order of .ml and .cmo files
on the command line.
Of course, you will always encounter this error if you have mutually recursive
functions across modules. That is, function Mod1.f calls function Mod2.g,
and function Mod2.g calls function Mod1.f. In this case, no matter what
permutations you perform on the command line, the program will be rejected
at link-time. Fixes:
- Put f and g in the same module.
- Parameterize one function by the other. That is, instead of having
<<
mod1.ml: let f x = ... Mod2.g ...
mod2.ml: let g y = ... Mod1.f ...
>>
define
<<
mod1.ml: let f g x = ... g ...
mod2.ml: let rec g y = ... Mod1.f g ...
>>
and link mod1.cmo before mod2.cmo.
- Use a reference to hold one of the two functions, as in :
<<
mod1.ml: let forward_g =
ref((fun x -> failwith "forward_g") : <type>)
let f x = ... !forward_g ...
mod2.ml: let g y = ... Mod1.f ...
let _ = Mod1.forward_g := g
>>
This will not work if g is a polymorphic function, however.
The external function f is not available This error appears when trying to
link code that calls external functions written in C in ``default runtime''
mode. As explained in chapter 17, such code must be linked in ``custom
runtime'' mode. Fix: add the -custom option, as well as the C libraries and
C object files that implement the required external functions.
Chapter 9 The toplevel system (ocaml)
*****************************************
This chapter describes the toplevel system for Objective Caml, that permits
interactive use of the Objective Caml system through a read-eval-print loop. In
this mode, the system repeatedly reads Caml phrases from the input, then
typechecks, compile and evaluate them, then prints the inferred type and result
value, if any. The system prints a # (sharp) prompt before reading each phrase.
Input to the toplevel can span several lines. It is terminated by ;; (a
double-semicolon). The toplevel input consists in one or several toplevel
phrases, with the following syntax:
toplevel-input ::= { toplevel-phrase } ;;
toplevel-phrase ::= definition
| expr
| # ident directive-argument
definition ::= let [rec] let-binding { and let-binding }
| external value-name : typexpr = external-declaration
| type-definition
| exception-definition
| module module-name [ : module-type ] = module-expr
| module type modtype-name = module-type
| open module-path
directive-argument ::= nothing
| string-literal
| integer-literal
| value-path
A phrase can consist of a definition, similar to those found in
implementations of compilation units or in struct ... end module expressions.
The definition can bind value names, type names, an exception, a module name,
or a module type name. The toplevel system performs the bindings, then prints
the types and values (if any) for the names thus defined.
A phrase may also consist in a open directive (see section 6.11), or a value
expression (section 6.7). Expressions are simply evaluated, without performing
any bindings, and the value of the expression is printed.
Finally, a phrase can also consist in a toplevel directive, starting with #
(the sharp sign). These directives control the behavior of the toplevel; they
are listed below in section 9.2.
Unix:
The toplevel system is started by the command ocaml, as
follows:
<<
ocaml options # interactive mode
ocaml options scriptfile # script mode
>>
If no filename is given on the command line, the toplevel
system enters interactive mode: phrases are read on standard
input, results are printed on standard output, errors on
standard error. End-of-file on standard input terminates ocaml
(see also the #quit directive in section 9.2).
On start-up (before the first phrase is read), if the file
.ocamlinit exists in the current directory, its contents are
read as a sequence of Objective Caml phrases and executed as per
the #use directive described in section 9.2. The evaluation
outcode for each phrase are not displayed.
The toplevel system does not perform line editing, but it can
easily be used in conjunction with an external line editor such
as fep; just run fep -emacs ocaml or fep -vi ocaml. Another
option is to use ocaml under Gnu Emacs, which gives the full
editing power of Emacs (see the subdirectory emacs of the
Objective Caml distribution).
At any point, the parsing, compilation or evaluation of the
current phrase can be interrupted by pressing ctrl-C (or, more
precisely, by sending the sigintr signal to the ocaml process).
The toplevel then immediately returns to the # prompt.
If a filename is given on the command-line to ocaml, the
toplevel system enters script mode: the contents of the file are
read as a sequence of Objective Caml phrases and executed, as
per the #use directive (section 9.2). The outcome of the
evaluation is not printed. On reaching the end of file, the
ocaml command exits immediately. No commands are read from
standard input. Sys.argv is transformed, ignoring all Objective
Caml parameters, and starting with the script file name in
Sys.argv.(0).
In script mode, the first line of the script is ignored if it
starts with #!. Thus, it is theoretically possible to make the
script itself executable and put as first line
#!/usr/local/bin/ocaml, thus calling the toplevel system
automatically when the script is run. However, ocaml itself is a
#! script on most installations of Objective Caml, and Unix
kernels usually do not handle nested #! scripts.
Windows:
In addition to the text-only command ocaml.exe, which works
exactly as under Unix (see above), a graphical user interface
for the toplevel is available under the name ocamlwin.exe. It
should be launched from the Windows file manager or program
manager.
The ``Terminal'' windows is split in two panes. Phrases are
entered and edited in the bottom pane. The top pane displays a
copy of the input phrases as they are processed by the Caml
Light toplevel, interspersed with the toplevel responses. The
``Return'' key sends the contents of the bottom pane to the Caml
Light toplevel. The ``Enter'' key inserts a newline without
sending the contents of the Input window. (This can be
configured with the ``Preferences'' menu item.)
The contents of the input window can be edited at all times,
with the standard Windows interface. An history of previously
entered phrases is maintained and displayed in a separate
window.
To quit the Camlwin application, either select ``Quit'' from the
``File'' menu, or use the quit function described below.
At any point, the parsing, compilation or evaluation of the
current phrase can be interrupted by selecting the ``Interrupt
Caml Light'' menu item. This goes back to the # prompt.
9.1 Options
*=*=*=*=*=*=*
The following command-line options are recognized by the ocaml command.
-I directory Add the given directory to the list of directories searched for
source and compiled files. By default, the current directory is searched
first, then the standard library directory. Directories added with -I are
searched after the current directory, in the order in which they were given
on the command line, but before the standard library directory.
If the given directory starts with +, it is taken relative to the standard
library directory. For instance, -I +labltk adds the subdirectory labltk of
the standard library to the search path.
Directories can also be added to the search path once the toplevel is running
with the #directory directive (section 9.2).
-labels Switch to the commuting label mode of compilation, meaning that
labeling rules are applied strictly, and commutation between arguments is
allowed. (See section 2.1.4.)
-rectypes Allow arbitrary recursive types during type-checking. By default,
only recursive types where the recursion goes through an object type are
supported.
-unsafe See the corresponding option for ocamlc, chapter 8. Turn bound
checking off on array and string accesses (the v.(i) and s.[i] constructs).
Programs compiled with -unsafe are therefore slightly faster, but unsafe:
anything can happen if the program accesses an array or string outside of
its bounds.
-w warning-list Enable or disable warnings according to the argument
warning-list.
Unix:
The following environment variables are also consulted:
LC_CTYPE If set to iso_8859_1, accented characters (from the
ISO Latin-1 character set) in string and character literals
are printed as is; otherwise, they are printed as decimal
escape sequences (\ddd).
TERM When printing error messages, the toplevel system
attempts to underline visually the location of the error. It
consults the TERM variable to determines the type of output
terminal and look up its capabilities in the terminal
database.
9.2 Toplevel directives
*=*=*=*=*=*=*=*=*=*=*=*=*
The following directives control the toplevel behavior, load files in memory,
and trace program execution.
Note: all directives start with a # (sharp) symbol. This # must be typed
before the directive, and must not be confused with the # prompt displayed by
the interactive loop. For instance, typing #quit;; will exit the toplevel loop,
but typing quit;; will result in an ``unbound value quit'' error.
#quit;; Exit the toplevel loop and terminate the ocaml command.
#labels bool;; Switch to commuting label style if argument is true, or back
to classic (non-commuting) style if argument is false. (See section
2.1.4.)
#warnings "warning-list";; Enable or disable warnings according to the
argument.
#directory "dir-name";; Add the given directory to the list of directories
searched for source and compiled files.
#cd "dir-name";; Change the current working directory.
#load "file-name";; Load in memory a bytecode object file (.cmo file)
produced by the batch compiler ocamlc.
#use "file-name";; Read, compile and execute source phrases from the given
file. This is textual inclusion: phrases are processed just as if they were
typed on standard input. The reading of the file stops at the first error
encountered.
#install_printer printer-name;; This directive registers the function named
printer-name (a value path) as a printer for objects whose types match the
argument type of the function. That is, the toplevel loop will call
printer-name when it has such an object to print. The printing function
printer-name must use the Format library module to produce its output,
otherwise its output will not be correctly located in the values printed by
the toplevel loop.
#remove_printer printer-name;; Remove the named function from the table of
toplevel printers.
#trace function-name;; After executing this directive, all calls to the
function named function-name will be ``traced''. That is, the argument and
the result are displayed for each call, as well as the exceptions escaping
out of the function, raised either by the function itself or by another
function it calls. If the function is curried, each argument is printed as
it is passed to the function.
#untrace function-name;; Stop tracing the given function.
#untrace_all;; Stop tracing all functions traced so far.
#print_depth n;; Limit the printing of values to a maximal depth of n. The
parts of values whose depth exceeds n are printed as ... (ellipsis).
#print_length n;; Limit the number of value nodes printed to at most n.
Remaining parts of values are printed as ... (ellipsis).
9.3 The toplevel and the module system
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Toplevel phrases can refer to identifiers defined in compilation units with
the same mechanisms as for separately compiled units: either by using qualified
names (Modulename.localname), or by using the open construct and unqualified
names (see section 6.3).
However, before referencing another compilation unit, an implementation of
that unit must be present in memory. At start-up, the toplevel system contains
implementations for all the modules in the the standard library.
Implementations for user modules can be entered with the #load directive
described above. Referencing a unit for which no implementation has been
provided results in the error ``Reference to undefined global `...' ''.
Note that entering open mod merely accesses the compiled interface (.cmi
file) for mod, but does not load the implementation of mod, and does not cause
any error if no implementation of mod has been loaded. The error ``reference
to undefined global mod'' will occur only when executing a value or module
definition that refers to mod.
9.4 Common errors
*=*=*=*=*=*=*=*=*=*
This section describes and explains the most frequently encountered error
messages.
Cannot find file filename The named file could not be found in the current
directory, nor in the directories of the search path.
If filename has the format mod.cmi, this means you have referenced the
compilation unit mod, but its compiled interface could not be found. Fix:
compile mod.mli or mod.ml first, to create the compiled interface mod.cmi.
If filename has the format mod.cmo, this means you are trying to load with
#load a bytecode object file that does not exist yet. Fix: compile mod.ml
first.
If your program spans several directories, this error can also appear because
you haven't specified the directories to look into. Fix: use the #directory
directive to add the correct directories to the search path.
This expression has type t_1, but is used with type t_2 See section 8.4.
Reference to undefined global mod You have neglected to load in memory an
implementation for a module with #load. See section 9.3 above.
9.5 Building custom toplevel systems: ocamlmktop
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
The ocamlmktop command builds Objective Caml toplevels that contain user code
preloaded at start-up.
The ocamlmktop command takes as argument a set of .cmo and .cma files, and
links them with the object files that implement the Objective Caml toplevel.
The typical use is:
<<
ocamlmktop -o mytoplevel foo.cmo bar.cmo gee.cmo
>>
This creates the bytecode file mytoplevel, containing the Objective Caml
toplevel system, plus the code from the three .cmo files. This toplevel is
directly executable and is started by:
<<
./mytoplevel
>>
This enters a regular toplevel loop, except that the code from foo.cmo,
bar.cmo and gee.cmo is already loaded in memory, just as if you had typed:
<<
#load "foo.cmo";;
#load "bar.cmo";;
#load "gee.cmo";;
>>
on entrance to the toplevel. The modules Foo, Bar and Gee are not opened,
though; you still have to do
<<
open Foo;;
>>
yourself, if this is what you wish.
9.6 Options
*=*=*=*=*=*=*
The following command-line options are recognized by ocamlmktop.
-cclib libname Pass the -llibname option to the C linker when linking in
``custom runtime'' mode. See the corresponding option for ocamlc, in chapter
8.
-ccopt option Pass the given option to the C compiler and linker, when
linking in ``custom runtime'' mode. See the corresponding option for ocamlc,
in chapter 8.
-custom Link in ``custom runtime'' mode. See the corresponding option for
ocamlc, in chapter 8.
-I directory Add the given directory to the list of directories searched for
compiled object code files (.cmo and .cma).
-o exec-file Specify the name of the toplevel file produced by the linker.
The default is a.out.
Chapter 10 The runtime system (ocamlrun)
********************************************
The ocamlrun command executes bytecode files produced by the linking phase of
the ocamlc command.
10.1 Overview
*=*=*=*=*=*=*=*
The ocamlrun command comprises three main parts: the bytecode interpreter,
that actually executes bytecode files; the memory allocator and garbage
collector; and a set of C functions that implement primitive operations such as
input/output.
The usage for ocamlrun is:
<<
ocamlrun options bytecode-executable arg_1 ... arg_n
>>
The first non-option argument is taken to be the name of the file containing
the executable bytecode. (That file is searched in the executable path as well
as in the current directory.) The remaining arguments are passed to the Caml
Light program, in the string array Sys.argv. Element 0 of this array is the
name of the bytecode executable file; elements 1 to n are the remaining
arguments arg_1 to arg_n.
As mentioned in chapter 8, the bytecode executable files produced by the
ocamlc command are self-executable, and manage to launch the ocamlrun command
on themselves automatically. That is, assuming caml.out is a bytecode
executable file,
<<
caml.out arg_1 ... arg_n
>>
works exactly as
<<
ocamlrun caml.out arg_1 ... arg_n
>>
Notice that it is not possible to pass options to ocamlrun when invoking
caml.out directly.
Windows:
Under several versions of Windows, bytecode executable files
are self-executable only if their name ends in .exe. It is
recommended to always give .exe names to bytecode executables,
e.g. compile with ocamlc -o myprog.exe ... rather than ocamlc -o
myprog ....
10.2 Options
*=*=*=*=*=*=*=
The following command-line options are recognized by ocamlrun.
-b When the program aborts due to an uncaught exception, print a detailed
``back trace'' of the execution, showing where the exception was raised and
which function calls were outstanding at this point. The back trace is
printed only if the bytecode executable contains debugging information, i.e.
was compiled and linked with the -g option to ocamlc set. This is equivalent
to setting b=1 in the OCAMLRUNPARAM environment variable (see below).
-v Direct the memory manager to print some progress messages on standard
error. This is equivalent to setting v=63 in the OCAMLRUNPARAM environment
variable (see below).
The following environment variables are also consulted:
OCAMLRUNPARAM Set the runtime system options and garbage collection
parameters. (If OCAMLRUNPARAM is not set, CAMLRUNPARAM will be used
instead.) This variable must be a sequence of parameter specifications. A
parameter specification is an option letter followed by an = sign, a
decimal number, and an optional multiplier. There are eight options, six of
which correspond to the fields of the control record documented in section
19.9.
b (backtrace) Control the printing of a stack backtrace when an uncaught
exception aborts the program. A non-zero argument turn the backtrace
facility on; a zero argument turn it off.
s (minor_heap_size) Size of the minor heap.
i (major_heap_increment) Minimum size increment for the major heap.
o (space_overhead) The major GC speed setting.
O (max_overhead) The heap compaction trigger setting.
v (verbose) What GC messages to print to stderr. This is a sum of values
selected from the following:
1 Start of major GC cycle.
2 Minor collection and major GC slice.
4 Growing and shrinking of the heap.
8 Resizing of stacks and memory manager tables.
16 Heap compaction.
32 Change of GC parameters.
64 Computation of major GC slice size.
128 Calling of finalization functions
256 Startup messages (loading the bytecode executable file).
l (stack_limit) The limit (in words) of the stack size.
h The initial size of the major heap (in words).
The multiplier is k, M, or G, for multiplication by 2^10, 2^20, and 2^30
respectively. For example, on a 32-bit machine, under bash the command
<<
export OCAMLRUNPARAM='b=1,s=256k,v=1'
>>
tells a subsequent ocamlrun to print backtraces for uncaught exceptions,
set its initial minor heap size to 1 megabyte and print a message at the
start of each major GC cycle.
PATH List of directories searched to find the bytecode executable file.
10.3 Common errors
*=*=*=*=*=*=*=*=*=*=
This section describes and explains the most frequently encountered error
messages.
filename: no such file or directory If filename is the name of a
self-executable bytecode file, this means that either that file does not
exist, or that it failed to run the ocamlrun bytecode interpreter on itself.
The second possibility indicates that Objective Caml has not been properly
installed on your system.
Cannot exec camlrun (When launching a self-executable bytecode file.) The
ocamlrun could not be found in the executable path. Check that Objective
Caml has been properly installed on your system.
Cannot find the bytecode file The file that ocamlrun is trying to execute
(e.g. the file given as first non-option argument to ocamlrun) either does
not exist, or is not a valid executable bytecode file.
Truncated bytecode file The file that ocamlrun is trying to execute is not a
valid executable bytecode file. Probably it has been truncated or mangled
since created. Erase and rebuild it.
Uncaught exception The program being executed contains a ``stray'' exception.
That is, it raises an exception at some point, and this exception is never
caught. This causes immediate termination of the program. The name of the
exception is printed, along with its string and integer arguments (arguments
of more complex types are not correctly printed). To locate the context of
the uncaught exception, compile the program with the -g option and either
run it again under the ocamldebug debugger (see chapter 15), or run it with
ocamlrun -b or with the OCAMLRUNPARAM environment variable set to b=1.
Out of memory The program being executed requires more memory than available.
Either the program builds excessively large data structures; or the program
contains too many nested function calls, and the stack overflows. In some
cases, your program is perfectly correct, it just requires more memory than
your machine provides. In other cases, the ``out of memory'' message reveals
an error in your program: non-terminating recursive function, allocation of
an excessively large array or string, attempts to build an infinite list or
other data structure, ...
To help you diagnose this error, run your program with the -v option to
ocamlrun, or with the OCAMLRUNPARAM environment variable set to v=63. If it
displays lots of ``Growing stack...'' messages, this is probably a looping
recursive function. If it displays lots of ``Growing heap...'' messages,
with the heap size growing slowly, this is probably an attempt to construct
a data structure with too many (infinitely many?) cells. If it displays few
``Growing heap...'' messages, but with a huge increment in the heap size,
this is probably an attempt to build an excessively large array or string.
Chapter 11 Native-code compilation (ocamlopt)
*************************************************
This chapter describes the Objective Caml high-performance native-code
compiler ocamlopt, which compiles Caml source files to native code object files
and link these object files to produce standalone executables.
The native-code compiler is only available on certain platforms. It produces
code that runs faster than the bytecode produced by ocamlc, at the cost of
increased compilation time and executable code size. Compatibility with the
bytecode compiler is extremely high: the same source code should run
identically when compiled with ocamlc and ocamlopt.
It is not possible to mix native-code object files produced by ocamlc with
bytecode object files produced by ocamlopt: a program must be compiled entirely
with ocamlopt or entirely with ocamlc. Native-code object files produced by
ocamlopt cannot be loaded in the toplevel system ocaml.
11.1 Overview of the compiler
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The ocamlopt command has a command-line interface very close to that of
ocamlc. It accepts the same types of arguments:
- Arguments ending in .mli are taken to be source files for compilation unit
interfaces. Interfaces specify the names exported by compilation units: they
declare value names with their types, define public data types, declare
abstract data types, and so on. From the file x.mli, the ocamlopt compiler
produces a compiled interface in the file x.cmi. The interface produced is
identical to that produced by the bytecode compiler ocamlc.
- Arguments ending in .ml are taken to be source files for compilation unit
implementations. Implementations provide definitions for the names exported
by the unit, and also contain expressions to be evaluated for their
side-effects. From the file x.ml, the ocamlopt compiler produces two files:
x.o, containing native object code, and x.cmx, containing extra information
for linking and optimization of the clients of the unit. The compiled
implementation should always be referred to under the name x.cmx (when given
a .o file, ocamlopt assumes that it contains code compiled from C, not from
Caml).
The implementation is checked against the interface file x.mli (if it exists)
as described in the manual for ocamlc (chapter 8).
- Arguments ending in .cmx are taken to be compiled object code. These files
are linked together, along with the object files obtained by compiling .ml
arguments (if any), and the Caml Light standard library, to produce a
native-code executable program. The order in which .cmx and .ml arguments
are presented on the command line is relevant: compilation units are
initialized in that order at run-time, and it is a link-time error to use a
component of a unit before having initialized it. Hence, a given x.cmx file
must come before all .cmx files that refer to the unit x.
- Arguments ending in .cmxa are taken to be libraries of object code. Such a
library packs in two files (lib.cmxa and lib.a) a set of object files
(.cmx/.o files). Libraries are build with ocamlopt -a (see the description
of the -a option below). The object files contained in the library are
linked as regular .cmx files (see above), in the order specified when the
library was built. The only difference is that if an object file contained
in a library is not referenced anywhere in the program, then it is not
linked in.
- Arguments ending in .c are passed to the C compiler, which generates a .o
object file. This object file is linked with the program.
- Arguments ending in .o or .a are assumed to be C object files and libraries.
They are linked with the program.
The output of the linking phase is a regular Unix executable file. It does
not need ocamlrun to run.
11.2 Options
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The following command-line options are recognized by ocamlopt.
-a Build a library (.cmxa/.a file) with the object files (.cmx/.o files)
given on the command line, instead of linking them into an executable file.
The name of the library can be set with the -o option. The default name is
library.cmxa.
If -cclib or -ccopt options are passed on the command line, these options are
stored in the resulting .cmxa library. Then, linking with this library
automatically adds back the -cclib and -ccopt options as if they had been
provided on the command line, unless the -noautolink option is given.
-c Compile only. Suppress the linking phase of the compilation. Source code
files are turned into compiled files, but no executable file is produced.
This option is useful to compile modules separately.
-cc ccomp Use ccomp as the C linker called to build the final executable and
as the C compiler for compiling .c source files.
-cclib -llibname Pass the -llibname option to the linker. This causes the
given C library to be linked with the program.
-ccopt option Pass the given option to the C compiler and linker. For
instance, -ccopt -Ldir causes the C linker to search for C libraries in
directory dir.
-compact Optimize the produced code for space rather than for time. This
results in slightly smaller but slightly slower programs. The default is to
optimize for speed.
-i Cause the compiler to print all defined names (with their inferred types
or their definitions) when compiling an implementation (.ml file). This can
be useful to check the types inferred by the compiler. Also, since the
output follows the syntax of interfaces, it can help in writing an explicit
interface (.mli file) for a file: just redirect the standard output of the
compiler to a .mli file, and edit that file to remove all declarations of
unexported names.
-I directory Add the given directory to the list of directories searched for
compiled interface files (.cmi), compiled object code files (.cmx), and
libraries (.cmxa). By default, the current directory is searched first, then
the standard library directory. Directories added with -I are searched after
the current directory, in the order in which they were given on the command
line, but before the standard library directory.
If the given directory starts with +, it is taken relative to the standard
library directory. For instance, -I +labltk adds the subdirectory labltk of
the standard library to the search path.
-inline n Set aggressiveness of inlining to n, where n is a positive integer.
Specifying -inline 0 prevents all functions from being inlined, except those
whose body is smaller than the call site. Thus, inlining causes no expansion
in code size. The default aggressiveness, -inline 1, allows slightly larger
functions to be inlined, resulting in a slight expansion in code size.
Higher values for the -inline option cause larger and larger functions to
become candidate for inlining, but can result in a serious increase in code
size.
-labels Switch to the commuting label mode of compilation, meaning that
labeling rules are applied strictly, and commutation between labeled
arguments is allowed. (See section 2.1.4.) This mode cannot be used to
compile a program written in the default classic style, but modules written
in the two styles can be mixed in the same application.
-linkall Forces all modules contained in libraries to be linked in. If this
flag is not given, unreferenced modules are not linked in. When building a
library (-a flag), setting the -linkall flag forces all subsequent links of
programs involving that library to link all the modules contained in the
library.
-noassert Turn assertion checking off: assertions are not compiled. This flag
has no effect when linking already compiled files.
-noautolink When linking .cmxa libraries, ignore -cclib and -ccopt options
potentially contained in the libraries (if these options were given when
building the libraries). This can be useful if a library contains incorrect
specifications of C libraries or C options; in this case, during linking,
set -noautolink and pass the correct C libraries and options on the command
line.
-o exec-file Specify the name of the output file produced by the linker. The
default output name is a.out, in keeping with the Unix tradition. If the -a
option is given, specify the name of the library produced. If the
-output-obj option is given, specify the name of the output file produced.
-output-obj Cause the linker to produce a C object file instead of an
executable file. This is useful to wrap Caml code as a C library, callable
from any C program. See chapter 17, section 17.7.5. The name of the output
object file is camlprog.o by default; it can be set with the -o option.
-p Generate extra code to write profile information when the program is
executed. The profile information can then be examined with the analysis
program gprof. (See chapter 16 for more information on profiling.) The -p
option must be given both at compile-time and at link-time. Linking object
files not compiled with -p is possible, but results in less precise
profiling.
Unix:
See the Unix manual page for gprof(1) for more information
about the profiles.
Full support for gprof is only available for certain
platforms (currently: Intel x86/Linux and Alpha/Digital
Unix). On other platforms, the -p option will result in a
less precise profile (no call graph information, only a time
profile).
Windows:
The -p option does not work under Windows.
-pp command Cause the compiler to call the given command as a preprocessor
for each source file. The output of command is redirected to an intermediate
file, which is compiled. If there are no compilation errors, the
intermediate file is deleted afterwards. The name of this file is built from
the basename of the source file with the extension .ppi for an interface
(.mli) file and .ppo for an implementation (.ml) file.
-rectypes Allow arbitrary recursive types during type-checking. By default,
only recursive types where the recursion goes through an object type are
supported.
-S Keep the assembly code produced during the compilation. The assembly code
for the source file x.ml is saved in the file x.s.
-thread Compile or link multithreaded programs, in combination with the
threads library described in chapter 23. What this option actually does is
select a special, thread-safe version of the standard library.
-unsafe Turn bound checking off on array and string accesses (the v.(i) and
s.[i] constructs). Programs compiled with -unsafe are therefore faster, but
unsafe: anything can happen if the program accesses an array or string
outside of its bounds.
-v Print the version number of the compiler.
-w warning-list Enable or disable warnings according to the argument
warning-list. The argument is a string of one or several characters, with
the following meaning for each character:
A/a enable/disable all warnings
F/f enable/disable warnings for partially applied functions (i.e. f x;
expr where the application f x has a function type).
M/m enable/disable warnings for overriden methods.
P/p enable/disable warnings for partial matches (missing cases in pattern
matchings).
S/s enable/disable warnings for statements that do not have type unit
(e.g. expr1; expr2 when expr1 does not have type unit).
U/u enable/disable warnings for unused (redundant) match cases.
V/v enable/disable warnings for hidden instance variables.
X/x enable/disable all other warnings.
The default setting is -w A (all warnings enabled).
-warn-error warning-list Turn the warnings indicated in the argument
warning-list into errors. The compiler will stop on an error as soon as one
of these warnings is emitted, instead of going on. The warning-list is a
string of one or several characters, with the same meaning as for the -w
option: an uppercase character turns the corresponding warning into an
error, a lowercase character leaves it as a warning. The default setting is
-warn-error a (all warnings are not treated as errors).
-where Print the location of the standard library.
11.3 Common errors
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The error messages are almost identical to those of ocamlc. See section 8.4.
11.4 Compatibility with the bytecode compiler
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This section lists the known incompatibilities between the bytecode compiler
and the native-code compiler. Except on those points, the two compilers should
generate code that behave identically.
- The following operations abort the program (either by printing an error
message or just via an hardware trap or fatal Unix signal) instead of
raising an exception:
- integer division by zero, modulus by zero;
- stack overflow;
- on the Alpha processor only, floating-point operations involving infinite
or denormalized numbers (all other processors supported by ocamlopt treat
these numbers correctly, as per the IEEE 754 standard).
In particular, notice that stack overflow caused by excessively deep
recursion is reported by most Unix kernels as a ``segmentation violation''
signal.
- Signals are detected only when the program performs an allocation in the
heap. That is, if a signal is delivered while in a piece of code that does
not allocate, its handler will not be called until the next heap allocation.
The best way to avoid running into those incompatibilities is to never trap
the Division_by_zero and Stack_overflow exceptions, thus also treating them as
fatal errors with the bytecode compiler as well as with the native-code
compiler. Test the divisor before performing the operation instead of trapping
the exception afterwards.
Chapter 12 Lexer and parser generators (ocamllex, ocamlyacc)
****************************************************************
This chapter describes two program generators: ocamllex, that produces a
lexical analyzer from a set of regular expressions with associated semantic
actions, and ocamlyacc, that produces a parser from a grammar with associated
semantic actions.
These program generators are very close to the well-known lex and yacc
commands that can be found in most C programming environments. This chapter
assumes a working knowledge of lex and yacc: while it describes the input
syntax for ocamllex and ocamlyacc and the main differences with lex and yacc,
it does not explain the basics of writing a lexer or parser description in lex
and yacc. Readers unfamiliar with lex and yacc are referred to ``Compilers:
principles, techniques, and tools'' by Aho, Sethi and Ullman (Addison-Wesley,
1986), or ``Lex & Yacc'', by Levine, Mason and Brown (O'Reilly, 1992).
12.1 Overview of ocamllex
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The ocamllex command produces a lexical analyzer from a set of regular
expressions with attached semantic actions, in the style of lex. Assuming the
input file is lexer.mll, executing
<<
ocamllex lexer.mll
>>
produces Caml code for a lexical analyzer in file lexer.ml. This file
defines one lexing function per entry point in the lexer definition. These
functions have the same names as the entry points. Lexing functions take as
argument a lexer buffer, and return the semantic attribute of the corresponding
entry point.
Lexer buffers are an abstract data type implemented in the standard library
module Lexing. The functions Lexing.from_channel, Lexing.from_string and
Lexing.from_function create lexer buffers that read from an input channel, a
character string, or any reading function, respectively. (See the description
of module Lexing in chapter 18.)
When used in conjunction with a parser generated by ocamlyacc, the semantic
actions compute a value belonging to the type token defined by the generated
parsing module. (See the description of ocamlyacc below.)
12.2 Syntax of lexer definitions
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The format of lexer definitions is as follows:
<<
{ header }
let ident = regexp ...
rule entrypoint =
parse regexp { action }
| ...
| regexp { action }
and entrypoint =
parse ...
and ...
{ trailer }
>>
Comments are delimited by (* and *), as in Caml.
12.2.1 Header and trailer
===========================
The header and trailer sections are arbitrary Caml text enclosed in curly
braces. Either or both can be omitted. If present, the header text is copied as
is at the beginning of the output file and the trailer text at the end.
Typically, the header section contains the `open' directives required by the
actions, and possibly some auxiliary functions used in the actions.
12.2.2 Naming regular expressions
===================================
Between the header and the entry points, one can give names to
frequently-occurring regular expressions. This is written let ident = regexp.
In following regular expressions, the identifier ident can be used as shorthand
for regexp.
12.2.3 Entry points
=====================
The names of the entry points must be valid identifiers for Caml values
(starting with a lowercase letter).
12.2.4 Regular expressions
============================
The regular expressions are in the style of lex, with a more Caml-like
syntax.
' char ' A character constant, with the same syntax as Objective Caml
character constants. Match the denoted character.
_ (Underscore.) Match any character.
eof Match the end of the lexer input.
Note: On some systems, with interactive input, and end-of-file may be followed
by more characters. However, ocamllex will not correctly handle regular
expressions that contain eof followed by something else.
" string " A string constant, with the same syntax as Objective Caml string
constants. Match the corresponding sequence of characters.
[ character-set ] Match any single character belonging to the given character
set. Valid character sets are: single character constants ' c '; ranges of
characters ' c_1 ' - ' c_2 ' (all characters between c_1 and c_2,
inclusive); and the union of two or more character sets, denoted by
concatenation.
[ ^ character-set ] Match any single character not belonging to the given
character set.
regexp * (Repetition.) Match the concatenation of zero or more strings that
match regexp.
regexp + (Strict repetition.) Match the concatenation of one or more strings
that match regexp.
regexp ? (Option.) Match either the empty string, or a string matching
regexp.
regexp_1 | regexp_2 (Alternative.) Match any string that matches either
regexp_1 or regexp_2
regexp_1 regexp_2 (Concatenation.) Match the concatenation of two strings,
the first matching regexp_1, the second matching regexp_2.
( regexp ) Match the same strings as regexp.
ident Reference the regular expression bound to ident by an earlier let ident
= regexp definition.
Concerning the precedences of operators, * and + have highest precedence,
followed by ?, then concatenation, then | (alternation).
12.2.5 Actions
================
The actions are arbitrary Caml expressions. They are evaluated in a context
where the identifier lexbuf is bound to the current lexer buffer. Some typical
uses for lexbuf, in conjunction with the operations on lexer buffers provided
by the Lexing standard library module, are listed below.
Lexing.lexeme lexbuf Return the matched string.
Lexing.lexeme_char lexbuf n Return the n^th character in the matched string.
The first character corresponds to n = 0.
Lexing.lexeme_start lexbuf Return the absolute position in the input text of
the beginning of the matched string. The first character read from the input
text has position 0.
Lexing.lexeme_end lexbuf Return the absolute position in the input text of
the end of the matched string. The first character read from the input text
has position 0.
entrypoint lexbuf (Where entrypoint is the name of another entry point in the
same lexer definition.) Recursively call the lexer on the given entry point.
Useful for lexing nested comments, for example.
12.2.6 Reserved identifiers
=============================
All identifiers starting with __ocaml_lex are reserved for use by ocamllex;
do not use any such identifier in your programs.
12.3 Overview of ocamlyacc
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The ocamlyacc command produces a parser from a context-free grammar
specification with attached semantic actions, in the style of yacc. Assuming
the input file is grammar.mly, executing
<<
ocamlyacc options grammar.mly
>>
produces Caml code for a parser in the file grammar.ml, and its interface in
file grammar.mli.
The generated module defines one parsing function per entry point in the
grammar. These functions have the same names as the entry points. Parsing
functions take as arguments a lexical analyzer (a function from lexer buffers
to tokens) and a lexer buffer, and return the semantic attribute of the
corresponding entry point. Lexical analyzer functions are usually generated
from a lexer specification by the ocamllex program. Lexer buffers are an
abstract data type implemented in the standard library module Lexing. Tokens
are values from the concrete type token, defined in the interface file
grammar.mli produced by ocamlyacc.
12.4 Syntax of grammar definitions
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Grammar definitions have the following format:
<<
%{
header
%}
declarations
%%
rules
%%
trailer
>>
Comments are enclosed between `/*' and `*/' (as in C) in the ``declarations''
and ``rules'' sections, and between `(*' and `*)' (as in Caml) in the
``header'' and ``trailer'' sections.
12.4.1 Header and trailer
===========================
The header and the trailer sections are Caml code that is copied as is into
file grammar.ml. Both sections are optional. The header goes at the beginning
of the output file; it usually contains open directives and auxiliary functions
required by the semantic actions of the rules. The trailer goes at the end of
the output file.
12.4.2 Declarations
=====================
Declarations are given one per line. They all start with a `%' sign.
%token symbol ... symbol Declare the given symbols as tokens (terminal
symbols). These symbols are added as constant constructors for the token
concrete type.
%token < type > symbol ... symbol Declare the given symbols as tokens with an
attached attribute of the given type. These symbols are added as
constructors with arguments of the given type for the token concrete type.
The type part is an arbitrary Caml type expression, except that all type
constructor names must be fully qualified (e.g. Modname.typename) for all
types except standard built-in types, even if the proper `open' directives
(e.g. `open Modname') were given in the header section. That's because the
header is copied only to the .ml output file, but not to the .mli output
file, while the type part of a `%token' declaration is copied to both.
%start symbol ... symbol Declare the given symbols as entry points for the
grammar. For each entry point, a parsing function with the same name is
defined in the output module. Non-terminals that are not declared as entry
points have no such parsing function. Start symbols must be given a type
with the `%type' directive below.
%type < type > symbol ... symbol Specify the type of the semantic attributes
for the given symbols. This is mandatory for start symbols only. Other
nonterminal symbols need not be given types by hand: these types will be
inferred when running the output files through the Objective Caml compiler
(unless the `-s' option is in effect). The type part is an arbitrary Caml
type expression, except that all type constructor names must be fully
qualified, as explained above for %token.
%left symbol ... symbol
%right symbol ... symbol
%nonassoc symbol ... symbol
Associate precedences and associativities to the given symbols. All symbols on
the same line are given the same precedence. They have higher precedence
than symbols declared before in a `%left', `%right' or `%nonassoc' line.
They have lower precedence than symbols declared after in a `%left',
`%right' or `%nonassoc' line. The symbols are declared to associate to the
left (`%left'), to the right (`%right'), or to be non-associative
(`%nonassoc'). The symbols are usually tokens. They can also be dummy
nonterminals, for use with the `%prec' directive inside the rules.
12.4.3 Rules
==============
The syntax for rules is as usual:
<<
nonterminal :
symbol ... symbol { semantic-action }
| ...
| symbol ... symbol { semantic-action }
;
>>
Rules can also contain the `%prec 'symbol directive in the right-hand side
part, to override the default precedence and associativity of the rule with the
precedence and associativity of the given symbol.
Semantic actions are arbitrary Caml expressions, that are evaluated to
produce the semantic attribute attached to the defined nonterminal. The
semantic actions can access the semantic attributes of the symbols in the
right-hand side of the rule with the `$' notation: `$1' is the attribute for
the first (leftmost) symbol, `$2' is the attribute for the second symbol, etc.
The rules may contain the special symbol error to indicate resynchronization
points, as in yacc.
Actions occurring in the middle of rules are not supported.
12.4.4 Error handling
=======================
Error recovery is supported as follows: when the parser reaches an error
state (no grammar rules can apply), it calls a function named parse_error with
the string "syntax error" as argument. The default parse_error function does
nothing and returns, thus initiating error recovery (see below). The user can
define a customized parse_error function in the header section of the grammar
file.
The parser also enters error recovery mode if one of the grammar actions
raises the Parsing.Parse_error exception.
In error recovery mode, the parser discards states from the stack until it
reaches a place where the error token can be shifted. It then discards tokens
from the input until it finds three successive tokens that can be accepted, and
starts processing with the first of these. If no state can be uncovered where
the error token can be shifted, then the parser aborts by raising the
Parsing.Parse_error exception.
Refer to documentation on yacc for more details and guidance in how to use
error recovery.
12.5 Options
*=*=*=*=*=*=*=
The ocamlyacc command recognizes the following options:
-v Generate a description of the parsing tables and a report on conflicts
resulting from ambiguities in the grammar. The description is put in file
grammar.output.
-bprefix Name the output files prefix.ml, prefix.mli, prefix.output, instead
of the default naming convention.
12.6 A complete example
*=*=*=*=*=*=*=*=*=*=*=*=*
The all-time favorite: a desk calculator. This program reads arithmetic
expressions on standard input, one per line, and prints their values. Here is
the grammar definition:
<<
/* File parser.mly */
%token <int> INT
%token PLUS MINUS TIMES DIV
%token LPAREN RPAREN
%token EOL
%left PLUS MINUS /* lowest precedence */
%left TIMES DIV /* medium precedence */
%nonassoc UMINUS /* highest precedence */
%start main /* the entry point */
%type <int> main
%%
main:
expr EOL { $1 }
;
expr:
INT { $1 }
| LPAREN expr RPAREN { $2 }
| expr PLUS expr { $1 + $3 }
| expr MINUS expr { $1 - $3 }
| expr TIMES expr { $1 * $3 }
| expr DIV expr { $1 / $3 }
| MINUS expr %prec UMINUS { - $2 }
;
>>
Here is the definition for the corresponding lexer:
<<
(* File lexer.mll *)
{
open Parser (* The type token is defined in parser.mli *)
exception Eof
}
rule token = parse
[' ' '\t'] { token lexbuf } (* skip blanks *)
| ['\n' ] { EOL }
| ['0'-'9']+ { INT(int_of_string(Lexing.lexeme lexbuf)) }
| '+' { PLUS }
| '-' { MINUS }
| '*' { TIMES }
| '/' { DIV }
| '(' { LPAREN }
| ')' { RPAREN }
| eof { raise Eof }
>>
Here is the main program, that combines the parser with the lexer:
<<
(* File calc.ml *)
let _ =
try
let lexbuf = Lexing.from_channel stdin in
while true do
let result = Parser.main Lexer.token lexbuf in
print_int result; print_newline(); flush stdout
done
with Lexer.Eof ->
exit 0
>>
To compile everything, execute:
<<
ocamllex lexer.mll # generates lexer.ml
ocamlyacc parser.mly # generates parser.ml and parser.mli
ocamlc -c parser.mli
ocamlc -c lexer.ml
ocamlc -c parser.ml
ocamlc -c calc.ml
ocamlc -o calc lexer.cmo parser.cmo calc.cmo
>>
12.7 Common errors
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ocamllex: transition table overflow, automaton is too big
The deterministic automata generated by ocamllex are limited to at most 32767
transitions. The message above indicates that your lexer definition is too
complex and overflows this limit. This is commonly caused by lexer
definitions that have separate rules for each of the alphabetic keywords of
the language, as in the following example.
<<
rule token = parse
"keyword1" { KWD1 }
| "keyword2" { KWD2 }
| ...
| "keyword100" { KWD100 }
| ['A'-'Z' 'a'-'z'] ['A'-'Z' 'a'-'z' '0'-'9' '_'] *
{ IDENT(Lexing.lexeme lexbuf) }
>>
To keep the generated automata small, rewrite those definitions with only one
general ``identifier'' rule, followed by a hashtable lookup to separate
keywords from identifiers:
<<
{ let keyword_table = Hashtbl.create 53
let _ =
List.iter (fun (kwd, tok) -> Hashtbl.add keyword_table kwd tok)
[ "keyword1", KWD1;
"keyword2", KWD2; ...
"keyword100", KWD100 ]
}
rule token = parse
['A'-'Z' 'a'-'z'] ['A'-'Z' 'a'-'z' '0'-'9' '_'] *
{ let id = Lexing.lexeme lexbuf in
try
Hashtbl.find keyword_table s
with Not_found ->
IDENT s }
>>
Chapter 13 Dependency generator (ocamldep)
**********************************************
The ocamldep command scans a set of Objective Caml source files (.ml and .mli
files) for references to external compilation units, and outputs dependency
lines in a format suitable for the make utility. This ensures that make will
compile the source files in the correct order, and recompile those files that
need to when a source file is modified.
The typical usage is:
<<
ocamldep options *.mli *.ml > .depend
>>
where *.mli *.ml expands to all source files in the current directory and
.depend is the file that should contain the dependencies. (See below for a
typical Makefile.)
Dependencies are generated both for compiling with the bytecode compiler
ocamlc and with the native-code compiler ocamlopt.
13.1 Options
*=*=*=*=*=*=*=
The following command-line option is recognized by ocamldep.
-I directory Add the given directory to the list of directories searched for
source files. If a source file foo.ml mentions an external compilation unit
Bar, a dependency on that unit's interface bar.cmi is generated only if the
source for bar is found in the current directory or in one of the
directories specified with -I. Otherwise, Bar is assumed to be a module form
the standard library, and no dependencies are generated. For programs that
span multiple directories, it is recommended to pass ocamldep the same -I
options that are passed to the compiler.
-native Generate dependencies for a pure native-code program (no bytecode
version). When an implementation file (.ml file) has no explicit interface
file (.mli file), ocamldep generates dependencies on the bytecode compiled
file (.cmo file) to reflect interface changes. This can cause unnecessary
bytecode recompilations for programs that are compiled to native-code only.
The flag -native causes dependencies on native compiled files (.cmx) to be
generated instead of on .cmo files. (This flag makes no difference if all
source files have explicit .mli interface files.)
13.2 A typical Makefile
*=*=*=*=*=*=*=*=*=*=*=*=*
Here is a template Makefile for a Objective Caml program.
<<
OCAMLC=ocamlc
OCAMLOPT=ocamlopt
OCAMLDEP=ocamldep
INCLUDES= # all relevant -I options here
OCAMLFLAGS=$(INCLUDES) # add other options for ocamlc here
OCAMLOPTFLAGS=$(INCLUDES) # add other options for ocamlopt here
# prog1 should be compiled to bytecode, and is composed of three
# units: mod1, mod2 and mod3.
# The list of object files for prog1
PROG1_OBJS=mod1.cmo mod2.cmo mod3.cmo
prog1: $(PROG1_OBJS)
$(OCAMLC) -o prog1 $(OCAMLFLAGS) $(PROG1_OBJS)
# prog2 should be compiled to native-code, and is composed of two
# units: mod4 and mod5.
# The list of object files for prog2
PROG2_OBJS=mod4.cmx mod5.cmx
prog2: $(PROG2_OBJS)
$(OCAMLOPT) -o prog2 $(OCAMLFLAGS) $(PROG2_OBJS)
# Common rules
.SUFFIXES: .ml .mli .cmo .cmi .cmx
.ml.cmo:
$(OCAMLC) $(OCAMLFLAGS) -c $<
.mli.cmi:
$(OCAMLC) $(OCAMLFLAGS) -c $<
.ml.cmx:
$(OCAMLOPT) $(OCAMLOPTFLAGS) -c $<
# Clean up
clean:
rm -f prog1 prog2
rm -f *.cm[iox]
# Dependencies
depend:
$(OCAMLDEP) $(INCLUDES) *.mli *.ml > .depend
include .depend
>>
Chapter 14 The browser/editor (ocamlbrowser)
************************************************
This chapter describes OCamlBrowser, a source and compiled interface browser,
written using LablTk. This is a useful companion to the programmer.
Its functions are:
- navigation through Objective Caml's modules (using compiled interfaces).
- source editing, type-checking, and browsing.
- integrated Objective Caml shell, running as a subprocess.
14.1 Invocation
*=*=*=*=*=*=*=*=*
The browser is started by the command ocamlrowser, as follows:
<<
ocamlbrowser options
>>
The following command-line options are recognized by ocamlbrowser.
-I directory Add the given directory to the list of directories searched for
source and compiled files. By default, only the standard library directory
is searched. The standard library can also be changed by setting the CAMLLIB
environment variable.
-labels Switch to the commuting label mode of compilation, meaning that
labeling rules are applied strictly, and commutation between arguments is
allowed. (See section 2.1.4.)
-rectypes Allow arbitrary recursive types during type-checking. By default,
only recursive types where the recursion goes through an object type are
supported.
-w warning-list Enable or disable warnings according to the argument
warning-list.
All options can also be modified inside the application by the Modules - Path
editor and Compiler - Preferences commands. They are inherited when you start a
toplevel shell.
14.2 Viewer
*=*=*=*=*=*=*
This is the first window you get when you start OCamlBrowser. It displays
the list of modules in the load path. Click on one to start your trip.
- The entry line at the bottom allows one to search for an identifier in all
modules (wildcards ``?'' and ``*'' allowed). If the input contains an arrow
(``->''), the search is done by type inclusion (cf. Search Symbol -
Included type).
- The Close all button is there to dismiss the windows created during you
trip (every click creates one...) By double-clicking on it you will quit
the browser.
- File - Open and File - Editor give access to the editor.
- File - Shell creates an Objective Caml subprocess in a shell.
- Modules - Path editor changes the load path. Modules - Reset cache rescans
the load path and resets the module cache. Do it if you recompile some
interface, or get confused about what is in the cache.
- Modules - Search symbol allows to search a symbol either by its name, like
the bottom line of the viewer, or, more interestingly, by its type. Exact
type searches for a type with exactly the same information as the pattern
(variables match only variables). Included type allows to give only partial
information: the actual type may take more arguments and return more
results, and variables in the pattern match anything. In both cases,
argument and tuple order is irrelevant (1), and unlabeled arguments in the
pattern match any label.
14.3 Module walking
*=*=*=*=*=*=*=*=*=*=*
Each module is displayed in its own window.
At the top, a scrollable list of the defined identifiers. If you click on
one, this will either create a new window (if this is a sub-module) or display
the signature for this identifier below.
Signatures are clickable. Double clicking with the left mouse button on an
identifier in a signature brings you to its signature, inside its module box.
A single click on the right button pops up a menu displaying the type
declaration for the selected identifier. Its title, when selectable, also
brings you to its signature.
At the bottom, a series of buttons, depending on the context.
- Show all displays the signature of the whole module.
- Detach copies the currently displayed signature in a new window, to keep
it.
- Impl and Intf bring you to the implementation or interface of the currently
displayed signature, if it is available.
Control-S lets you search a string in the signature.
14.4 File editor
*=*=*=*=*=*=*=*=*=
You can edit files with it, if you're not yet used to emacs. Otherwise you
can use it as a browser, making occasional corrections.
The Edit menu contains commands for jump (C-g), search (C-s), and sending the
current phrase (or selection if some text is selected) to a sub-shell (M-x).
For this last option, you may choose the shell via a dialog.
Essential functions are in the Compiler menu.
- Preferences opens a dialog to set internals of the editor and type-checker.
- Lex adds colors according to lexical categories.
- Typecheck verifies typing, and memorizes to let one see an expression's
type by double-clicking on it. This is also valid for interfaces. If an
error occurs, the part of the interface preceding the error is computed.
After typechecking, pressing the right button pops up a menu giving the type
of the pointed expression, and eventually allowing to follow some links.
- Clear errors dismisses type-checker error messages and warnings.
- Signature shows the signature of the current file (after type checking).
14.5 Shell
*=*=*=*=*=*=
When you create a shell, a dialog is presented to you, letting you choose
which command you want to run, and the title of the shell (to choose it in the
Editor).
The executed subshell is given the current load path.
- File use a source file or load a bytecode file. You may also import the
browser's path into the subprocess.
- History M-p and M-n browse up and down.
- Signal C-c interrupts, and you can also kill the subprocess.
---------------------------------------
(1) To avoid combinatorial explosion of the search space, optional arguments
in the actual type are ignored in the actual if (1) there are too many of
them, and (2) they do not appear explicitly in the pattern.
Chapter 15 The debugger (ocamldebug)
****************************************
This chapter describes the Objective Caml source-level replay debugger
ocamldebug.
Unix:
The debugger is available on Unix systems that provides BSD
sockets.
Windows:
The debugger is available under the Cygwin port of Objective
Caml, but not under the native Win32 port.
MacOS:
The debugger is not available.
15.1 Compiling for debugging
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Before the debugger can be used, the program must be compiled and linked with
the -g option: all .cmo and .cma files that are part of the program should have
been created with ocamlc -g, and they must be linked together with ocamlc -g.
Compiling with -g entails no penalty on the running time of programs: object
files and bytecode executable files are bigger and take longer to produce, but
the executable files run at exactly the same speed as if they had been compiled
without -g.
15.2 Invocation
*=*=*=*=*=*=*=*=*
15.2.1 Starting the debugger
==============================
The Objective Caml debugger is invoked by running the program ocamldebug with
the name of the bytecode executable file as first argument:
<<
ocamldebug [options] program [arguments]
>>
The arguments following program are optional, and are passed as command-line
arguments to the program being debugged. (See also the set arguments command.)
The following command-line options are recognized:
-I directory Add directory to the list of directories searched for source
files and compiled files. (See also the directory command.)
-s socket Use socket for communicating with the debugged program. See the
description of the command set socket (section 15.8.6) for the format of
socket.
-c count Set the maximum number of simultaneously live checkpoints to count.
-cd directory Run the debugger program from the working directory directory,
instead of the current directory. (See also the cd command.)
-emacs Tell the debugger it is executed under Emacs. (See section 15.10 for
information on how to run the debugger under Emacs.)
15.2.2 Exiting the debugger
=============================
The command quit exits the debugger. You can also exit the debugger by typing
an end-of-file character (usually ctrl-D).
Typing an interrupt character (usually ctrl-C) will not exit the debugger,
but will terminate the action of any debugger command that is in progress and
return to the debugger command level.
15.3 Commands
*=*=*=*=*=*=*=*
A debugger command is a single line of input. It starts with a command name,
which is followed by arguments depending on this name. Examples:
<<
run
goto 1000
set arguments arg1 arg2
>>
A command name can be truncated as long as there is no ambiguity. For
instance, go 1000 is understood as goto 1000, since there are no other commands
whose name starts with go. For the most frequently used commands, ambiguous
abbreviations are allowed. For instance, r stands for run even though there are
others commands starting with r. You can test the validity of an abbreviation
using the help command.
If the previous command has been successful, a blank line (typing just RET)
will repeat it.
15.3.1 Getting help
=====================
The Objective Caml debugger has a simple on-line help system, which gives a
brief description of each command and variable.
help Print the list of commands.
help command Give help about the command command.
help set variable, help show variable Give help about the variable variable.
The list of all debugger variables can be obtained with help set.
help info topic Give help about topic. Use help info to get a list of known
topics.
15.3.2 Accessing the debugger state
=====================================
set variable value Set the debugger variable variable to the value value.
show variable Print the value of the debugger variable variable.
info subject Give information about the given subject. For instance, info
breakpoints will print the list of all breakpoints.
15.4 Executing a program
*=*=*=*=*=*=*=*=*=*=*=*=*=
15.4.1 Events
===============
Events are ``interesting'' locations in the source code, corresponding to the
beginning or end of evaluation of ``interesting'' sub-expressions. Events are
the unit of single-stepping (stepping goes to the next or previous event
encountered in the program execution). Also, breakpoints can only be set at
events. Thus, events play the role of line numbers in debuggers for
conventional languages.
During program execution, a counter is incremented at each event encountered.
The value of this counter is referred as the current time. Thanks to reverse
execution, it is possible to jump back and forth to any time of the execution.
Here is where the debugger events (written §§) are located in the source
code:
- Following a function application:
<<
(f arg)§§
>>
- On entrance to a function:
<<
fun x y z -> §§ ...
>>
- On each case of a pattern-matching definition (function, match...with
construct, try...with construct):
<<
function pat1 -> §§ expr1
| ...
| patN -> §§ exprN
>>
- Between subexpressions of a sequence:
<<
expr1; §§ expr2; §§ ...; §§ exprN
>>
- In the two branches of a conditional expression:
<<
if cond then §§ expr1 else §§ expr2
>>
- At the beginning of each iteration of a loop:
<<
while cond do §§ body done
for i = a to b do §§ body done
>>
Exceptions: A function application followed by a function return is replaced
by the compiler by a jump (tail-call optimization). In this case, no event is
put after the function application.
15.4.2 Starting the debugged program
======================================
The debugger starts executing the debugged program only when needed. This
allows setting breapoints or assigning debugger variables before execution
starts. There are several ways to start execution:
run Run the program until a breakpoint is hit, or the program terminates.
step 0 Load the program and stop on the first event.
goto time Load the program and execute it until the given time. Useful when
you already know approximately at what time the problem appears. Also useful
to set breakpoints on function values that have not been computed at time 0
(see section 15.5).
The execution of a program is affected by certain information it receives
when the debugger starts it, such as the command-line arguments to the program
and its working directory. The debugger provides commands to specify this
information (set arguments and cd). These commands must be used before program
execution starts. If you try to change the arguments or the working directory
after starting your program, the debugger will kill the program (after asking
for confirmation).
15.4.3 Running the program
============================
The following commands execute the program forward or backward, starting at
the current time. The execution will stop either when specified by the command
or when a breakpoint is encountered.
run Execute the program forward from current time. Stops at next breakpoint
or when the program terminates.
reverse Execute the program backward from current time. Mostly useful to go
to the last breakpoint encountered before the current time.
step [count] Run the program and stop at the next event. With an argument, do
it count times.
backstep [count] Run the program backward and stop at the previous event.
With an argument, do it count times.
next [count] Run the program and stop at the next event, skipping over
function calls. With an argument, do it count times.
previous [count] Run the program backward and stop at the previous event,
skipping over function calls. With an argument, do it count times.
finish Run the program until the current function returns.
start Run the program backward and stop at the first event before the current
function invocation.
15.4.4 Time travel
====================
You can jump directly to a given time, without stopping on breakpoints, using
the goto command.
As you move through the program, the debugger maintains an history of the
successive times you stop at. The last command can be used to revisit these
times: each last command moves one step back through the history. That is
useful mainly to undo commands such as step and next.
goto time Jump to the given time.
last [count] Go back to the latest time recorded in the execution history.
With an argument, do it count times.
set history size Set the size of the execution history.
15.4.5 Killing the program
============================
kill Kill the program being executed. This command is mainly useful if you
wish to recompile the program without leaving the debugger.
15.5 Breakpoints
*=*=*=*=*=*=*=*=*=
A breakpoint causes the program to stop whenever a certain point in the
program is reached. It can be set in several ways using the break command.
Breakpoints are assigned numbers when set, for further reference. The most
comfortable way to set breakpoints is through the Emacs interface (see section
15.10).
break Set a breakpoint at the current position in the program execution. The
current position must be on an event (i.e., neither at the beginning, nor at
the end of the program).
break function Set a breakpoint at the beginning of function. This works only
when the functional value of the identifier function has been computed and
assigned to the identifier. Hence this command cannot be used at the very
beginning of the program execution, when all identifiers are still
undefined; use goto time to advance execution until the functional value is
available.
break @ [module] line Set a breakpoint in module module (or in the current
module if module is not given), at the first event of line line.
break @ [module] line column Set a breakpoint in module module (or in the
current module if module is not given), at the event closest to line line,
column column.
break @ [module] # character Set a breakpoint in module module at the event
closest to character number character.
break address Set a breakpoint at the code address address.
delete [breakpoint-numbers] Delete the specified breakpoints. Without
argument, all breakpoints are deleted (after asking for confirmation).
info breakpoints Print the list of all breakpoints.
15.6 The call stack
*=*=*=*=*=*=*=*=*=*=*
Each time the program performs a function application, it saves the location
of the application (the return address) in a block of data called a stack
frame. The frame also contains the local variables of the caller function. All
the frames are allocated in a region of memory called the call stack. The
command backtrace (or bt) displays parts of the call stack.
At any time, one of the stack frames is ``selected'' by the debugger; several
debugger commands refer implicitly to the selected frame. In particular,
whenever you ask the debugger for the value of a local variable, the value is
found in the selected frame. The commands frame, up and down select whichever
frame you are interested in.
When the program stops, the debugger automatically selects the currently
executing frame and describes it briefly as the frame command does.
frame Describe the currently selected stack frame.
frame frame-number Select a stack frame by number and describe it. The frame
currently executing when the program stopped has number 0; its caller has
number 1; and so on up the call stack.
backtrace [count], bt [count] Print the call stack. This is useful to see
which sequence of function calls led to the currently executing frame. With
a positive argument, print only the innermost count frames. With a negative
argument, print only the outermost -count frames.
up [count] Select and display the stack frame just ``above'' the selected
frame, that is, the frame that called the selected frame. An argument says
how many frames to go up.
down [count] Select and display the stack frame just ``below'' the selected
frame, that is, the frame that was called by the selected frame. An argument
says how many frames to go down.
15.7 Examining variable values
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
The debugger can print the current value of simple expressions. The
expressions can involve program variables: all the identifiers that are in
scope at the selected program point can be accessed.
Expressions that can be printed are a subset of Objective Caml expressions,
as described by the following grammar:
expr ::= lowercase-ident
| { capitalized-ident . } lowercase-ident
| *
| $ integer
| expr . lowercase-ident
| expr .( integer )
| expr .[ integer ]
| ! expr
| ( expr )
The first two cases refer to a value identifier, either unqualified or
qualified by the path to the structure that define it. * refers to the result
just computed (typically, the value of a function application), and is valid
only if the selected event is an ``after'' event (typically, a function
application). $ integer refer to a previously printed value. The remaining four
forms select part of an expression: respectively, a record field, an array
element, a string element, and the current contents of a reference.
print variables Print the values of the given variables. print can be
abbreviated as p.
display variables Same as print, but limit the depth of printing to 1. Useful
to browse large data structures without printing them in full. display can
be abbreviated as d.
When printing a complex expression, a name of the form $integer is
automatically assigned to its value. Such names are also assigned to parts of
the value that cannot be printed because the maximal printing depth is
exceeded. Named values can be printed later on with the commands p $integer or
d $integer. Named values are valid only as long as the program is stopped. They
are forgotten as soon as the program resumes execution.
set print_depth d Limit the printing of values to a maximal depth of d.
set print_length l Limit the printing of values to at most l nodes printed.
15.8 Controlling the debugger
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
15.8.1 Setting the program name and arguments
===============================================
set program file Set the program name to file.
set arguments arguments Give arguments as command-line arguments for the
program.
A shell is used to pass the arguments to the debugged program. You can
therefore use wildcards, shell variables, and file redirections inside the
arguments. To debug programs that read from standard input, it is recommended
to redirect their input from a file (using set arguments < input-file),
otherwise input to the program and input to the debugger are not properly
separated, and inputs are not properly replayed when running the program
backwards.
15.8.2 How programs are loaded
================================
The loadingmode variable controls how the program is executed.
set loadingmode direct The program is run directly by the debugger. This is
the default mode.
set loadingmode runtime The debugger execute the Objective Caml runtime
camlrun on the program. Rarely useful; moreover it prevents the debugging of
programs compiled in ``custom runtime'' mode.
set loadingmode manual The user starts manually the program, when asked by
the debugger. Allows remote debugging (see section 15.8.6).
15.8.3 Search path for files
==============================
The debugger searches for source files and compiled interface files in a list
of directories, the search path. The search path initially contains the current
directory . and the standard library directory. The directory command adds
directories to the path.
Whenever the search path is modified, the debugger will clear any information
it may have cached about the files.
directory directorynames Add the given directories to the search path. These
directories are added at the front, and will therefore be searched first.
directory Reset the search path. This requires confirmation.
15.8.4 Working directory
==========================
Each time a program is started in the debugger, it inherits its working
directory from the current working directory of the debugger. This working
directory is initially whatever it inherited from its parent process (typically
the shell), but you can specify a new working directory in the debugger with
the cd command or the -cd command-line option.
cd directory Set the working directory for camldebug to directory.
pwd Print the working directory for camldebug.
15.8.5 Turning reverse execution on and off
=============================================
In some cases, you may want to turn reverse execution off. This speeds up the
program execution, and is also sometimes useful for interactive programs.
Normally, the debugger takes checkpoints of the program state from time to
time. That is, it makes a copy of the current state of the program (using the
Unix system call fork). If the variable checkpoints is set to off, the debugger
will not take any checkpoints.
set checkpoints on/off Select whether the debugger makes checkpoints or not.
15.8.6 Communication between the debugger and the program
===========================================================
The debugger communicate with the program being debugged through a Unix
socket. You may need to change the socket name, for example if you need to run
the debugger on a machine and your program on another.
set socket socket Use socket for communication with the program. socket can
be either a file name, or an Internet port specification host:port, where
host is a host name or an Internet address in dot notation, and port is a
port number on the host.
On the debugged program side, the socket name is passed either by the -D
command line option to camlrun, or through the CAML_DEBUG_SOCKET environment
variable.
15.8.7 Fine-tuning the debugger
=================================
Several variables enables to fine-tune the debugger. Reasonable defaults are
provided, and you should normally not have to change them.
set processcount count Set the maximum number of checkpoints to count. More
checkpoints facilitate going far back in time, but use more memory and
create more Unix processes.
As checkpointing is quite expensive, it must not be done too often. On the
other hand, backward execution is faster when checkpoints are taken more often.
In particular, backward single-stepping is more responsive when many
checkpoints have been taken just before the current time. To fine-tune the
checkpointing strategy, the debugger does not take checkpoints at the same
frequency for long displacements (e.g. run) and small ones (e.g. step). The two
variables bigstep and smallstep contain the number of events between two
checkpoints in each case.
set bigstep count Set the number of events between two checkpoints for long
displacements.
set smallstep count Set the number of events between two checkpoints for
small displacements.
The following commands display information on checkpoints and events:
info checkpoints Print a list of checkpoints.
info events [module] Print the list of events in the given module (the
current module, by default).
15.8.8 User-defined printers
==============================
Just as in the toplevel system (section 9.2), the user can register functions
for printing values of certain types. For technical reasons, the debugger
cannot call printing functions that reside in the program being debugged. The
code for the printing functions must therefore be loaded explicitly in the
debugger.
load_printer "file-name" Load in the debugger the indicated .cmo or .cma
object file. The file is loaded in an environment consisting only of the
Objective Caml standard library plus the definitions provided by object
files previously loaded using load_printer. If this file depends on other
object files not yet loaded, the debugger automatically loads them if it is
able to find them in the search path. The loaded file does not have direct
access to the modules of the program being debugged.
install_printer printer-name Register the function named printer-name (a
value path) as a printer for objects whose types match the argument type of
the function. That is, the debugger will call printer-name when it has such
an object to print. The printing function printer-name must use the Format
library module to produce its output, otherwise its output will not be
correctly located in the values printed by the toplevel loop.
The value path printer-name must refer to one of the functions defined by the
object files loaded using load_printer. It cannot reference the functions of
the program being debugged.
remove_printer printer-name Remove the named function from the table of value
printers.
15.9 Miscellaneous commands
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
list [module] [beginning] [end] List the source of module module, from line
number beginning to line number end. By default, 20 lines of the current
module are displayed, starting 10 lines before the current position.
source filename Read debugger commands from the script filename.
15.10 Running the debugger under Emacs
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
The most user-friendly way to use the debugger is to run it under Emacs. See
the file emacs/README in the distribution for information on how to load the
Emacs Lisp files for Caml support.
The Caml debugger is started under Emacs by the command M-x camldebug, with
argument the name of the executable file progname to debug. Communication with
the debugger takes place in an Emacs buffer named *camldebug-progname*. The
editing and history facilities of Shell mode are available for interacting with
the debugger.
In addition, Emacs displays the source files containing the current event
(the current position in the program execution) and highlights the location of
the event. This display is updated synchronously with the debugger action.
The following bindings for the most common debugger commands are available in
the *camldebug-progname* buffer:
C-c C-s (command step): execute the program one step forward.
C-c C-k (command backstep): execute the program one step backward.
C-c C-n (command next): execute the program one step forward, skipping over
function calls.
Middle mouse button (command display): display named value. $n under mouse
cursor (support incremental browsing of large data structures).
C-c C-p (command print): print value of identifier at point.
C-c C-d (command display): display value of identifier at point.
C-c C-r (command run): execute the program forward to next breakpoint.
C-c C-v (command reverse): execute the program backward to latest breakpoint.
C-c C-l (command last): go back one step in the command history.
C-c C-t (command backtrace): display backtrace of function calls.
C-c C-f (command finish): run forward till the current function returns.
C-c < (command up): select the stack frame below the current frame.
C-c > (command down): select the stack frame above the current frame.
In all buffers in Caml editing mode, the following debugger commands are also
available:
C-x C-a C-b (command break): set a breakpoint at event closest to point
C-x C-a C-p (command print): print value of identifier at point
C-x C-a C-d (command display): display value of identifier at point
Chapter 16 Profiling (ocamlprof)
************************************
This chapter describes how the execution of Objective Caml programs can be
profiled, by recording how many times functions are called, branches of
conditionals are taken, ...
16.1 Compiling for profiling
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Before profiling an execution, the program must be compiled in profiling
mode, using the ocamlcp front-end to the ocamlc compiler (see chapter 8). When
compiling modules separately, ocamlcp must be used when compiling the modules
(production of .cmo files), and can also be used (though this is not strictly
necessary) when linking them together.
To make sure your programs can be compiled in profiling mode, avoid using any
identifier that begins with __ocaml_prof.
The amount of profiling information can be controlled through the -p option
to ocamlcp, followed by one or several letters indicating which parts of the
program should be profiled:
a all options
f function calls : a count point is set at the beginning of function bodies
i if ...then ...else ... : count points are set in both then branch and else
branch
l while, for loops: a count point is set at the beginning of the loop body
m match branches: a count point is set at the beginning of the body of each
branch
t try ...with ... branches: a count point is set at the beginning of the body
of each branch
For instance, compiling with ocamlcp -p film profiles function calls,
if...then...else..., loops and pattern matching.
Calling ocamlcp without the -p option defaults to -p fm, meaning that only
function calls and pattern matching are profiled.
Note: Due to the implementation of streams and stream patterns as syntactic
sugar, it is hard to predict what parts of stream expressions and patterns will
be profiled by a given flag. To profile a program with streams, we recommend
using ocamlcp -p a.
16.2 Profiling an execution
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
Running a bytecode executable file that has been compiled with ocamlcp
records the execution counts for the specified parts of the program and saves
them in a file called ocamlprof.dump in the current directory.
The ocamlprof.dump file is written only if the program terminates normally
(by calling exit or by falling through). It is not written if the program
terminates with an uncaught exception.
If a compatible dump file already exists in the current directory, then the
profiling information is accumulated in this dump file. This allows, for
instance, the profiling of several executions of a program on different inputs.
16.3 Printing profiling information
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
The ocamlprof command produces a source listing of the program modules where
execution counts have been inserted as comments. For instance,
<<
ocamlprof foo.ml
>>
prints the source code for the foo module, with comments indicating how many
times the functions in this module have been called. Naturally, this
information is accurate only if the source file has not been modified since the
profiling execution took place.
The following options are recognized by ocamlprof:
-f dumpfile Specifies an alternate dump file of profiling information
-F string Specifies an additional string to be output with profiling
information. By default, ocamlprof will annotate programs with comments of
the form (* n *) where n is the counter value for a profiling point. With
option -F s, the annotation will be (* sn *).
16.4 Time profiling
*=*=*=*=*=*=*=*=*=*=*
Profiling with ocamlprof only records execution counts, not the actual time
spent into each function. There is currently no way to perform time profiling
on bytecode programs generated by ocamlc.
Native-code programs generated by ocamlopt can be profiled for time and
execution counts using the -p option and the standard Unix profiler gprof. Just
add the -p option when compiling and linking the program:
<<
ocamlopt -o myprog -p other-options files
./myprog
gprof myprog
>>
Caml function names in the output of gprof have the following format:
<<
Module-name_function-name_unique-number
>>
Other functions shown are either parts of the Caml run-time system or
external C functions linked with the program.
The output of gprof is described in the Unix manual page for gprof(1). It
generally consists of two parts: a ``flat'' profile showing the time spent in
each function and the number of invocation of each function, and a
``hierarchical'' profile based on the call graph. Currently, only the Intel
x86/Linux and Alpha/Digital Unix ports of ocamlopt support the two profiles. On
other platforms, gprof will report only the ``flat'' profile with just time
information. When reading the output of gprof, keep in mind that the
accumulated times computed by gprof are based on heuristics and may not be
exact.
Chapter 17 Interfacing C with Objective Caml
************************************************
This chapter describes how user-defined primitives, written in C, can be
linked with Caml code and called from Caml functions.
17.1 Overview and compilation information
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
17.1.1 Declaring primitives
=============================
User primitives are declared in an implementation file or struct...end module
expression using the external keyword:
<<
external name : type = C-function-name
>>
This defines the value name name as a function with type type that executes
by calling the given C function. For instance, here is how the input primitive
is declared in the standard library module Pervasives:
<<
external input : in_channel -> string -> int -> int -> int
= "input"
>>
Primitives with several arguments are always curried. The C function does not
necessarily have the same name as the ML function.
External functions thus defined can be specified in interface files or
sig...end signatures either as regular values
<<
val name : type
>>
thus hiding their implementation as a C function, or explicitly as
``manifest'' external functions
<<
external name : type = C-function-name
>>
The latter is slightly more efficient, as it allows clients of the module to
call directly the C function instead of going through the corresponding Caml
function.
The arity (number of arguments) of a primitive is automatically determined
from its Caml type in the external declaration, by counting the number of
function arrows in the type. For instance, input above has arity 4, and the
input C function is called with four arguments. Similarly,
<<
external input2 : in_channel * string * int * int -> int = "input2"
>>
has arity 1, and the input2 C function receives one argument (which is a
quadruple of Caml values).
Type abbreviations are not expanded when determining the arity of a
primitive. For instance,
<<
type int_endo = int -> int
external f : int_endo -> int_endo = "f"
external g : (int -> int) -> (int -> int) = "f"
>>
f has arity 1, but g has arity 2. This allows a primitive to return a
functional value (as in the f example above): just remember to name the
functional return type in a type abbreviation.
17.1.2 Implementing primitives
================================
User primitives with arity n <= 5 are implemented by C functions that take n
arguments of type value, and return a result of type value. The type value is
the type of the representations for Caml values. It encodes objects of several
base types (integers, floating-point numbers, strings, ...), as well as Caml
data structures. The type value and the associated conversion functions and
macros are described in details below. For instance, here is the declaration
for the C function implementing the input primitive:
<<
value input(value channel, value buffer, value offset, value length)
{
...
}
>>
When the primitive function is applied in a Caml program, the C function is
called with the values of the expressions to which the primitive is applied as
arguments. The value returned by the function is passed back to the Caml
program as the result of the function application.
User primitives with arity greater than 5 should be implemented by two C
functions. The first function, to be used in conjunction with the bytecode
compiler ocamlc, receives two arguments: a pointer to an array of Caml values
(the values for the arguments), and an integer which is the number of arguments
provided. The other function, to be used in conjunction with the native-code
compiler ocamlopt, takes its arguments directly. For instance, here are the two
C functions for the 7-argument primitive Nat.add_nat:
<<
value add_nat_native(value nat1, value ofs1, value len1,
value nat2, value ofs2, value len2,
value carry_in)
{
...
}
value add_nat_bytecode(value * argv, int argn)
{
return add_nat_native(argv[0], argv[1], argv[2], argv[3],
argv[4], argv[5], argv[6]);
}
>>
The names of the two C functions must be given in the primitive declaration,
as follows:
<<
external name : type =
bytecode-C-function-name native-code-C-function-name
>>
For instance, in the case of add_nat, the declaration is:
<<
external add_nat: nat -> int -> int -> nat -> int -> int -> int ->
int
= "add_nat_bytecode" "add_nat_native"
>>
Implementing a user primitive is actually two separate tasks: on the one
hand, decoding the arguments to extract C values from the given Caml values,
and encoding the return value as a Caml value; on the other hand, actually
computing the result from the arguments. Except for very simple primitives, it
is often preferable to have two distinct C functions to implement these two
tasks. The first function actually implements the primitive, taking native C
values as arguments and returning a native C value. The second function, often
called the ``stub code'', is a simple wrapper around the first function that
converts its arguments from Caml values to C values, call the first function,
and convert the returned C value to Caml value. For instance, here is the stub
code for the input primitive:
<<
value input(value channel, value buffer, value offset, value length)
{
return Val_long(getblock((struct channel *) channel,
&Byte(buffer, Long_val(offset)),
Long_val(length)));
}
>>
(Here, Val_long, Long_val and so on are conversion macros for the type value,
that will be described later.) The hard work is performed by the function
getblock, which is declared as:
<<
long getblock(struct channel * channel, char * p, long n)
{
...
}
>>
To write C code that operates on Objective Caml values, the following include
files are provided:
----------------------------------------------------
| Include file | Provides |
----------------------------------------------------
|caml/mlvalues.h|definition of the value type, and |
| |conversion macros |
|caml/alloc.h |allocation functions (to create |
| |structured Caml objects) |
|caml/memory.h |miscellaneous memory-related |
| |functions and macros (for GC |
| |interface, in-place modification |
| |of structures, etc). |
|caml/fail.h |functions for raising exceptions |
| |(see section 17.4.5) |
|caml/callback.h|callback from C to Caml (see |
| |section 17.7). |
|caml/custom.h |operations on custom blocks (see |
| |section 17.9). |
|caml/intext.h |operations for writing |
| |user-defined serialization and |
| |deserialization functions for |
| |custom blocks (see section 17.9). |
----------------------------------------------------
These files reside in the caml/ subdirectory of the Objective Caml standard
library directory (usually /usr/local/lib/ocaml).
17.1.3 Linking C code with Caml code
======================================
The Objective Caml runtime system comprises three main parts: the bytecode
interpreter, the memory manager, and a set of C functions that implement the
primitive operations. Some bytecode instructions are provided to call these C
functions, designated by their offset in a table of functions (the table of
primitives).
In the default mode, the Caml linker produces bytecode for the standard
runtime system, with a standard set of primitives. References to primitives
that are not in this standard set result in the ``unavailable C primitive''
error.
In the ``custom runtime'' mode, the Caml linker scans the object files and
determines the set of required primitives. Then, it builds a suitable runtime
system, by calling the native code linker with:
- the table of the required primitives;
- a library that provides the bytecode interpreter, the memory manager, and
the standard primitives;
- libraries and object code files (.o files) mentioned on the command line for
the Caml linker, that provide implementations for the user's primitives.
This builds a runtime system with the required primitives. The Caml linker
generates bytecode for this custom runtime system. The bytecode is appended to
the end of the custom runtime system, so that it will be automatically executed
when the output file (custom runtime + bytecode) is launched.
To link in ``custom runtime'' mode, execute the ocamlc command with:
- the -custom option;
- the names of the desired Caml object files (.cmo and .cma files) ;
- the names of the C object files and libraries (.o and .a files) that
implement the required primitives. Under Unix and Windows, a library named
libname.a residing in one of the standard library directories can also be
specified as -cclib -lname.
If you are using the native-code compiler ocamlopt, the -custom flag is not
needed, as the final linking phase of ocamlopt always builds a standalone
executable. To build a mixed Caml/C executable, execute the ocamlopt command
with:
- the names of the desired Caml native object files (.cmx and .cmxa files);
- the names of the C object files and libraries (.o and .a files) that
implement the required primitives.
Starting with OCaml 3.00, it is possible to record the -custom option as well
as the names of C libraries in a Caml library file .cma or .cmxa. For instance,
consider a Caml library mylib.cma, built from the Caml object files a.cmo and
b.cmo, which reference C code in libmylib.a. If the library is built as
follows:
<<
ocamlc -a -o mylib.cma -custom a.cmo b.cmo -cclib -lmylib
>>
users of the library can simply link with mylib.cma:
<<
ocamlc -o myprog mylib.cma ...
>>
and the system will automatically add the -custom and -cclib -lmylib
options, achieving the same effect as
<<
ocamlc -o myprog -custom a.cmo b.cmo ... -cclib -lmylib
>>
The alternative, of course, is to build the library without extra options:
<<
ocamlc -a -o mylib.cma a.cmo b.cmo
>>
and then ask users to provide the -custom and -cclib -lmylib options
themselves at link-time:
<<
ocamlc -o myprog -custom mylib.cma ... -cclib -lmylib
>>
The former alternative is more convenient for the final users of the
library, however.
17.1.4 Building standalone custom runtime systems
===================================================
It is sometimes inconvenient to build a custom runtime system each time Caml
code is linked with C libraries, like ocamlc -custom does. For one thing, the
building of the runtime system is slow on some systems (that have bad linkers
or slow remote file systems); for another thing, the platform-independence of
bytecode files is lost, forcing to perform one ocamlc -custom link per platform
of interest.
An alternative to ocamlc -custom is to build separately a custom runtime
system integrating the desired C libraries, then generate ``pure'' bytecode
executables (not containing their own runtime system) that can run on this
custom runtime. This is achieved by the -make_runtime and -use_runtime flags to
ocamlc. For example, to build a custom runtime system integrating the C parts
of the ``unix'' and ``threads'' libraries, do:
<<
ocamlc -make-runtime -o /home/me/ocamlunixrun unix.cma threads.cma
>>
To generate a bytecode executable that runs on this runtime system, do:
<<
ocamlc -use-runtime /home/me/ocamlunixrun -o myprog \
unix.cma threads.cma your .cmo and .cma files
>>
The bytecode executable myprog can then be launched as usual: myprog args or
/home/me/ocamlunixrun myprog args.
Notice that the bytecode libraries unix.cma and threads.cma must be given
twice: when building the runtime system (so that ocamlc knows which C
primitives are required) and also when building the bytecode executable (so
that the bytecode from unix.cma and threads.cma is actually linked in).
17.2 The value type
*=*=*=*=*=*=*=*=*=*=*
All Caml objects are represented by the C type value, defined in the include
file caml/mlvalues.h, along with macros to manipulate values of that type. An
object of type value is either:
- an unboxed integer;
- a pointer to a block inside the heap (such as the blocks allocated through
one of the `alloc_*' functions below);
- a pointer to an object outside the heap (e.g., a pointer to a block
allocated by malloc, or to a C variable).
17.2.1 Integer values
=======================
Integer values encode 31-bit signed integers (63-bit on 64-bit
architectures). They are unboxed (unallocated).
17.2.2 Blocks
===============
Blocks in the heap are garbage-collected, and therefore have strict structure
constraints. Each block includes a header containing the size of the block (in
words), and the tag of the block. The tag governs how the contents of the
blocks are structured. A tag lower than No_scan_tag indicates a structured
block, containing well-formed values, which is recursively traversed by the
garbage collector. A tag greater than or equal to No_scan_tag indicates a raw
block, whose contents are not scanned by the garbage collector. For the
benefits of ad-hoc polymorphic primitives such as equality and structured
input-output, structured and raw blocks are further classified according to
their tags as follows:
-------------------------------------------------
| Tag | Contents of the block |
-------------------------------------------------
|0 to No_scan_tag-1|A structured block (an array|
| |of Caml objects). Each field|
| |is a value. |
|Closure_tag |A closure representing a |
| |functional value. The first |
| |word is a pointer to a piece|
| |of code, the remaining words|
| |are value containing the |
| |environment. |
|String_tag |A character string. |
|Double_tag |A double-precision |
| |floating-point number. |
|Double_array_tag |An array or record of |
| |double-precision |
| |floating-point numbers. |
|Abstract_tag |A block representing an |
| |abstract datatype. |
|Custom_tag |A block representing an |
| |abstract datatype with |
| |user-defined finalization, |
| |comparison, hashing, |
| |serialization and |
| |deserialization functions |
| |atttached. |
-------------------------------------------------
17.2.3 Pointers outside the heap
==================================
Any word-aligned pointer to an address outside the heap can be safely cast to
and from the type value. This includes pointers returned by malloc, and
pointers to C variables (of size at least one word) obtained with the `&'
operator.
Caution: if a pointer returned by malloc is cast to the type value and
returned to Caml, explicit deallocation of the pointer using free is
potentially dangerous, because the pointer may still be accessible from the
Caml world. Worse, the memory space deallocated by free can later be
reallocated as part of the Caml heap; the pointer, formerly pointing outside
the Caml heap, now points inside the Caml heap, and this can confuse the
garbage collector. To avoid these problems, it is preferable to wrap the
pointer in a Caml block with tag Abstract_tag or Custom_tag.
17.3 Representation of Caml data types
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This section describes how Caml data types are encoded in the value type.
17.3.1 Atomic types
=====================
------------------------------------------------
|Caml type| Encoding |
------------------------------------------------
|int |Unboxed integer values. |
|char |Unboxed integer values (ASCII code).|
|float |Blocks with tag Double_tag. |
|string |Blocks with tag String_tag. |
|int32 |Blocks with tag Custom_tag. |
|int64 |Blocks with tag Custom_tag. |
|nativeint|Blocks with tag Custom_tag. |
------------------------------------------------
17.3.2 Tuples and records
===========================
Tuples are represented by pointers to blocks, with tag 0.
Records are also represented by zero-tagged blocks. The ordering of labels in
the record type declaration determines the layout of the record fields: the
value associated to the label declared first is stored in field 0 of the block,
the value associated to the label declared next goes in field 1, and so on.
As an optimization, records whose fields all have static type float are
represented as arrays of floating-point numbers, with tag Double_array_tag.
(See the section below on arrays.)
17.3.3 Arrays
===============
Arrays of integers and pointers are represented like tuples, that is, as
pointers to blocks tagged 0. They are accessed with the Field macro for reading
and the modify function for writing.
Arrays of floating-point numbers (type float array) have a special, unboxed,
more efficient representation. These arrays are represented by pointers to
blocks with tag Double_array_tag. They should be accessed with the Double_field
and Store_double_field macros.
17.3.4 Concrete types
=======================
Constructed terms are represented either by unboxed integers (for constant
constructors) or by blocks whose tag encode the constructor (for non-constant
constructors). The constant constructors and the non-constant constructors for
a given concrete type are numbered separately, starting from 0, in the order in
which they appear in the concrete type declaration. Constant constructors are
represented by unboxed integers equal to the constructor number. Non-constant
constructors declared with a n-tuple as argument are represented by a block of
size n, tagged with the constructor number; the n fields contain the components
of its tuple argument. Other non-constant constructors are represented by a
block of size 1, tagged with the constructor number; the field 0 contains the
value of the constructor argument. Example:
------------------------------------------
|Constructed term| Representation |
------------------------------------------
|() |Val_int(0) |
|false |Val_int(0) |
|true |Val_int(1) |
|[] |Val_int(0) |
|h::t |Block with size = 2 and|
| |tag = 0; first field |
| |contains h, second |
| |field t |
------------------------------------------
As a convenience, caml/mlvalues.h defines the macros Val_unit, Val_false and
Val_true to refer to (), false and true.
17.3.5 Objects
================
Objects are represented as zero-tagged blocks. The first field of the block
refers to the object class and associated method suite, in a format that cannot
easily be exploited from C. The remaining fields of the object contain the
values of the instance variables of the object. Instance variables are stored
in the order in which they appear in the class definition (taking inherited
classes into account).
17.3.6 Variants
=================
Like constructed terms, values of variant types are represented either as
integers (for variants without arguments), or as blocks (for variants with an
argument). Unlike constructed terms, variant constructors are not numbered
starting from 0, but identified by a hash value (a Caml integer), as computed
by the C function hash_variant (declared in <caml/mlvalues.h>): the hash value
for a variant constructor named, say, VConstr is hash_value("VConstr").
The variant value `VConstr is represented by hash_value("VConstr"). The
variant value `VConstr(v) is represented by a block of size 2 and tag 0, with
field number 0 containing hash_value("VConstr") and field number 1 containing
v.
Unlike constructed values, variant values taking several arguments are not
flattened. That is, `VConstr(v, v') is represented by a block of size 2, whose
field number 1 contains the representation of the pair (v, v'), but not as a
block of size 3 containing v and v' in fields 1 and 2.
17.4 Operations on values
*=*=*=*=*=*=*=*=*=*=*=*=*=*
17.4.1 Kind tests
===================
- Is_long(v) is true if value v is an immediate integer, false otherwise
- Is_block(v) is true if value v is a pointer to a block, and false if it is
an immediate integer.
17.4.2 Operations on integers
===============================
- Val_long(l) returns the value encoding the long int l.
- Long_val(v) returns the long int encoded in value v.
- Val_int(i) returns the value encoding the int i.
- Int_val(v) returns the int encoded in value v.
- Val_bool(x) returns the Caml boolean representing the truth value of the C
integer x.
- Bool_val(v) returns 0 if v is the Caml boolean false, 1 if v is true.
- Val_true, Val_false represent the Caml booleans true and false.
17.4.3 Accessing blocks
=========================
- Wosize_val(v) returns the size of the block v, in words, excluding the
header.
- Tag_val(v) returns the tag of the block v.
- Field(v, n) returns the value contained in the n^th field of the structured
block v. Fields are numbered from 0 to Wosize_val(v)-1.
- Store_field(b, n, v) stores the value v in the field number n of value b,
which must be a structured block.
- Code_val(v) returns the code part of the closure v.
- string_length(v) returns the length (number of characters) of the string v.
- Byte(v, n) returns the n^th character of the string v, with type char.
Characters are numbered from 0 to string_length(v)-1.
- Byte_u(v, n) returns the n^th character of the string v, with type unsigned
char. Characters are numbered from 0 to string_length(v)-1.
- String_val(v) returns a pointer to the first byte of the string v, with type
char *. This pointer is a valid C string: there is a null character after
the last character in the string. However, Caml strings can contain embedded
null characters, that will confuse the usual C functions over strings.
- Double_val(v) returns the floating-point number contained in value v, with
type double.
- Double_field(v, n) returns the n^th element of the array of floating-point
numbers v (a block tagged Double_array_tag).
- Store_double_field(v, n, d) stores the double precision floating-point
number d in the n^th element of the array of floating-point numbers v.
- Data_custom_val(v) returns a pointer to the data part of the custom block v.
This pointer has type void * and must be cast to the type of the data
contained in the custom block.
- Int32_val(v) returns the 32-bit integer contained in the int32 v.
- Int64_val(v) returns the 64-bit integer contained in the int64 v.
- Nativeint_val(v) returns the long integer contained in the nativeint v.
The expressions Field(v, n), Byte(v, n) and Byte_u(v, n) are valid l-values.
Hence, they can be assigned to, resulting in an in-place modification of value
v. Assigning directly to Field(v, n) must be done with care to avoid confusing
the garbage collector (see below).
17.4.4 Allocating blocks
==========================
Simple interface
-----------------
- Atom(t) returns an ``atom'' (zero-sized block) with tag t. Zero-sized blocks
are preallocated outside of the heap. It is incorrect to try and allocate a
zero-sized block using the functions below. For instance, Atom(0) represents
the empty array.
- alloc(n, t) returns a fresh block of size n with tag t. If t is less than
No_scan_tag, then the fields of the block are initialized with a valid value
in order to satisfy the GC constraints.
- alloc_tuple(n) returns a fresh block of size n words, with tag 0.
- alloc_string(n) returns a string value of length n characters. The string
initially contains garbage.
- copy_string(s) returns a string value containing a copy of the
null-terminated C string s (a char *).
- copy_double(d) returns a floating-point value initialized with the double d.
- copy_int32(i), copy_int64(i) and copy_nativeint(i) return a value of Caml
type int32, int64 and nativeint, respectively, initialized with the integer
i.
- alloc_array(f, a) allocates an array of values, calling function f over each
element of the input array a to transform it into a value. The array a is an
array of pointers terminated by the null pointer. The function f receives
each pointer as argument, and returns a value. The zero-tagged block
returned by alloc_array(f, a) is filled with the values returned by the
successive calls to f. (This function must not be used to build an array of
floating-point numbers.)
- copy_string_array(p) allocates an array of strings, copied from the pointer
to a string array p (a `char **').
Low-level interface
--------------------
The following functions are slightly more efficient than alloc, but also much
more difficult to use.
From the standpoint of the allocation functions, blocks are divided according
to their size as zero-sized blocks, small blocks (with size less than or equal
to `Max_young_wosize'), and large blocks (with size greater than
`Max_young_wosize'). The constant `Max_young_wosize' is declared in the include
file mlvalues.h. It is guaranteed to be at least 64 (words), so that any block
with constant size less than or equal to 64 can be assumed to be small. For
blocks whose size is computed at run-time, the size must be compared against
`Max_young_wosize' to determine the correct allocation procedure.
- alloc_small(n, t) returns a fresh small block of size n <= Max_young_wosize
words, with tag t. If this block is a structured block (i.e. if t <
No_scan_tag), then the fields of the block (initially containing garbage)
must be initialized with legal values (using direct assignment to the fields
of the block) before the next allocation.
- alloc_shr(n, t) returns a fresh block of size n, with tag t. The size of
the block can be greater than `Max_young_wosize'. (It can also be smaller,
but in this case it is more efficient to call alloc_small instead of
alloc_shr.) If this block is a structured block (i.e. if t < No_scan_tag),
then the fields of the block (initially containing garbage) must be
initialized with legal values (using the initialize function described
below) before the next allocation.
17.4.5 Raising exceptions
===========================
Two functions are provided to raise two standard exceptions:
- failwith(s), where s is a null-terminated C string (with type `char *'),
raises exception Failure with argument s.
- invalid_argument(s), where s is a null-terminated C string (with type `char
*'), raises exception Invalid_argument with argument s.
Raising arbitrary exceptions from C is more delicate: the exception
identifier is dynamically allocated by the Caml program, and therefore must be
communicated to the C function using the registration facility described below
in section 17.7.3. Once the exception identifier is recovered in C, the
following functions actually raise the exception:
- raise_constant(id) raises the exception id with no argument;
- raise_with_arg(id, v) raises the exception id with the Caml value v as
argument;
- raise_with_string(id, s), where s is a null-terminated C string, raises the
exception id with a copy of the C string s as argument.
17.5 Living in harmony with the garbage collector
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
Unused blocks in the heap are automatically reclaimed by the garbage
collector. This requires some cooperation from C code that manipulates
heap-allocated blocks.
17.5.1 Simple interface
=========================
All the macros described in this section are declared in the memory.h header
file.
Rule 1 A function that has parameters or local variables of type value must
begin with a call to one of the CAMLparam macros and return with CAMLreturn or
CAMLreturn0.
There are six CAMLparam macros: CAMLparam0 to CAMLparam5, which take zero to
five arguments respectively. If your function has fewer than 5 parameters of
type value, use the corresponding macros with these parameters as arguments. If
your function has more than 5 parameters of type value, use CAMLparam5 with
five of these parameters, and use one or more calls to the CAMLxparam macros
for the remaining parameters (CAMLxparam0 to CAMLxparam5).
The macros CAMLreturn and CAMLreturn0 are used to replace the C keyword
return. Every occurence of return x must be replaced by CAMLreturn (x), every
occurence of return without argument must be replaced by CAMLreturn0. If your C
function is a procedure (i.e. if it returns void), you must insert CAMLreturn0
at the end (to replace C's implicit return).
Note: some C compilers give bogus warnings about unused variables
caml__dummy_xxx at each use of CAMLparam and CAMLlocal. You should ignore them.
Example:
<<
void foo (value v1, value v2, value v3)
{
CAMLparam3 (v1, v2, v3);
...
CAMLreturn0;
}
>>
Note: if your function is a primitive with more than 5 arguments for use with
the byte-code runtime, its arguments are not values and must not be declared
(they have types value * and int).
Rule 2 Local variables of type value must be declared with one of the
CAMLlocal macros. Arrays of values are declared with CAMLlocalN.
The macros CAMLlocal1 to CAMLlocal5 declare and initialize one to five local
variables of type value. The variable names are given as arguments to the
macros. CAMLlocalN(x, n) declares and initializes a local variable of type
value [n]. You can use several calls to these macros if you have more than 5
local variables. You can also use them in nested C blocks within the function.
Example:
<<
value bar (value v1, value v2, value v3)
{
CAMLparam3 (v1, v2, v3);
CAMLlocal1 (result);
result = alloc (3, 0);
...
CAMLreturn (result);
}
>>
Rule 3 Assignments to the fields of structured blocks must be done with the
Store_field macro. Other assignments must not use Store_field.
Store_field (b, n, v) stores the value v in the field number n of value b,
which must be a block (i.e. Is_block(b) must be true).
Example:
<<
value bar (value v1, value v2, value v3)
{
CAMLparam3 (v1, v2, v3);
CAMLlocal1 (result);
result = alloc (3, 0);
Store_field (result, 0, v1);
Store_field (result, 1, v2);
Store_field (result, 2, v3);
CAMLreturn (result);
}
>>
Rule 4 Global variables containing values must be registered with the
garbage collector using the register_global_root function.
Registration of a global variable v is achieved by calling
register_global_root(&v) just before a valid value is stored in v for the first
time.
A registered global variable v can be un-registered by calling
remove_global_root(&v).
Note: The CAML macros use identifiers (local variables, type identifiers,
structure tags) that start with caml__. Do not use any identifier starting with
caml__ in your programs.
17.5.2 Low-level interface
============================
We now give the GC rules corresponding to the low-level allocation functions
alloc_small and alloc_shr. You can ignore those rules if you stick to the
simplified allocation function alloc.
Rule 5 After a structured block (a block with tag less than No_scan_tag) is
allocated with the low-level functions, all fields of this block must be filled
with well-formed values before the next allocation operation. If the block has
been allocated with alloc_small, filling is performed by direct assignment to
the fields of the block:
<<
Field(v, n) = v_n;
>>
If the block has been allocated with alloc_shr, filling is performed through
the initialize function:
<<
initialize(&Field(v, n), v_n);
>>
The next allocation can trigger a garbage collection. The garbage collector
assumes that all structured blocks contain well-formed values. Newly created
blocks contain random data, which generally do not represent well-formed
values.
If you really need to allocate before the fields can receive their final
value, first initialize with a constant value (e.g. Val_unit), then allocate,
then modify the fields with the correct value (see rule 6).
Rule 6 Direct assignment to a field of a block, as in
<<
Field(v, n) = w;
>>
is safe only if v is a block newly allocated by alloc_small; that is, if no
allocation took place between the allocation of v and the assignment to the
field. In all other cases, never assign directly. If the block has just been
allocated by alloc_shr, use initialize to assign a value to a field for the
first time:
<<
initialize(&Field(v, n), w);
>>
Otherwise, you are updating a field that previously contained a well-formed
value; then, call the modify function:
<<
modify(&Field(v, n), w);
>>
To illustrate the rules above, here is a C function that builds and returns a
list containing the two integers given as parameters. First, we write it using
the simplified allocation functions:
<<
value alloc_list_int(int i1, int i2)
{
CAMLparam0;
CAMLlocal2 (result, r);
r = alloc(2, 0); /* Allocate a cons cell */
Store_field(r, 0, Val_int(i2)); /* car = the integer i2 */
Store_field(r, 1, Val_int(0)); /* cdr = the empty list [] */
result = alloc(2, 0); /* Allocate the other cons cell */
Store_field(result, 0, Val_int(i1)); /* car = the integer i1 */
Store_field(result, 1, r); /* cdr = the first cons cell */
CAMLreturn (result);
}
>>
Here, the registering of result is not strictly needed, because no allocation
takes place after it gets its value, but it's easier and safer to simply
register all the local variables that have type value.
Here is the same function written using the low-level allocation functions.
We notice that the cons cells are small blocks and can be allocated with
alloc_small, and filled by direct assignments on their fields.
<<
value alloc_list_int(int i1, int i2)
{
CAMLparam0;
CAMLlocal2 (result, r);
r = alloc_small(2, 0); /* Allocate a cons cell */
Field(r, 0) = Val_int(i2); /* car = the integer i2 */
Field(r, 1) = Val_int(0); /* cdr = the empty list [] */
result = alloc_small(2, 0); /* Allocate the other cons cell */
Field(result, 0) = Val_int(i1); /* car = the integer i1 */
Field(result, 1) = r; /* cdr = the first cons cell */
CAMLreturn (result);
}
>>
In the two examples above, the list is built bottom-up. Here is an alternate
way, that proceeds top-down. It is less efficient, but illustrates the use of
modify.
<<
value alloc_list_int(int i1, int i2)
{
CAMLparam0;
CAMLlocal2 (tail, r);
r = alloc_small(2, 0); /* Allocate a cons cell */
Field(r, 0) = Val_int(i1); /* car = the integer i1 */
Field(r, 1) = Val_int(0); /* A dummy value
tail = alloc_small(2, 0); /* Allocate the other cons cell */
Field(tail, 0) = Val_int(i2); /* car = the integer i2 */
Field(tail, 1) = Val_int(0); /* cdr = the empty list [] */
modify(&Field(r, 1), tail); /* cdr of the result = tail */
return r;
}
>>
It would be incorrect to perform Field(r, 1) = tail directly, because the
allocation of tail has taken place since r was allocated. tail is not
registered as a root because there is no allocation between the assignment
where it takes its value and the modify statement that uses the value.
17.6 A complete example
*=*=*=*=*=*=*=*=*=*=*=*=*
This section outlines how the functions from the Unix curses library can be
made available to Objective Caml programs. First of all, here is the interface
curses.mli that declares the curses primitives and data types:
<<
type window (* The type "window" remains abstract *)
external initscr: unit -> window = "curses_initscr"
external endwin: unit -> unit = "curses_endwin"
external refresh: unit -> unit = "curses_refresh"
external wrefresh : window -> unit = "curses_wrefresh"
external newwin: int -> int -> int -> int -> window = "curses_newwin"
external mvwin: window -> int -> int -> unit = "curses_mvwin"
external addch: char -> unit = "curses_addch"
external mvwaddch: window -> int -> int -> char -> unit = "curses_mvwaddch"
external addstr: string -> unit = "curses_addstr"
external mvwaddstr: window -> int -> int -> string -> unit =
"curses_mvwaddstr"
(* lots more omitted *)
>>
To compile this interface:
<<
ocamlc -c curses.mli
>>
To implement these functions, we just have to provide the stub code; the core
functions are already implemented in the curses library. The stub code file,
curses.o, looks like:
<<
#include <curses.h>
#include <mlvalues.h>
value curses_initscr(value unit)
{
return (value) initscr(); /* OK to coerce directly from WINDOW * to
value
since that's a block created by malloc()
*/
}
value curses_wrefresh(value win)
{
wrefresh((WINDOW *) win);
return Val_unit;
}
value curses_newwin(value nlines, value ncols, value x0, value y0)
{
return (value) newwin(Int_val(nlines), Int_val(ncols),
Int_val(x0), Int_val(y0));
}
value curses_addch(value c)
{
addch(Int_val(c)); /* Characters are encoded like integers */
return Val_unit;
}
value curses_addstr(value s)
{
addstr(String_val(s));
return Val_unit;
}
/* This goes on for pages. */
>>
The file curses.c can be compiled with:
<<
cc -c -I/usr/local/lib/ocaml curses.c
>>
or, even simpler,
<<
ocamlc -c curses.c
>>
(When passed a .c file, the ocamlc command simply calls the C compiler on
that file, with the right -I option.)
Now, here is a sample Caml program test.ml that uses the curses module:
<<
open Curses
let main_window = initscr () in
let small_window = newwin 10 5 20 10 in
mvwaddstr main_window 10 2 "Hello";
mvwaddstr small_window 4 3 "world";
refresh();
for i = 1 to 100000 do () done;
endwin()
>>
To compile this program, run:
<<
ocamlc -c test.ml
>>
Finally, to link everything together:
<<
ocamlc -custom -o test test.cmo curses.o -cclib -lcurses
>>
(On some machines, you may need to put -cclib -ltermcap or -cclib -lcurses
-cclib -ltermcap instead of -cclib -lcurses.)
17.7 Advanced topic: callbacks from C to Caml
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
So far, we have described how to call C functions from Caml. In this section,
we show how C functions can call Caml functions, either as callbacks (Caml
calls C which calls Caml), or because the main program is written in C.
17.7.1 Applying Caml closures from C
======================================
C functions can apply Caml functional values (closures) to Caml values. The
following functions are provided to perform the applications:
- callback(f, a) applies the functional value f to the value a and return the
value returned by f.
- callback2(f, a, b) applies the functional value f (which is assumed to be a
curried Caml function with two arguments) to a and b.
- callback3(f, a, b, c) applies the functional value f (a curried Caml
function with three arguments) to a, b and c.
- callbackN(f, n, args) applies the functional value f to the n arguments
contained in the array of values args.
If the function f does not return, but raises an exception that escapes the
scope of the application, then this exception is propagated to the next
enclosing Caml code, skipping over the C code. That is, if a Caml function f
calls a C function g that calls back a Caml function h that raises a stray
exception, then the execution of g is interrupted and the exception is
propagated back into f.
If the C code wishes to catch exceptions escaping the Caml function, it can
use the functions callback_exn, callback2_exn, callback3_exn, callbackN_exn.
These functions take the same arguments as their non-_exn counterparts, but
catch escaping exceptions and return them to the C code. The return value v of
the callback*_exn functions must be tested with the macro
Is_exception_result(v). If the macro returns ``false'', no exception occured,
and v is the value returned by the Caml function. If Is_exception_result(v)
returns ``true'', an exception escaped, and its value (the exception
descriptor) can be recovered using Extract_exception(v).
17.7.2 Registering Caml closures for use in C functions
=========================================================
The main difficulty with the callback functions described above is obtaining
a closure to the Caml function to be called. For this purpose, Objective Caml
provides a simple registration mechanism, by which Caml code can register Caml
functions under some global name, and then C code can retrieve the
corresponding closure by this global name.
On the Caml side, registration is performed by evaluating Callback.register n
v. Here, n is the global name (an arbitrary string) and v the Caml value. For
instance:
<<
let f x = print_string "f is applied to "; print_int n; print_newline()
let _ = Callback.register "test function" f
>>
On the C side, a pointer to the value registered under name n is obtained by
calling caml_named_value(n). The returned pointer must then be dereferenced to
recover the actual Caml value. If no value is registered under the name n, the
null pointer is returned. For example, here is a C wrapper that calls the Caml
function f above:
<<
void call_caml_f(int arg)
{
callback(*caml_named_value("test function"), Val_int(arg));
}
>>
The pointer returned by caml_named_value is constant and can safely be cached
in a C variable to avoid repeated name lookups. On the other hand, the value
pointed to can change during garbage collection and must always be recomputed
at the point of use. Here is a more efficient variant of call_caml_f above that
calls caml_named_value only once:
<<
void call_caml_f(int arg)
{
static value * closure_f = NULL;
if (closure_f == NULL) {
/* First time around, look up by name */
closure_f = caml_named_value("test function");
}
callback(*closure_f, Val_int(arg));
}
>>
17.7.3 Registering Caml exceptions for use in C functions
===========================================================
The registration mechanism described above can also be used to communicate
exception identifiers from Caml to C. The Caml code registers the exception by
evaluating Callback.register_exception n exn, where n is an arbitrary name and
exn is an exception value of the exception to register. For example:
<<
exception Error of string
let _ = Callback.register_exception "test exception" (Error "any string")
>>
The C code can then recover the exception identifier using caml_named_value
and pass it as first argument to the functions raise_constant, raise_with_arg,
and raise_with_string (described in section 17.4.5) to actually raise the
exception. For example, here is a C function that raises the Error exception
with the given argument:
<<
void raise_error(char * msg)
{
raise_with_string(*caml_named_value("test exception"), msg);
}
>>
17.7.4 Main program in C
==========================
In normal operation, a mixed Caml/C program starts by executing the Caml
initialization code, which then may proceed to call C functions. We say that
the main program is the Caml code. In some applications, it is desirable that
the C code plays the role of the main program, calling Caml functions when
needed. This can be achieved as follows:
- The C part of the program must provide a main function, which will override
the default main function provided by the Caml runtime system. Execution
will start in the user-defined main function just like for a regular C
program.
- At some point, the C code must call caml_main(argv) to initialize the Caml
code. The argv argument is a C array of strings (type char **) which
represents the command-line arguments, as passed as second argument to main.
The Caml array Sys.argv will be initialized from this parameter. For the
bytecode compiler, argv[0] and argv[1] are also consulted to find the file
containing the bytecode.
- The call to caml_main initializes the Caml runtime system, loads the
bytecode (in the case of the bytecode compiler), and executes the
initialization code of the Caml program. Typically, this initialization code
registers callback functions using Callback.register. Once the Caml
initialization code is complete, control returns to the C code that called
caml_main.
- The C code can then invoke Caml functions using the callback mechanism (see
section 17.7.1).
17.7.5 Embedding the Caml code in the C code
==============================================
The bytecode compiler in custom runtime mode (ocamlc -custom) normally
appends the bytecode to the executable file containing the custom runtime. This
has two consequences. First, the final linking step must be performed by
ocamlc. Second, the Caml runtime library must be able to find the name of the
executable file from the command-line arguments. When using caml_main(argv) as
in section 17.7.4, this means that argv[0] or argv[1] must contain the
executable file name.
An alternative is to embed the bytecode in the C code. The -output-obj option
to ocamlc is provided for this purpose. It causes the ocamlc compiler to output
a C object file (.o file) containing the bytecode for the Caml part of the
program, as well as a caml_startup function. The C object file produced by
ocamlc -output-obj can then be linked with C code using the standard C
compiler, or stored in a C library.
The caml_startup function must be called from the main C program in order to
initialize the Caml runtime and execute the Caml initialization code. Just like
caml_main, it takes one argv parameter containing the command-line parameters.
Unlike caml_main, this argv parameter is used only to initialize Sys.argv, but
not for finding the name of the executable file.
The native-code compiler ocamlopt also supports the -output-obj option,
causing it to output a C object file containing the native code for all Caml
modules on the command-line, as well as the Caml startup code. Initialization
is performed by calling caml_startup as in the case of the bytecode compiler.
For the final linking phase, in addition to the object file produced by
-output-obj, you will have to provide the Objective Caml runtime library
(libcamlrun.a for bytecode, libasmrun.a for native-code), as well as all C
libraries that are required by the Caml libraries used. For instance, assume
the Caml part of your program uses the Unix library. With ocamlc, you should
do:
<<
ocamlc -output-obj -o camlcode.o unix.cma other .cmo and .cma files
cc -o myprog C objects and libraries \
camlcode.o -L/usr/local/lib/ocaml -lunix -lcamlrun
>>
With ocamlopt, you should do:
<<
ocamlopt -output-obj -o camlcode.o unix.cmxa other .cmx and .cmxa
files
cc -o myprog C objects and libraries \
camlcode.o -L/usr/local/lib/ocaml -lunix -lasmrun
>>
Warning:
On some ports, special options are required on the final linking phase that
links together the object file produced by the -output-obj option and the
remainder of the program. Those options are shown in the configuration file
config/Makefile generated during compilation of Objective Caml, as the
variables BYTECCLINKOPTS (for object files produced by ocamlc -output-obj) and
NATIVECCLINKOPTS (for object files produced by ocamlopt -output-obj).
Currently, the only ports that require special attention are:
- Alpha under Digital Unix / Tru64 Unix with gcc: object files produced by
ocamlc -output-obj must be linked with the gcc options -Wl,-T,12000000
-Wl,-D,14000000. This is not necessary for object files produced by ocamlopt
-output-obj.
- Windows NT: the object file produced by Objective Caml have been compiled
with the /MT flag, and therefore all other object files linked with it
should also be compiled with /MT.
17.8 Advanced example with callbacks
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This section illustrates the callback facilities described in section 17.7.
We are going to package some Caml functions in such a way that they can be
linked with C code and called from C just like any C functions. The Caml
functions are defined in the following mod.ml Caml source:
<<
(* File mod.ml -- some ``useful'' Caml functions *)
let rec fib n = if n < 2 then 1 else fib(n-1) + fib(n-2)
let format_result n = Printf.sprintf "Result is: %d\n" n
(* Export those two functions to C *)
let _ = Callback.register "fib" fib
let _ = Callback.register "format_result" format_result
>>
Here is the C stub code for calling these functions from C:
<<
/* File modwrap.c -- wrappers around the Caml functions */
#include <stdio.h>
#include <string.h>
#include <caml/mlvalues.h>
#include <caml/callback.h>
int fib(int n)
{
static value * fib_closure = NULL;
if (fib_closure == NULL) fib_closure = caml_named_value("fib");
return Int_val(callback(*fib_closure, Val_int(n)));
}
char * format_result(int n)
{
static value * format_result_closure = NULL;
if (format_result_closure == NULL)
format_result_closure = caml_named_value("format_result");
return strdup(String_val(callback(*format_result_closure, Val_int(n))));
/* We copy the C string returned by String_val to the C heap
so that it remains valid after garbage collection. */
}
>>
We now compile the Caml code to a C object file and put it in a C library
along with the stub code in modwrap.c and the Caml runtime system:
<<
ocamlc -custom -output-obj -o modcaml.o mod.ml
ocamlc -c modwrap.c
cp /usr/local/lib/ocaml/libcamlrun.a mod.a
ar r mod.a modcaml.o modwrap.o
>>
(One can also use ocamlopt -output-obj instead of ocamlc -custom -output-obj.
In this case, replace libcamlrun.a (the bytecode runtime library) by
libasmrun.a (the native-code runtime library).)
Now, we can use the two fonctions fib and format_result in any C program,
just like regular C functions. Just remember to call caml_startup once before.
<<
/* File main.c -- a sample client for the Caml functions */
#include <stdio.h>
int main(int argc, char ** argv)
{
int result;
/* Initialize Caml code */
caml_startup(argv);
/* Do some computation */
result = fib(10);
printf("fib(10) = %s\n", format_result(result));
return 0;
}
>>
To build the whole program, just invoke the C compiler as follows:
<<
cc -o prog main.c mod.a -lcurses
>>
(On some machines, you may need to put -ltermcap or -lcurses -ltermcap
instead of -lcurses.)
17.9 Advanced topic: custom blocks
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Blocks with tag Custom_tag contain both arbitrary user data and a pointer to
a C struct, with type struct custom_operations, that associates user-provided
finalization, comparison, hashing, serialization and deserialization functions
to this block.
17.9.1 The struct custom_operations
=====================================
The struct custom_operations is defined in <caml/custom.h> and contains the
following fields:
- char *identifier
A zero-terminated character string serving as an identifier for serialization
and deserialization operations.
- void (*finalize)(value v)
The finalize field contains a pointer to a C function that is called when the
block becomes unreachable and is about to be reclaimed. The block is passed
as first argument to the function. The finalize field can also be NULL to
indicate that no finalization function is associated with the block.
- int (*compare)(value v1, value v2)
The compare field contains a pointer to a C function that is called whenever
two custom blocks are compared using Caml's generic comparison operators (=,
<>, <=, >=, <, > and compare). The C function should return 0 if the data
contained in the two blocks are structurally equal, a negative integer if
the data from the first block is less than the data from the second block,
and a positive integer if the data from the first block is greater than the
data from the second block.
The compare field can be set to custom_compare_default; this default
comparison function simply raises Failure.
- long (*hash)(value v)
The hash field contains a pointer to a C function that is called whenever
Caml's generic hash operator (see module Hashtbl) is applied to a custom
block. The C function can return an arbitrary long integer representing the
hash value of the data contained in the given custom block. The hash value
must be compatible with the compare function, in the sense that two
structurally equal data (that is, two custom blocks for which compare
returns 0) must have the same hash value.
The hash field can be set to custom_hash_default, in which case the custom
block is ignored during hash computation.
- void (*serialize)(value v, unsigned long * wsize_32, unsigned long *
wsize_64)
The serialize field contains a pointer to a C function that is called whenever
the custom block needs to be serialized (marshaled) using the Caml functions
output_value or Marshal.to_.... For a custom block, those functions first
write the identifier of the block (as given by the identifier field) to the
output stream, then call the user-provided serialize function. That function
is responsible for writing the data contained in the custom block, using the
serialize_... functions defined in <caml/intext.h> and listed below. The
user-provided serialize function must then store in its wsize_32 and
wsize_64 parameters the sizes in bytes of the data part of the custom block
on a 32-bit architecture and on a 64-bit architecture, respectively.
The serialize field can be set to custom_serialize_default, in which case the
Failure exception is raised when attempting to serialize the custom block.
- unsigned long (*deserialize)(void * dst)
The deserialize field contains a pointer to a C function that is called
whenever a custom block with identifier identifier needs to be deserialized
(un-marshaled) using the Caml functions input_value or Marshal.from_....
This user-provided function is responsible for reading back the data written
by the serialize operation, using the deserialize_... functions defined in
<caml/intext.h> and listed below. It must then rebuild the data part of the
custom block and store it at the pointer given as the dst argument. Finally,
it returns the size in bytes of the data part of the custom block. This size
must be identical to the wsize_32 result of the serialize operation if the
architecture is 32 bits, or wsize_64 if the architecture is 64 bits.
The deserialize field can be set to custom_deserialize_default to indicate
that deserialization is not supported. In this case, do not register the
struct custom_operations with the deserializer using
register_custom_operations (see below).
17.9.2 Allocating custom blocks
=================================
Custom blocks must be allocated via the alloc_custom function.
alloc_custom(ops, size, used, max) returns a fresh custom block, with room for
size bytes of user data, and whose associated operations are given by ops (a
pointer to a struct custom_operations, usually statically allocated as a C
global variable).
The two parameters used and max are used to control the speed of garbage
collection when the finalized object contains pointers to out-of-heap
resources. Generally speaking, the Caml incremental major collector adjusts its
speed relative to the allocation rate of the program. The faster the program
allocates, the harder the GC works in order to reclaim quickly unreachable
blocks and avoid having large amount of ``floating garbage'' (unreferenced
objects that the GC has not yet collected).
Normally, the allocation rate is measured by counting the in-heap size of
allocated blocks. However, it often happens that finalized objects contain
pointers to out-of-heap memory blocks and other resources (such as file
descriptors, X Windows bitmaps, etc.). For those blocks, the in-heap size of
blocks is not a good measure of the quantity of resources allocated by the
program.
The two arguments used and max give the GC an idea of how much out-of-heap
resources are consumed by the finalized block being allocated: you give the
amount of resources allocated to this object as parameter used, and the maximum
amount that you want to see in floating garbage as parameter max. The units are
arbitrary: the GC cares only about the ratio used / max.
For instance, if you are allocating a finalized block holding an X Windows
bitmap of w by h pixels, and you'd rather not have more than 1 mega-pixels of
unreclaimed bitmaps, specify used = w * h and max = 1000000.
Another way to describe the effect of the used and max parameters is in terms
of full GC cycles. If you allocate many custom blocks with used / max = 1 / N,
the GC will then do one full cycle (examining every object in the heap and
calling finalization functions on those that are unreachable) every N
allocations. For instance, if used = 1 and max = 1000, the GC will do one full
cycle at least every 1000 allocations of custom blocks.
If your finalized blocks contain no pointers to out-of-heap resources, or if
the previous discussion made little sense to you, just take used = 0 and max =
1. But if you later find that the finalization functions are not called ``often
enough'', consider increasing the used / max ratio.
17.9.3 Accessing custom blocks
================================
The data part of a custom block v can be accessed via the pointer
Data_custom_val(v). This pointer has type void * and should be cast to the
actual type of the data stored in the custom block.
The contents of custom blocks are not scanned by the garbage collector, and
must therefore not contain any pointer inside the Caml heap. In other terms,
never store a Caml value in a custom block, and do not use Field, Store_field
nor modify to access the data part of a custom block. Conversely, any C data
structure (not containing heap pointers) can be stored in a custom block.
17.9.4 Writing custom serialization and deserialization functions
===================================================================
The following functions, defined in <caml/intext.h>, are provided to write
and read back the contents of custom blocks in a portable way. Those functions
handle endianness conversions when e.g. data is written on a little-endian
machine and read back on a big-endian machine.
--------------------------------------------------
| Function | Action |
--------------------------------------------------
|serialize_int_1 |Write a 1-byte integer
|serialize_int_2 |Write a 2-byte integer
|serialize_int_4 |Write a 4-byte integer
|serialize_int_8 |Write a 8-byte integer
|serialize_float_4 |Write a 4-byte float
|serialize_float_8 |Write a 8-byte float
|serialize_block_1 |Write an array of 1-byte
| |quantities
|serialize_block_2 |Write an array of 2-byte
| |quantities
|serialize_block_4 |Write an array of 4-byte
| |quantities
|serialize_block_8 |Write an array of 8-byte
| |quantities
|deserialize_uint_1 |Read an unsigned 1-byte
| |integer
|deserialize_sint_1 |Read a signed 1-byte integer
| |
|deserialize_uint_2 |Read an unsigned 2-byte
| |integer
|deserialize_sint_2 |Read a signed 2-byte integer
| |
|deserialize_uint_4 |Read an unsigned 4-byte
| |integer
|deserialize_sint_4 |Read a signed 4-byte integer
| |
|deserialize_uint_8 |Read an unsigned 8-byte
| |integer
|deserialize_sint_8 |Read a signed 8-byte integer
| |
|deserialize_float_4|Read a 4-byte float
|deserialize_float_8|Read an 8-byte float
|deserialize_block_1|Read an array of 1-byte
| |quantities
|deserialize_block_2|Read an array of 2-byte
| |quantities
|deserialize_block_4|Read an array of 4-byte
| |quantities
|deserialize_block_8|Read an array of 8-byte
| |quantities
|deserialize_error |Signal an error during
| |deserialization; input_value
| |or Marshal.from_... raise a
| |Failure exception after
| |cleaning up their internal
| |data structures
--------------------------------------------------
Serialization functions are attached to the custom blocks to which they
apply. Obviously, deserialization functions cannot be attached this way, since
the custom block does not exist yet when deserialization begins! Thus, the
struct custom_operations that contain deserialization functions must be
registered with the deserializer in advance, using the
register_custom_operations function declared in <caml/custom.h>.
Deserialization proceeds by reading the identifier off the input stream,
allocating a custom block of the size specified in the input stream, searching
the registered struct custom_operation blocks for one with the same identifier,
and calling its deserialize function to fill the data part of the custom block.
17.9.5 Choosing identifiers
=============================
Identifiers in struct custom_operations must be chosen carefully, since they
must identify uniquely the data structure for serialization and deserialization
operations. In particular, consider including a version number in the
identifier; this way, the format of the data can be changed later, yet
backward-compatible deserialisation functions can be provided.
Identifiers starting with _ (an underscore character) are reserved for the
Objective Caml runtime system; do not use them for your custom data. We
recommend to use a URL (http://mymachine.mydomain.com/mylibrary/version-number)
or a Java-style package name (com.mydomain.mymachine.mylibrary.version-number)
as identifiers, to minimize the risk of identifier collision.
17.9.6 Finalized blocks
=========================
Custom blocks generalize the finalized blocks that were present in Objective
Caml prior to version 3.00. For backward compatibility, the format of custom
blocks is compatible with that of finalized blocks, and the alloc_final
function is still available to allocate a custom block with a given
finalization function, but default comparison, hashing and serialization
functions. alloc_final(n, f, used, max) returns a fresh custom block of size n
words, with finalization function f. The first word is reserved for storing the
custom operations; the other n-1 words are available for your data. The two
parameters used and max are used to control the speed of garbage collection, as
described for alloc_custom.
Part: IV
********
The Objective Caml library
***************************
Chapter 18 The core library
*******************************
This chapter describes the functions provided by the Objective Caml core
library module: module Pervasives. This module is special in two ways:
- It is automatically linked with the user's object code files by the ocamlc
command (chapter 8).
- It is automatically ``opened'' when a compilation starts, or when the
toplevel system is launched. Hence, it is possible to use unqualified
identifiers to refer to the functions provided by the Pervasives module,
without adding a open Pervasives directive.
Conventions
*=*=*=*=*=*
The declarations from the signature of the Pervasives module are printed one
by one in typewriter font, followed by a short comment. All modules and the
identifiers they export are indexed at the end of this report.
18.1 Module Pervasives: the initially opened module
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module provides the built-in types (numbers, booleans,
strings, exceptions, references, lists, arrays, input-output
channels, ...) and the basic operations over these types.
This module is automatically opened at the beginning of each
compilation. All components of this module can therefore be
referred by their short name, without prefixing them by
`Pervasives'.
Predefined types
=================
<<
type int
>>
The type of integer numbers.
<<
type char
>>
The type of characters.
<<
type string
>>
The type of character strings.
<<
type float
>>
The type of floating-point numbers.
<<
type bool
>>
The type of booleans (truth values).
<<
type unit = ()
>>
The type of the unit value.
<<
type exn
>>
The type of exception values.
<<
type 'a array
>>
The type of arrays whose elements have type `'a'.
<<
type 'a list = [] | :: of 'a * 'a list
>>
The type of lists whose elements have type `'a'.
<<
type 'a option = None | Some of 'a
>>
The type of optional values.
<<
type ('a, 'b, 'c) format
>>
The type of format strings. `'a' is the type of the parameters
of the format, `'c' is the result type for the `printf'-style
function, and `'b' is the type of the first argument given to
`%a' and `%t' printing functions (see module `Printf').
Exceptions
===========
<<
val raise : exn -> 'a
>>
Raise the given exception value
<<
exception Match_failure of (string * int * int)
>>
Exception raised when none of the cases of a pattern-matching
apply. The arguments are the location of the pattern-matching in
the source code (file name, position of first character,
position of last character).
<<
exception Assert_failure of (string * int * int)
>>
Exception raised when an assertion fails. The arguments are the
location of the pattern-matching in the source code (file name,
position of first character, position of last character).
<<
exception Invalid_argument of string
>>
Exception raised by library functions to signal that the given
arguments do not make sense.
<<
exception Failure of string
>>
Exception raised by library functions to signal that they are
undefined on the given arguments.
<<
exception Not_found
>>
Exception raised by search functions when the desired object
could not be found.
<<
exception Out_of_memory
>>
Exception raised by the garbage collector when there is
insufficient memory to complete the computation.
<<
exception Stack_overflow
>>
Exception raised by the bytecode interpreter when the
evaluation stack reaches its maximal size. This often indicates
infinite or excessively deep recursion in the user's program.
<<
exception Sys_error of string
>>
Exception raised by the input/output functions to report an
operating system error.
<<
exception End_of_file
>>
Exception raised by input functions to signal that the end of
file has been reached.
<<
exception Division_by_zero
>>
Exception raised by division and remainder operations when
their second argument is null.
<<
exception Exit
>>
This exception is not raised by any library function. It is
provided for use in your programs.
<<
exception Sys_blocked_io
>>
A special case of `Sys_error' raised when no I/O is possible on
a non-blocking I/O channel.
<<
val invalid_arg: string -> 'a
>>
Raise exception `Invalid_argument' with the given string.
<<
val failwith: string -> 'a
>>
Raise exception `Failure' with the given string.
Comparisons
============
<<
val (=) : 'a -> 'a -> bool
>>
`e1 = e2' tests for structural equality of `e1' and `e2'.
Mutable structures (e.g. references and arrays) are equal if and
only if their current contents are structurally equal, even if
the two mutable objects are not the same physical object.
Equality between functional values raises `Invalid_argument'.
Equality between cyclic data structures may not terminate.
<<
val (<>) : 'a -> 'a -> bool
>>
Negation of `(=)'.
<<
val (<) : 'a -> 'a -> bool
val (>) : 'a -> 'a -> bool
val (<=) : 'a -> 'a -> bool
val (>=) : 'a -> 'a -> bool
>>
Structural ordering functions. These functions coincide with
the usual orderings over integers, characters, strings and
floating-point numbers, and extend them to a total ordering over
all types. The ordering is compatible with `(=)'. As in the case
of `(=)', mutable structures are compared by contents.
Comparison between functional values raises `Invalid_argument'.
Comparison between cyclic structures may not terminate.
<<
val compare: 'a -> 'a -> int
>>
`compare x y' returns `0' if `x=y', a negative integer if
`x<y', and a positive integer if `x>y'. The same restrictions as
for `=' apply. `compare' can be used as the comparison function
required by the `Set' and `Map' modules.
<<
val min: 'a -> 'a -> 'a
>>
Return the smaller of the two arguments.
<<
val max: 'a -> 'a -> 'a
>>
Return the greater of the two arguments.
<<
val (==) : 'a -> 'a -> bool
>>
`e1 == e2' tests for physical equality of `e1' and `e2'. On
integers and characters, it is the same as structural equality.
On mutable structures, `e1 == e2' is true if and only if
physical modification of `e1' also affects `e2'. On non-mutable
structures, the behavior of `(==)' is implementation-dependent,
except that `e1 == e2' implies `e1 = e2'.
<<
val (!=) : 'a -> 'a -> bool
>>
Negation of `(==)'.
Boolean operations
===================
<<
val not : bool -> bool
>>
The boolean negation.
<<
val (&&) : bool -> bool -> bool
val (&) : bool -> bool -> bool
>>
The boolean ``and''. Evaluation is sequential, left-to-right:
in `e1 && e2', `e1' is evaluated first, and if it returns
`false', `e2' is not evaluated at all.
<<
val (||) : bool -> bool -> bool
val (or) : bool -> bool -> bool
>>
The boolean ``or''. Evaluation is sequential, left-to-right: in
`e1 || e2', `e1' is evaluated first, and if it returns `true',
`e2' is not evaluated at all.
Integer arithmetic
===================
Integers are 31 bits wide (or 63 bits on 64-bit processors).
All operations are taken modulo 2^31 (or 2^63). They do not fail
on overflow.
<<
val (~-) : int -> int
>>
Unary negation. You can also write `-e' instead of `~-e'.
<<
val succ : int -> int
>>
`succ x' is `x+1'.
<<
val pred : int -> int
>>
`pred x' is `x-1'.
<<
val (+) : int -> int -> int
>>
Integer addition.
<<
val (-) : int -> int -> int
>>
Integer subtraction.
<<
val (*) : int -> int -> int
>>
Integer multiplication.
<<
val (/) : int -> int -> int
>>
Integer division. Raise `Division_by_zero' if the second
argument is 0.
<<
val (mod) : int -> int -> int
>>
Integer remainder. If `x >= 0' and `y > 0', the result of `x
mod y' satisfies the following properties: `0 <= x mod y < y'
and `x = (x / y) * y + x mod y'. If `y = 0', `x mod y' raises
`Division_by_zero'. If `x < 0' or `y < 0', the result of `x mod
y' is not specified and depends on the platform.
<<
val abs : int -> int
>>
Return the absolute value of the argument.
<<
val max_int: int
val min_int: int
>>
The greatest and smallest representable integers.
Bitwise operations
-------------------
<<
val (land) : int -> int -> int
>>
Bitwise logical and.
<<
val (lor) : int -> int -> int
>>
Bitwise logical or.
<<
val (lxor) : int -> int -> int
>>
Bitwise logical exclusive or.
<<
val lnot: int -> int
>>
Bitwise logical negation.
<<
val (lsl) : int -> int -> int
>>
`n lsl m' shifts `n' to the left by `m' bits. The result is
unspecified if `m < 0' or `m >= bitsize', where `bitsize' is
`32' on a 32-bit platform and `64' on a 64-bit platform.
<<
val (lsr) : int -> int -> int
>>
`n lsr m' shifts `n' to the right by `m' bits. This is a
logical shift: zeroes are inserted regardless of the sign of
`n'. The result is unspecified if `m < 0' or `m >= bitsize'.
<<
val (asr) : int -> int -> int
>>
`n asr m' shifts `n' to the right by `m' bits. This is an
arithmetic shift: the sign bit of `n' is replicated. The result
is unspecified if `m < 0' or `m >= bitsize'.
Floating-point arithmetic
==========================
Caml's floating-point numbers follow the IEEE 754 standard,
using double precision (64 bits) numbers. Floating-point
operations never raise an exception on overflow, underflow,
division by zero, etc. Instead, special IEEE numbers are
returned as appropriate, such as `infinity' for `1.0 /. 0.0',
`neg_infinity' for `-1.0 /. 0.0', and `nan' (``not a number'')
for `0.0 /. 0.0'. These special numbers then propagate through
floating-point computations as expected: for instance, `1.0 /.
infinity' is `0.0', and any operation with `nan' as argument
returns `nan' as result.
<<
val (~-.) : float -> float
>>
Unary negation. You can also write `-.e' instead of `~-.e'.
<<
val (+.) : float -> float -> float
>>
Floating-point addition
<<
val (-.) : float -> float -> float
>>
Floating-point subtraction
<<
val (*.) : float -> float -> float
>>
Floating-point multiplication
<<
val (/.) : float -> float -> float
>>
Floating-point division.
<<
val (**) : float -> float -> float
>>
Exponentiation
<<
val sqrt : float -> float
>>
Square root
<<
val exp : float -> float
val log : float -> float
val log10 : float -> float
>>
Exponential, natural logarithm, base 10 logarithm.
<<
val cos : float -> float
val sin : float -> float
val tan : float -> float
val acos : float -> float
val asin : float -> float
val atan : float -> float
val atan2 : float -> float -> float
>>
The usual trigonometric functions
<<
val cosh : float -> float
val sinh : float -> float
val tanh : float -> float
>>
The usual hyperbolic trigonometric functions
<<
val ceil : float -> float
val floor : float -> float
>>
Round the given float to an integer value. `floor f' returns
the greatest integer value less than or equal to `f'. `ceil f'
returns the least integer value greater than or equal to `f'.
<<
val abs_float : float -> float
>>
Return the absolute value of the argument.
<<
val mod_float : float -> float -> float
>>
`mod_float a b' returns the remainder of `a' with respect to
`b'. The returned value is `a -. n *. b', where `n' is the
quotient `a /. b' rounded towards zero to an integer.
<<
val frexp : float -> float * int
>>
`frexp f' returns the pair of the significant and the exponent
of `f'. When `f' is zero, the significant `x' and the exponent
`n' of `f' are equal to zero. When `f' is non-zero, they are
defined by `f = x *. 2 ** n' and `0.5 <= x < 1.0'.
<<
val ldexp : float -> int -> float
>>
`ldexp x n' returns `x *. 2 ** n'.
<<
val modf : float -> float * float
>>
`modf f' returns the pair of the fractional and integral part
of `f'.
<<
val float : int -> float
val float_of_int : int -> float
>>
Convert an integer to floating-point.
<<
val truncate : float -> int
val int_of_float : float -> int
>>
Truncate the given floating-point number to an integer. The
result is unspecified if it falls outside the range of
representable integers.
<<
val infinity: float
>>
Positive infinity.
<<
val neg_infinity: float
>>
Negative infinity.
<<
val nan: float
>>
A special floating-point value denoting the result of an
undefined operation such as `0.0 /. 0.0'. Stands for ``not a
number''.
<<
type fpclass =
FP_normal (* Normal number, none of the below *)
| FP_subnormal (* Number very close to 0.0, has reduced precision *)
| FP_zero (* Number is 0.0 or -0.0 *)
| FP_infinite (* Number is positive or negative infinity *)
| FP_nan (* Not a number: result of an undefined operation *)
>>
The five classes of floating-point numbers, as determined by
the `classify_float' function.
<<
val classify_float: float -> fpclass
>>
Return the class of the given floating-point number: normal,
subnormal, zero, infinite, or not a number.
String operations
==================
More string operations are provided in module `String'.
<<
val (^) : string -> string -> string
>>
String concatenation.
Character operations
=====================
More character operations are provided in module `Char'.
<<
val int_of_char : char -> int
>>
Return the ASCII code of the argument.
<<
val char_of_int : int -> char
>>
Return the character with the given ASCII code. Raise
`Invalid_argument "char_of_int"' if the argument is outside the
range 0--255.
Unit operations
================
<<
val ignore : 'a -> unit
>>
Discard the value of its argument and return `()'. For
instance, `ignore(f x)' discards the result of the
side-effecting function `f'. It is equivalent to `f x; ()',
except that the latter may generate a compiler warning; writing
`ignore(f x)' instead avoids the warning.
String conversion functions
============================
<<
val string_of_bool : bool -> string
>>
Return the string representation of a boolean.
<<
val bool_of_string : string -> bool
>>
Convert the given string to a boolean. Raise `Invalid_argument
"bool_of_string"' if the string is not `"true"' or `"false"'.
<<
val string_of_int : int -> string
>>
Return the string representation of an integer, in decimal.
<<
val int_of_string : string -> int
>>
Convert the given string to an integer. The string is read in
decimal (by default) or in hexadecimal, octal or binary if the
string begins with `0x', `0o' or `0b' respectively. Raise
`Failure "int_of_string"' if the given string is not a valid
representation of an integer.
<<
val string_of_float : float -> string
>>
Return the string representation of a floating-point number.
<<
val float_of_string : string -> float
>>
Convert the given string to a float. The result is unspecified
if the given string is not a valid representation of a float.
Pair operations
================
<<
val fst : 'a * 'b -> 'a
>>
Return the first component of a pair.
<<
val snd : 'a * 'b -> 'b
>>
Return the second component of a pair.
List operations
================
More list operations are provided in module `List'.
<<
val (@) : 'a list -> 'a list -> 'a list
>>
List concatenation.
Input/output
=============
<<
type in_channel
type out_channel
>>
The types of input channels and output channels.
<<
val stdin : in_channel
val stdout : out_channel
val stderr : out_channel
>>
The standard input, standard output, and standard error output
for the process.
Output functions on standard output
------------------------------------
<<
val print_char : char -> unit
>>
Print a character on standard output.
<<
val print_string : string -> unit
>>
Print a string on standard output.
<<
val print_int : int -> unit
>>
Print an integer, in decimal, on standard output.
<<
val print_float : float -> unit
>>
Print a floating-point number, in decimal, on standard output.
<<
val print_endline : string -> unit
>>
Print a string, followed by a newline character, on standard
output.
<<
val print_newline : unit -> unit
>>
Print a newline character on standard output, and flush
standard output. This can be used to simulate line buffering of
standard output.
Output functions on standard error
-----------------------------------
<<
val prerr_char : char -> unit
>>
Print a character on standard error.
<<
val prerr_string : string -> unit
>>
Print a string on standard error.
<<
val prerr_int : int -> unit
>>
Print an integer, in decimal, on standard error.
<<
val prerr_float : float -> unit
>>
Print a floating-point number, in decimal, on standard error.
<<
val prerr_endline : string -> unit
>>
Print a string, followed by a newline character on standard
error and flush standard error.
<<
val prerr_newline : unit -> unit
>>
Print a newline character on standard error, and flush standard
error.
Input functions on standard input
----------------------------------
<<
val read_line : unit -> string
>>
Flush standard output, then read characters from standard input
until a newline character is encountered. Return the string of
all characters read, without the newline character at the end.
<<
val read_int : unit -> int
>>
Flush standard output, then read one line from standard input
and convert it to an integer. Raise `Failure "int_of_string"' if
the line read is not a valid representation of an integer.
<<
val read_float : unit -> float
>>
Flush standard output, then read one line from standard input
and convert it to a floating-point number. The result is
unspecified if the line read is not a valid representation of a
floating-point number.
General output functions
-------------------------
<<
type open_flag =
Open_rdonly | Open_wronly | Open_append
| Open_creat | Open_trunc | Open_excl
| Open_binary | Open_text | Open_nonblock
>>
Opening modes for `open_out_gen' and `open_in_gen'.
`Open_rdonly': open for reading.
`Open_wronly': open for writing.
`Open_append': open for appending.
`Open_creat': create the file if it does not exist.
`Open_trunc': empty the file if it already exists.
`Open_excl': fail if the file already exists.
`Open_binary': open in binary mode (no conversion).
`Open_text': open in text mode (may perform conversions).
`Open_nonblock': open in non-blocking mode.
<<
val open_out : string -> out_channel
>>
Open the named file for writing, and return a new output
channel on that file, positionned at the beginning of the file.
The file is truncated to zero length if it already exists. It is
created if it does not already exists. Raise `Sys_error' if the
file could not be opened.
<<
val open_out_bin : string -> out_channel
>>
Same as `open_out', but the file is opened in binary mode, so
that no translation takes place during writes. On operating
systems that do not distinguish between text mode and binary
mode, this function behaves like `open_out'.
<<
val open_out_gen : mode:open_flag list -> perm:int -> string -> out_channel
>>
Open the named file for writing, as above. The extra argument
`mode' specify the opening mode. The extra argument `perm'
specifies the file permissions, in case the file must be
created. `open_out' and `open_out_bin' are special cases of this
function.
<<
val flush : out_channel -> unit
>>
Flush the buffer associated with the given output channel,
performing all pending writes on that channel. Interactive
programs must be careful about flushing standard output and
standard error at the right time.
<<
val output_char : out_channel -> char -> unit
>>
Write the character on the given output channel.
<<
val output_string : out_channel -> string -> unit
>>
Write the string on the given output channel.
<<
val output : out_channel -> buf:string -> pos:int -> len:int -> unit
>>
Write `len' characters from string `buf', starting at offset
`pos', to the given output channel. Raise `Invalid_argument
"output"' if `pos' and `len' do not designate a valid substring
of `buf'.
<<
val output_byte : out_channel -> int -> unit
>>
Write one 8-bit integer (as the single character with that
code) on the given output channel. The given integer is taken
modulo 256.
<<
val output_binary_int : out_channel -> int -> unit
>>
Write one integer in binary format on the given output channel.
The only reliable way to read it back is through the
`input_binary_int' function. The format is compatible across all
machines for a given version of Objective Caml.
<<
val output_value : out_channel -> 'a -> unit
>>
Write the representation of a structured value of any type to a
channel. Circularities and sharing inside the value are detected
and preserved. The object can be read back, by the function
`input_value'. See the description of module `Marshal' for more
information. `output_value' is equivalent to
`Marshal.to_channel' with an empty list of flags.
<<
val seek_out : out_channel -> int -> unit
>>
`seek_out chan pos' sets the current writing position to `pos'
for channel `chan'. This works only for regular files. On files
of other kinds (such as terminals, pipes and sockets), the
behavior is unspecified.
<<
val pos_out : out_channel -> int
>>
Return the current writing position for the given channel.
<<
val out_channel_length : out_channel -> int
>>
Return the total length (number of characters) of the given
channel. This works only for regular files. On files of other
kinds, the result is meaningless.
<<
val close_out : out_channel -> unit
>>
Close the given channel, flushing all buffered write
operations. A `Sys_error' exception is raised if any of the
functions above is called on a closed channel.
<<
val set_binary_mode_out : out_channel -> bool -> unit
>>
`set_binary_mode_out oc true' sets the channel `oc' to binary
mode: no translations take place during output.
`set_binary_mode_out oc false' sets the channel `oc' to text
mode: depending on the operating system, some translations may
take place during output. For instance, under Windows,
end-of-lines will be translated from `\n' to `\r\n'. This
function has no effect under operating systems that do not
distinguish between text mode and binary mode.
General input functions
------------------------
<<
val open_in : string -> in_channel
>>
Open the named file for reading, and return a new input channel
on that file, positionned at the beginning of the file. Raise
`Sys_error' if the file could not be opened.
<<
val open_in_bin : string -> in_channel
>>
Same as `open_in', but the file is opened in binary mode, so
that no translation takes place during reads. On operating
systems that do not distinguish between text mode and binary
mode, this function behaves like `open_in'.
<<
val open_in_gen : mode:open_flag list -> perm:int -> string -> in_channel
>>
Open the named file for reading, as above. The extra arguments
`mode' and `perm' specify the opening mode and file permissions.
`open_in' and `open_in_bin' are special cases of this function.
<<
val input_char : in_channel -> char
>>
Read one character from the given input channel. Raise
`End_of_file' if there are no more characters to read.
<<
val input_line : in_channel -> string
>>
Read characters from the given input channel, until a newline
character is encountered. Return the string of all characters
read, without the newline character at the end. Raise
`End_of_file' if the end of the file is reached at the beginning
of line.
<<
val input : in_channel -> buf:string -> pos:int -> len:int -> int
>>
Read up to `len' characters from the given channel, storing
them in string `buf', starting at character number `pos'. It
returns the actual number of characters read, between 0 and
`len' (inclusive). A return value of 0 means that the end of
file was reached. A return value between 0 and `len' exclusive
means that not all requested `len' characters were read, either
because no more characters were available at that time, or
because the implementation found it convenient to do a partial
read; `input' must be called again to read the remaining
characters, if desired. (See also `Pervasives.really_input' for
reading exactly `len' characters.) Exception `Invalid_argument
"input"' is raised if `pos' and `len' do not designate a valid
substring of `buf'.
<<
val really_input : in_channel -> buf:string -> pos:int -> len:int -> unit
>>
Read `len' characters from the given channel, storing them in
string `buf', starting at character number `pos'. Raise
`End_of_file' if the end of file is reached before `len'
characters have been read. Raise `Invalid_argument
"really_input"' if `pos' and `len' do not designate a valid
substring of `buf'.
<<
val input_byte : in_channel -> int
>>
Same as `input_char', but return the 8-bit integer representing
the character. Raise `End_of_file' if an end of file was
reached.
<<
val input_binary_int : in_channel -> int
>>
Read an integer encoded in binary format from the given input
channel. See `output_binary_int'. Raise `End_of_file' if an end
of file was reached while reading the integer.
<<
val input_value : in_channel -> 'a
>>
Read the representation of a structured value, as produced by
`output_value', and return the corresponding value. This
function is identical to `Marshal.from_channel'; see the
description of module `Marshal' for more information, in
particular concerning the lack of type safety.
<<
val seek_in : in_channel -> int -> unit
>>
`seek_in chan pos' sets the current reading position to `pos'
for channel `chan'. This works only for regular files. On files
of other kinds, the behavior is unspecified.
<<
val pos_in : in_channel -> int
>>
Return the current reading position for the given channel.
<<
val in_channel_length : in_channel -> int
>>
Return the total length (number of characters) of the given
channel. This works only for regular files. On files of other
kinds, the result is meaningless.
<<
val close_in : in_channel -> unit
>>
Close the given channel. A `Sys_error' exception is raised if
any of the functions above is called on a closed channel.
<<
val set_binary_mode_in : in_channel -> bool -> unit
>>
`set_binary_mode_in ic true' sets the channel `ic' to binary
mode: no translations take place during input.
`set_binary_mode_out ic false' sets the channel `ic' to text
mode: depending on the operating system, some translations may
take place during input. For instance, under Windows,
end-of-lines will be translated from `\r\n' to `\n'. This
function has no effect under operating systems that do not
distinguish between text mode and binary mode.
References
===========
<<
type 'a ref = { mutable contents: 'a }
>>
The type of references (mutable indirection cells) containing a
value of type `'a'.
<<
val ref : 'a -> 'a ref
>>
Return a fresh reference containing the given value.
<<
val (!) : 'a ref -> 'a
>>
`!r' returns the current contents of reference `r'. Equivalent
to `fun r -> r.contents'.
<<
val (:=) : 'a ref -> 'a -> unit
>>
`r := a' stores the value of `a' in reference `r'. Equivalent
to `fun r v -> r.contents <- v'.
<<
val incr : int ref -> unit
>>
Increment the integer contained in the given reference.
Equivalent to `fun r -> r := succ !r'.
<<
val decr : int ref -> unit
>>
Decrement the integer contained in the given reference.
Equivalent to `fun r -> r := pred !r'.
Program termination
====================
<<
val exit : int -> 'a
>>
Flush all pending writes on `stdout' and `stderr', and
terminate the process, returning the given status code to the
operating system (usually 0 to indicate no errors, and a small
positive integer to indicate failure.) An implicit `exit 0' is
performed each time a program terminates normally (but not if it
terminates because of an uncaught exception).
<<
val at_exit: (unit -> unit) -> unit
>>
Register the given function to be called at program termination
time. The functions registered with `at_exit' will be called
when the program executes `exit'. They will not be called if
the program terminates because of an uncaught exception. The
functions are called in ``last in, first out'' order: the
function most recently added with `at_exit' is called first.
Chapter 19 The standard library
***********************************
This chapter describes the functions provided by the Caml Light standard
library. The modules from the standard library are automatically linked with
the user's object code files by the ocamlc command. Hence, these modules can be
used in standalone programs without having to add any .cmo file on the command
line for the linking phase. Similarly, in interactive use, these globals can be
used in toplevel phrases without having to load any .cmo file in memory.
Unlike the Pervasive module from the core library, the modules from the
standard library are not automatically ``opened'' when a compilation starts, or
when the toplevel system is launched. Hence it is necessary to use qualified
identifiers to refer to the functions provided by these modules, or to add open
directives.
Conventions
*=*=*=*=*=*
For easy reference, the modules are listed below in alphabetical order of
module names. For each module, the declarations from its signature are printed
one by one in typewriter font, followed by a short comment. All modules and the
identifiers they export are indexed at the end of this report.
19.1 Module Arg: parsing of command line arguments
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module provides a general mechanism for extracting options
and arguments from the command line to the program.
Syntax of command lines: A keyword is a character string
starting with a `-'. An option is a keyword alone or followed by
an argument. The types of keywords are: `Unit', `Set', `Clear',
`String', `Int', `Float', and `Rest'. `Unit', `Set' and `Clear'
keywords take no argument. `String', `Int', and `Float' keywords
take the following word on the command line as an argument. A
`Rest' keyword takes the remaining of the command line as
(string) arguments. Arguments not preceded by a keyword are
called anonymous arguments.
Examples (`cmd' is assumed to be the command name):
`cmd -flag '(a unit option)
`cmd -int 1 '(an int option with argument `1')
`cmd -string foobar '(a string option with argument `"foobar"')
`cmd -float 12.34 '(a float option with argument `12.34')
`cmd a b c '(three anonymous arguments: `"a"', `"b"',
and `"c"')
`cmd a b -- c d '(two anonymous arguments and a rest option
with
` ' two arguments)
<<
type spec =
| Unit of (unit -> unit) (* Call the function with unit argument *)
| Set of bool ref (* Set the reference to true *)
| Clear of bool ref (* Set the reference to false *)
| String of (string -> unit) (* Call the function with a string argument *)
| Int of (int -> unit) (* Call the function with an int argument *)
| Float of (float -> unit) (* Call the function with a float argument *)
| Rest of (string -> unit) (* Stop interpreting keywords and call the
function with each remaining argument *)
>>
The concrete type describing the behavior associated with a
keyword.
<<
val parse : keywords:(string * spec * string) list ->
others:(string -> unit) -> errmsg:string -> unit
>>
`Arg.parse speclist anonfun usage_msg' parses the command line.
`speclist' is a list of triples `(key, spec, doc)'. `key' is the
option keyword, it must start with a `'-'' character. `spec'
gives the option type and the function to call when this option
is found on the command line. `doc' is a one-line description of
this option. `anonfun' is called on anonymous arguments. The
functions in `spec' and `anonfun' are called in the same order
as their arguments appear on the command line.
If an error occurs, `Arg.parse' exits the program, after
printing an error message as follows:
The reason for the error: unknown option, invalid or missing
argument, etc.
`usage_msg'
The list of options, each followed by the corresponding `doc'
string.
For the user to be able to specify anonymous arguments starting
with a `-', include for example `("-", String anonfun, doc)' in
`speclist'.
By default, `parse' recognizes a unit option `-help', which will
display `usage_msg' and the list of options, and exit the
program. You can override this behaviour by specifying your own
`-help' option in `speclist'.
<<
exception Bad of string
>>
Functions in `spec' or `anonfun' can raise `Arg.Bad' with an
error message to reject invalid arguments.
<<
val usage : keywords:(string * spec * string) list -> errmsg:string -> unit
>>
`Arg.usage speclist usage_msg' prints an error message including
the list of valid options. This is the same message that
`Arg.parse' prints in case of error. `speclist' and `usage_msg'
are the same as for `Arg.parse'.
<<
val current : int ref;;
>>
Position (in `Sys.argv') of the argument being processed. You
can change this value, e.g. to force `Arg.parse' to skip some
arguments.
19.2 Module Array: array operations
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
<<
val length : 'a array -> int
>>
Return the length (number of elements) of the given array.
<<
val get: 'a array -> int -> 'a
>>
`Array.get a n' returns the element number `n' of array `a'.
The first element has number 0. The last element has number
`Array.length a - 1'. Raise `Invalid_argument "Array.get"' if
`n' is outside the range 0 to `(Array.length a - 1)'. You can
also write `a.(n)' instead of `Array.get a n'.
<<
val set: 'a array -> int -> 'a -> unit
>>
`Array.set a n x' modifies array `a' in place, replacing
element number `n' with `x'. Raise `Invalid_argument
"Array.set"' if `n' is outside the range 0 to `Array.length a -
1'. You can also write `a.(n) <- x' instead of `Array.set a n
x'.
<<
val make: int -> 'a -> 'a array
val create: int -> 'a -> 'a array
>>
`Array.make n x' returns a fresh array of length `n',
initialized with `x'. All the elements of this new array are
initially physically equal to `x' (in the sense of the `=='
predicate). Consequently, if `x' is mutable, it is shared among
all elements of the array, and modifying `x' through one of the
array entries will modify all other entries at the same time.
Raise `Invalid_argument' if `n <= 0' or `n >
Sys.max_array_length'. If the value of `x' is a floating-point
number, then the maximum size is only `Sys.max_array_length /
2'. `Array.create' is a deprecated alias for `Array.make'.
<<
val init: int -> f:(int -> 'a) -> 'a array
>>
`Array.init n f' returns a fresh array of length `n', with
element number `i' initialized to the result of `f i'. In other
terms, `Array.init n f' tabulates the results of `f' applied to
the integers `0' to `n-1'.
<<
val make_matrix: dimx:int -> dimy:int -> 'a -> 'a array array
val create_matrix: dimx:int -> dimy:int -> 'a -> 'a array array
>>
`Array.make_matrix dimx dimy e' returns a two-dimensional array
(an array of arrays) with first dimension `dimx' and second
dimension `dimy'. All the elements of this new matrix are
initially physically equal to `e'. The element (`x,y') of a
matrix `m' is accessed with the notation `m.(x).(y)'. Raise
`Invalid_argument' if `dimx' or `dimy' is less than 1 or greater
than `Sys.max_array_length'. If the value of `e' is a
floating-point number, then the maximum size is only
`Sys.max_array_length / 2'. `Array.create_matrix' is a
deprecated alias for `Array.make_matrix'.
<<
val append: 'a array -> 'a array -> 'a array
>>
`Array.append v1 v2' returns a fresh array containing the
concatenation of the arrays `v1' and `v2'.
<<
val concat: 'a array list -> 'a array
>>
Same as `Array.append', but catenates a list of arrays.
<<
val sub: 'a array -> pos:int -> len:int -> 'a array
>>
`Array.sub a start len' returns a fresh array of length `len',
containing the elements number `start' to `start + len - 1' of
array `a'. Raise `Invalid_argument "Array.sub"' if `start' and
`len' do not designate a valid subarray of `a'; that is, if
`start < 0', or `len < 0', or `start + len > Array.length a'.
<<
val copy: 'a array -> 'a array
>>
`Array.copy a' returns a copy of `a', that is, a fresh array
containing the same elements as `a'.
<<
val fill: 'a array -> pos:int -> len:int -> 'a -> unit
>>
`Array.fill a ofs len x' modifies the array `a' in place,
storing `x' in elements number `ofs' to `ofs + len - 1'. Raise
`Invalid_argument "Array.fill"' if `ofs' and `len' do not
designate a valid subarray of `a'.
<<
val blit: src:'a array -> src_pos:int ->
dst:'a array -> dst_pos:int -> len:int -> unit
>>
`Array.blit v1 o1 v2 o2 len' copies `len' elements from array
`v1', starting at element number `o1', to array `v2', starting
at element number `o2'. It works correctly even if `v1' and `v2'
are the same array, and the source and destination chunks
overlap. Raise `Invalid_argument "Array.blit"' if `o1' and `len'
do not designate a valid subarray of `v1', or if `o2' and `len'
do not designate a valid subarray of `v2'.
<<
val to_list: 'a array -> 'a list
>>
`Array.to_list a' returns the list of all the elements of `a'.
<<
val of_list: 'a list -> 'a array
>>
`Array.of_list l' returns a fresh array containing the elements
of `l'.
<<
val iter: f:('a -> unit) -> 'a array -> unit
>>
`Array.iter f a' applies function `f' in turn to all the
elements of `a'. It is equivalent to `f a.(0); f a.(1); ...; f
a.(Array.length a - 1); ()'.
<<
val map: f:('a -> 'b) -> 'a array -> 'b array
>>
`Array.map f a' applies function `f' to all the elements of
`a', and builds an array with the results returned by `f': `[| f
a.(0); f a.(1); ...; f a.(Array.length a - 1) |]'.
<<
val iteri: f:(int -> 'a -> unit) -> 'a array -> unit
val mapi: f:(int -> 'a -> 'b) -> 'a array -> 'b array
>>
Same as `Array.iter' and `Array.map' respectively, but the
function is applied to the index of the element as first
argument, and the element itself as second argument.
<<
val fold_left: f:('a -> 'b -> 'a) -> init:'a -> 'b array -> 'a
>>
`Array.fold_left f x a' computes `f (... (f (f x a.(0)) a.(1))
...) a.(n-1)', where `n' is the length of the array `a'.
<<
val fold_right: f:('b -> 'a -> 'a) -> 'b array -> init:'a -> 'a
>>
`Array.fold_right f a x' computes `f a.(0) (f a.(1) ( ... (f
a.(n-1) x) ...))', where `n' is the length of the array `a'.
Sorting
--------
<<
val sort : cmp:('a -> 'a -> int) -> 'a array -> unit;;
>>
Sort an array in increasing order according to a comparison
function. The comparison function must return 0 if its arguments
compare as equal, a positive integer if the first is greater,
and a negative integer if the first is smaller. For example, the
`compare' function is a suitable comparison function. After
calling `Array.sort', the array is sorted in place in increasing
order. `Array.sort' is guaranteed to run in constant heap space
and logarithmic stack space.
The current implementation uses Heap Sort. It runs in constant
stack space.
<<
val stable_sort : cmp:('a -> 'a -> int) -> 'a array -> unit;;
>>
Same as `Array.sort', but the sorting algorithm is stable and
not guaranteed to use a fixed amount of heap memory. The current
implementation is Merge Sort. It uses `n/2' words of heap space,
where `n' is the length of the array. It is faster than the
current implementation of `Array.sort'.
19.3 Module Buffer: extensible string buffers
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module implements string buffers that automatically expand
as necessary. It provides accumulative concatenation of strings
in quasi-linear time (instead of quadratic time when strings are
concatenated pairwise).
<<
type t
>>
The abstract type of buffers.
<<
val create : int -> t
>>
`create n' returns a fresh buffer, initially empty. The `n'
parameter is the initial size of the internal string that holds
the buffer contents. That string is automatically reallocated
when more than `n' characters are stored in the buffer, but
shrinks back to `n' characters when `reset' is called. For best
performance, `n' should be of the same order of magnitude as the
number of characters that are expected to be stored in the
buffer (for instance, 80 for a buffer that holds one output
line). Nothing bad will happen if the buffer grows beyond that
limit, however. In doubt, take `n = 16' for instance. If `n' is
not between 1 and `Sys.max_string_length', it will be clipped to
that interval.
<<
val contents : t -> string
>>
Return a copy of the current contents of the buffer. The buffer
itself is unchanged.
<<
val length : t -> int
>>
Return the number of characters currently contained in the
buffer.
<<
val clear : t -> unit
>>
Empty the buffer.
<<
val reset : t -> unit
>>
Empty the buffer and deallocate the internal string holding the
buffer contents, replacing it with the initial internal string
of length `n' that was allocated by `create n'. For long-lived
buffers that may have grown a lot, `reset' allows faster
reclaimation of the space used by the buffer.
<<
val add_char : t -> char -> unit
>>
`add_char b c' appends the character `c' at the end of the
buffer `b'.
<<
val add_string : t -> string -> unit
>>
`add_string b s' appends the string `s' at the end of the
buffer `b'.
<<
val add_substring : t -> string -> pos:int -> len:int -> unit
>>
`add_substring b s ofs len' takes `len' characters from offset
`ofs' in string `s' and appends them at the end of the buffer
`b'.
<<
val add_buffer : t -> src:t -> unit
>>
`add_buffer b1 b2' appends the current contents of buffer `b2'
at the end of buffer `b1'. `b2' is not modified.
<<
val add_channel : t -> in_channel -> len:int -> unit
>>
`add_channel b ic n' reads exactly `n' character from the input
channel `ic' and stores them at the end of buffer `b'. Raise
`End_of_file' if the channel contains fewer than `n' characters.
<<
val output_buffer : out_channel -> t -> unit
>>
`output_buffer oc b' writes the current contents of buffer `b'
on the output channel `oc'.
19.4 Module Callback: registering Caml values with the C runtime
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module allows Caml values to be registered with the C
runtime under a symbolic name, so that C code can later call
back registered Caml functions, or raise registered Caml
exceptions.
<<
val register: string -> 'a -> unit
>>
`Callback.register n v' registers the value `v' under the name
`n'. C code can later retrieve a handle to `v' by calling
`caml_named_value(n)'.
<<
val register_exception: string -> exn -> unit
>>
`Callback.register_exception n exn' registers the exception
contained in the exception value `exn' under the name `n'. C
code can later retrieve a handle to the exception by calling
`caml_named_value(n)'. The exception value thus obtained is
suitable for passign as first argument to `raise_constant' or
`raise_with_arg'.
19.5 Module Char: character operations
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
val code : char -> int
>>
Return the ASCII code of the argument.
<<
val chr: int -> char
>>
Return the character with the given ASCII code. Raise
`Invalid_argument "Char.chr"' if the argument is outside the
range 0--255.
<<
val escaped : char -> string
>>
Return a string representing the given character, with special
characters escaped following the lexical conventions of
Objective Caml.
<<
val lowercase: char -> char
val uppercase: char -> char
>>
Convert the given character to its equivalent lowercase or
uppercase character, respectively.
19.6 Module Digest: MD5 message digest
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module provides functions to compute 128-bit ``digests''
of arbitrary-length strings or files. The digests are of
cryptographic quality: it is very hard, given a digest, to forge
a string having that digest. The algorithm used is MD5.
<<
type t = string
>>
The type of digests: 16-character strings.
<<
val string: string -> t
>>
Return the digest of the given string.
<<
val substring: string -> pos:int -> len:int -> t
>>
`Digest.substring s ofs len' returns the digest of the
substring of `s' starting at character number `ofs' and
containing `len' characters.
<<
val channel: in_channel -> len:int -> t
>>
`Digest.channel ic len' reads `len' characters from channel
`ic' and returns their digest.
<<
val file: string -> t
>>
Return the digest of the file whose name is given.
<<
val output: out_channel -> t -> unit
>>
Write a digest on the given output channel.
<<
val input: in_channel -> t
>>
Read a digest from the given input channel.
19.7 Module Filename: operations on file names
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
val current_dir_name : string
>>
The conventional name for the current directory (e.g. `.' in
Unix).
<<
val parent_dir_name : string
>>
The conventional name for the parent of the current directory
(e.g. `..' in Unix).
<<
val concat : string -> string -> string
>>
`concat dir file' returns a file name that designates file
`file' in directory `dir'.
<<
val is_relative : string -> bool
>>
Return `true' if the file name is relative to the current
directory, `false' if it is absolute (i.e. in Unix, starts with
`/'.
<<
val is_implicit : string -> bool
>>
Return `true' if the file name is relative and does not start
with an explicit reference to the current directory (`./' or
`../' in Unix), `false' if it starts with an explicit reference
to the root directory or the current directory.
<<
val check_suffix : string -> string -> bool
>>
`check_suffix name suff' returns `true' if the filename `name'
ends with the suffix `suff'.
<<
val chop_suffix : string -> string -> string
>>
`chop_suffix name suff' removes the suffix `suff' from the
filename `name'. The behavior is undefined if `name' does not
end with the suffix `suff'.
<<
val chop_extension : string -> string
>>
Return the given file name without its extension. The extension
is the shortest suffix starting with a period, `.xyz' for
instance. Raise `Invalid_argument' if the given name does not
contain a period.
<<
val basename : string -> string
val dirname : string -> string
>>
Split a file name into directory name / base file name. `concat
(dirname name) (basename name)' returns a file name which is
equivalent to `name'. Moreover, after setting the current
directory to `dirname name' (with `Sys.chdir'), references to
`basename name' (which is a relative file name) designate the
same file as `name' before the call to `Sys.chdir'.
<<
val temp_file : prefix:string -> suffix:string -> string
>>
`temp_file prefix suffix' returns the name of a non-existent
temporary file in the temporary directory. The base name of the
temporary file is formed by concatenating `prefix', then a
suitably chosen integer number, then `suffix'. Under Unix, the
temporary directory is `/tmp' by default; if set, the value of
the environment variable `TMPDIR' is used instead. Under
Windows, the name of the temporary directory is the value of the
environment variable `TEMP', or `C:\temp' by default. Under
MacOS, the name of the temporary directory is given by the
environment variable `TempFolder'; if not set, temporary files
are created in the current directory.
<<
val quote : string -> string;;
>>
Return a quoted version of a file name, suitable for use as one
argument in a shell command line, escaping any shell
meta-characters.
19.8 Module Format: pretty printing
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module implements a pretty-printing facility to format
text within ``pretty-printing boxes''. The pretty-printer breaks
lines at specified break hints, and indents lines according to
the box structure.
You may consider this module as providing an extension to the
`printf' facility to provide automatic line breaking. The
addition of pretty-printing annotations to your regular `printf'
formats gives you fancy indentation and line breaks.
Pretty-printing annotations are described below in the
documentation of the function `fprintf'.
You may also use the explicit box management and printing
functions provided by this module. This style is more basic but
more verbose than the `fprintf' concise formats.
For instance, the sequence `open_box (); print_string "x =";
print_space (); print_int 1; close_box ()' that prints `x = 1'
within a pretty-printing box, can be abbreviated as `printf
"@[%s@ %i@]" "x =" 1', or even shorter `printf "@[x =@ %i@]" 1'.
Rule of thumb for casual users of this library:
use simple boxes (as obtained by `open_box 0');
use simple break hints (as obtained by `print_cut ()' that
outputs a simple break hint, or by `print_space ()' that outputs
a space indicating a break hint);
once a box is opened, display its material with basic printing
functions (e. g. `print_int' and `print_string');
when the material for a box has been printed, call `close_box
()' to close the box;
at the end of your routine, evaluate `print_newline ()' to close
all remaining boxes and flush the pretty-printer.
The behaviour of pretty-printing commands is unspecified if
there is no opened pretty-printing box. Each box opened via one
of the `open_' functions below must be closed using `close_box'
for proper formatting. Otherwise, some of the material printed
in the boxes may not be output, or may be formatted incorrectly.
In case of interactive use, the system closes all opened boxes
and flushes all pending text (as with the `print_newline'
function) after each phrase. Each phrase is therefore executed
in the initial state of the pretty-printer.
Boxes
======
<<
val open_box : int -> unit;;
>>
`open_box d' opens a new pretty-printing box with offset `d'.
This box is the general purpose pretty-printing box. Material in
this box is displayed ``horizontal or vertical'': break hints
inside the box may lead to a new line, if there is no more room
on the line to print the remainder of the box, or if a new line
may lead to a new indentation (demonstrating the indentation of
the box). When a new line is printed in the box, `d' is added to
the current indentation.
<<
val close_box : unit -> unit;;
>>
Close the most recently opened pretty-printing box.
Formatting functions
=====================
<<
val print_string : string -> unit;;
>>
`print_string str' prints `str' in the current box.
<<
val print_as : int -> string -> unit;;
>>
`print_as len str' prints `str' in the current box. The
pretty-printer formats `str' as if it were of length `len'.
<<
val print_int : int -> unit;;
>>
Print an integer in the current box.
<<
val print_float : float -> unit;;
>>
Print a floating point number in the current box.
<<
val print_char : char -> unit;;
>>
Print a character in the current box.
<<
val print_bool : bool -> unit;;
>>
Print an boolean in the current box.
Break hints
============
<<
val print_space : unit -> unit;;
>>
`print_space ()' is used to separate items (typically to print
a space between two words). It indicates that the line may be
split at this point. It either prints one space or splits the
line. It is equivalent to `print_break 1 0'.
<<
val print_cut : unit -> unit;;
>>
`print_cut ()' is used to mark a good break position. It
indicates that the line may be split at this point. It either
prints nothing or splits the line. This allows line splitting at
the current point, without printing spaces or adding
indentation. It is equivalent to `print_break 0 0'.
<<
val print_break : int -> int -> unit;;
>>
Insert a break hint in a pretty-printing box. `print_break
nspaces offset' indicates that the line may be split (a newline
character is printed) at this point, if the contents of the
current box does not fit on the current line. If the line is
split at that point, `offset' is added to the current
indentation. If the line is not split, `nspaces' spaces are
printed.
<<
val print_flush : unit -> unit;;
>>
Flush the pretty printer: all opened boxes are closed, and all
pending text is displayed.
<<
val print_newline : unit -> unit;;
>>
Equivalent to `print_flush' followed by a new line.
<<
val force_newline : unit -> unit;;
>>
Force a newline in the current box. Not the normal way of
pretty-printing, you should prefer break hints.
<<
val print_if_newline : unit -> unit;;
>>
Execute the next formatting command if the preceding line has
just been split. Otherwise, ignore the next formatting command.
Margin
=======
<<
val set_margin : int -> unit;;
>>
`set_margin d' sets the value of the right margin to `d' (in
characters): this value is used to detect line overflows that
leads to split lines. Nothing happens if `d' is smaller than 2
or bigger than 999999999.
<<
val get_margin : unit -> int;;
>>
Return the position of the right margin.
Maximum indentation limit
==========================
<<
val set_max_indent : int -> unit;;
>>
`set_max_indent d' sets the value of the maximum indentation
limit to `d' (in characters): once this limit is reached, boxes
are rejected to the left, if they do not fit on the current
line. Nothing happens if `d' is smaller than 2 or bigger than
999999999.
<<
val get_max_indent : unit -> int;;
>>
Return the value of the maximum indentation limit (in
characters).
Formatting depth: maximum number of boxes allowed before ellipsis
==================================================================
<<
val set_max_boxes : int -> unit;;
>>
`set_max_boxes max' sets the maximum number of boxes
simultaneously opened. Material inside boxes nested deeper is
printed as an ellipsis (more precisely as the text returned by
`get_ellipsis_text ()'). Nothing happens if `max' is not greater
than 1.
<<
val get_max_boxes : unit -> int;;
>>
Return the maximum number of boxes allowed before ellipsis.
<<
val over_max_boxes : unit -> bool;;
>>
Test the maximum number of boxes allowed have already been
opened.
Advanced formatting
====================
<<
val open_hbox : unit -> unit;;
>>
`open_hbox ()' opens a new pretty-printing box. This box is
``horizontal'': the line is not split in this box (new lines may
still occur inside boxes nested deeper).
<<
val open_vbox : int -> unit;;
>>
`open_vbox d' opens a new pretty-printing box with offset `d'.
This box is ``vertical'': every break hint inside this box leads
to a new line. When a new line is printed in the box, `d' is
added to the current indentation.
<<
val open_hvbox : int -> unit;;
>>
`open_hvbox d' opens a new pretty-printing box with offset `d'.
This box is ``horizontal-vertical'': it behaves as an
``horizontal'' box if it fits on a single line, otherwise it
behaves as a ``vertical'' box. When a new line is printed in the
box, `d' is added to the current indentation.
<<
val open_hovbox : int -> unit;;
>>
`open_hovbox d' opens a new pretty-printing box with offset
`d'. This box is ``horizontal or vertical'': break hints inside
this box may lead to a new line, if there is no more room on the
line to print the remainder of the box. When a new line is
printed in the box, `d' is added to the current indentation.
Tabulations
============
<<
val open_tbox : unit -> unit;;
>>
Open a tabulation box.
<<
val close_tbox : unit -> unit;;
>>
Close the most recently opened tabulation box.
<<
val print_tbreak : int -> int -> unit;;
>>
Break hint in a tabulation box. `print_tbreak spaces offset'
moves the insertion point to the next tabulation (`spaces' being
added to this position). Nothing occurs if insertion point is
already on a tabulation mark. If there is no next tabulation on
the line, then a newline is printed and the insertion point
moves to the first tabulation of the box. If a new line is
printed, `offset' is added to the current indentation.
<<
val set_tab : unit -> unit;;
>>
Set a tabulation mark at the current insertion point.
<<
val print_tab : unit -> unit;;
>>
`print_tab ()' is equivalent to `print_tbreak (0,0)'.
Ellipsis
=========
<<
val set_ellipsis_text : string -> unit;;
>>
Set the text of the ellipsis printed when too many boxes are
opened (a single dot, `.', by default).
<<
val get_ellipsis_text : unit -> string;;
>>
Return the text of the ellipsis.
Redirecting formatter output
=============================
<<
val set_formatter_out_channel : out_channel -> unit;;
>>
Redirect the pretty-printer output to the given channel.
Changing the meaning of printing material
==========================================
<<
val set_formatter_output_functions :
out:(buf:string -> pos:int -> len:int -> unit) ->
flush:(unit -> unit) -> unit;;
>>
`set_formatter_output_functions out flush' redirects the
pretty-printer output to the functions `out' and `flush'. The
`out' function performs the pretty-printer output. It is called
with a string `s', a start position `p', and a number of
characters `n'; it is supposed to output characters `p' to
`p+n-1' of `s'. The `flush' function is called whenever the
pretty-printer is flushed using `print_flush' or
`print_newline'.
<<
val get_formatter_output_functions :
unit -> (buf:string -> pos:int -> len:int -> unit) * (unit -> unit);;
>>
Return the current output functions of the pretty-printer.
** Changing the meaning of pretty printing (indentation, line
breaking, and printing material)
<<
val set_all_formatter_output_functions :
out:(buf:string -> pos:int -> len:int -> unit) ->
flush:(unit -> unit) ->
newline:(unit -> unit) -> space:(int -> unit) -> unit;;
>>
`set_all_formatter_output_functions out flush outnewline
outspace' redirects the pretty-printer output to the functions
`out' and `flush' as described in
`set_formatter_output_functions'. In addition, the
pretty-printer function that outputs a newline is set to the
function `outnewline' and the function that outputs indentation
spaces is set to the function `outspace'. This way, you can
change the meaning of indentation (which can be something else
than just printing a space character) and the meaning of new
lines opening (which can be connected to any other action needed
by the application at hand). The two functions `outspace' and
`outnewline' are normally connected to `out' and `flush':
respective default values for `outspace' and `outnewline' are
`out (String.make n ' ') 0 n' and `out "\n" 0 1'.
<<
val get_all_formatter_output_functions : unit ->
(buf:string -> pos:int -> len:int -> unit) * (unit -> unit) *
(unit -> unit) * (int -> unit);;
>>
Return the current output functions of the pretty-printer,
including line breaking and indentation functions.
Multiple formatted output
==========================
<<
type formatter;;
>>
Abstract data type corresponding to a pretty-printer and all
its machinery. Defining new pretty-printers permits the output
of material in parallel on several channels. Parameters of the
pretty-printer are local to the pretty-printer: margin, maximum
indentation limit, maximum number of boxes simultaneously
opened, ellipsis, and so on, are specific to each pretty-printer
and may be fixed independently. Given an output channel `oc', a
new formatter writing to that channel is obtained by calling
`formatter_of_out_channel oc'. Alternatively the
`make_formatter' function allocates a new formatter with
explicit output and flushing functions (convenient to output
material to strings for instance).
<<
val formatter_of_out_channel : out_channel -> formatter;;
>>
`formatter_of_out_channel oc' returns a new formatter that
writes to the corresponding channel `oc'.
<<
val std_formatter : formatter;;
>>
The standard formatter used by the formatting functions above.
It is defined as `formatter_of_out_channel stdout'.
<<
val err_formatter : formatter;;
>>
A formatter to use with formatting functions below for output
to standard error. It is defined as `formatter_of_out_channel
stderr'.
<<
val formatter_of_buffer : Buffer.t -> formatter;;
>>
`formatter_of_buffer b' returns a new formatter writing to
buffer `b'. As usual, the formatter has to be flushed at the end
of pretty printing, using `pp_print_flush' or
`pp_print_newline', to display all the pending material. In this
case the buffer is also flushed using `Buffer.flush'.
<<
val stdbuf : Buffer.t;;
>>
The string buffer in which `str_formatter' writes.
<<
val str_formatter : formatter;;
>>
A formatter to use with formatting functions below for output
to the `stdbuf' string buffer.
<<
val flush_str_formatter : unit -> string;;
>>
Returns the material printed with `str_formatter', flushes the
formatter and reset the corresponding buffer. `str_formatter' is
defined as `formatter_of_buffer stdbuf'.
<<
val make_formatter :
out:(buf:string -> pos:int -> len:int -> unit) ->
flush:(unit -> unit) -> formatter;;
>>
`make_formatter out flush' returns a new formatter that writes
according to the output function `out', and the flushing
function `flush'. Hence, a formatter to out channel `oc' is
returned by `make_formatter (output oc) (fun () -> flush oc)'.
<<
val pp_open_hbox : formatter -> unit -> unit;;
val pp_open_vbox : formatter -> int -> unit;;
val pp_open_hvbox : formatter -> int -> unit;;
val pp_open_hovbox : formatter -> int -> unit;;
val pp_open_box : formatter -> int -> unit;;
val pp_close_box : formatter -> unit -> unit;;
val pp_print_string : formatter -> string -> unit;;
val pp_print_as : formatter -> int -> string -> unit;;
val pp_print_int : formatter -> int -> unit;;
val pp_print_float : formatter -> float -> unit;;
val pp_print_char : formatter -> char -> unit;;
val pp_print_bool : formatter -> bool -> unit;;
val pp_print_break : formatter -> int -> int -> unit;;
val pp_print_cut : formatter -> unit -> unit;;
val pp_print_space : formatter -> unit -> unit;;
val pp_force_newline : formatter -> unit -> unit;;
val pp_print_flush : formatter -> unit -> unit;;
val pp_print_newline : formatter -> unit -> unit;;
val pp_print_if_newline : formatter -> unit -> unit;;
val pp_open_tbox : formatter -> unit -> unit;;
val pp_close_tbox : formatter -> unit -> unit;;
val pp_print_tbreak : formatter -> int -> int -> unit;;
val pp_set_tab : formatter -> unit -> unit;;
val pp_print_tab : formatter -> unit -> unit;;
val pp_set_margin : formatter -> int -> unit;;
val pp_get_margin : formatter -> unit -> int;;
val pp_set_max_indent : formatter -> int -> unit;;
val pp_get_max_indent : formatter -> unit -> int;;
val pp_set_max_boxes : formatter -> int -> unit;;
val pp_get_max_boxes : formatter -> unit -> int;;
val pp_over_max_boxes : formatter -> unit -> bool;;
val pp_set_ellipsis_text : formatter -> string -> unit;;
val pp_get_ellipsis_text : formatter -> unit -> string;;
val pp_set_formatter_out_channel : formatter -> out_channel -> unit;;
val pp_set_formatter_output_functions : formatter ->
out:(buf:string -> pos:int -> len:int -> unit) ->
flush:(unit -> unit) -> unit;;
val pp_get_formatter_output_functions : formatter -> unit ->
(buf:string -> pos:int -> len:int -> unit) * (unit -> unit);;
val pp_set_all_formatter_output_functions : formatter ->
out:(buf:string -> pos:int -> len:int -> unit) ->
flush:(unit -> unit) ->
newline:(unit -> unit) -> space:(int -> unit) -> unit;;
val pp_get_all_formatter_output_functions : formatter -> unit ->
(buf:string -> pos:int -> len:int -> unit) * (unit -> unit) *
(unit -> unit) * (int -> unit);;
>>
The basic functions to use with formatters. These functions are
the basic ones: usual functions operating on the standard
formatter are defined via partial evaluation of these
primitives. For instance, `print_string' is equal to
`pp_print_string std_formatter'.
<<
val fprintf : formatter -> ('a, formatter, unit) format -> 'a;;
>>
`fprintf ff format arg1 ... argN' formats the arguments `arg1'
to `argN' according to the format string `format', and outputs
the resulting string on the formatter `ff'. The format is a
character string which contains three types of objects: plain
characters and conversion specifications as specified in the
`printf' module, and pretty-printing indications. The
pretty-printing indication characters are introduced by a `@'
character, and their meanings are:
`@[': open a pretty-printing box. The type and offset of the box
may be optionally specified with the following syntax: the `<'
character, followed by an optional box type indication, then an
optional integer offset, and the closing `>' character. Box
type is one of `h', `v', `hv', `b', or `hov', which stand
respectively for an horizontal box, a vertical box, an
``horizontal-vertical'' box, or an ``horizontal or vertical''
box (`b' standing for an ``horizontal or vertical'' box
demonstrating indentation and `hov' standing for a
regular``horizontal or vertical'' box). For instance, `@[<hov
2>' opens an ``horizontal or vertical'' box with indentation 2
as obtained with `open_hovbox 2'. For more details about boxes,
see the various box opening functions `open_*box'.
`@]': close the most recently opened pretty-printing box.
`@,': output a good break as with `print_cut ()'.
`@ ': output a space, as with `print_space ()'.
`@\n': force a newline, as with `force_newline ()'.
`@;': output a good break as with `print_break'. The `nspaces'
and `offset' parameters of the break may be optionally specified
with the following syntax: the `<' character, followed by an
integer `nspaces' value, then an integer offset, and a closing
`>' character.
`@?': flush the pretty printer as with `print_flush ()'.
`@.': flush the pretty printer and output a new line, as with
`print_newline ()'.
`@<n>': print the following item as if it were of length `n'.
Hence, `printf "@<0>%s" arg' is equivalent to `print_as 0 arg'.
If `@<n>' is not followed by a conversion specification, then
the following character of the format is printed as if it were
of length `n'.
`@@': print a plain `@' character.
Example: `printf "@[%s@ %d@]" "x =" 1' is equivalent to
`open_box (); print_string "x ="; print_space (); print_int 1;
close_box ()'. It prints `x = 1' within a pretty-printing box.
<<
val bprintf: Buffer.t -> ('a, formatter, unit) format -> 'a;;
>>
Same as `fprintf', but instead of printing on a formatter,
writes into the buffer argument.
<<
val printf : ('a, formatter, unit) format -> 'a;;
>>
Same as `fprintf', but output on `std_formatter'.
<<
val eprintf: ('a, formatter, unit) format -> 'a;;
>>
Same as `fprintf', but output on `err_formatter'.
<<
val sprintf: ('a, unit, string) format -> 'a;;
>>
Same as `printf', but instead of printing on a formatter,
return a string containing the result of formatting the
arguments.
19.9 Module Gc: memory management control and statistics; finalised values
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<<
type stat = {
minor_words : float;
promoted_words : float;
major_words : float;
minor_collections : int;
major_collections : int;
heap_words : int;
heap_chunks : int;
live_words : int;
live_blocks : int;
free_words : int;
free_blocks : int;
largest_free : int;
fragments : int;
compactions : int;
}
>>
The memory management counters are returned in a `stat' record.
The fields of this record are:
`minor_words' Number of words allocated in the minor heap since
the program was started.
`promoted_words' Number of words allocated in the minor heap
that survived a minor collection and were moved to the major
heap since the program was started.
`major_words' Number of words allocated in the major heap,
including the promoted words, since the program was started.
`minor_collections' Number of minor collections since the
program was started.
`major_collections' Number of major collection cycles, not
counting the current cycle, since the program was started.
`heap_words' Total size of the major heap, in words.
`heap_chunks' Number of times the major heap size was increased
since the program was started (including the initial allocation
of the heap).
`live_words' Number of words of live data in the major heap,
including the header words.
`live_blocks' Number of live blocks in the major heap.
`free_words' Number of words in the free list.
`free_blocks' Number of blocks in the free list.
`largest_free' Size (in words) of the largest block in the free
list.
`fragments' Number of wasted words due to fragmentation. These
are 1-words free blocks placed between two live blocks. They
cannot be inserted in the free list, thus they are not available
for allocation.
`compactions' Number of heap compactions since the program was
started.
The total amount of memory allocated by the program since it was
started is (in words) `minor_words + major_words -
promoted_words'. Multiply by the word size (4 on a 32-bit
machine, 8 on a 64-bit machine) to get the number of bytes.
<<
type control = {
mutable minor_heap_size : int;
mutable major_heap_increment : int;
mutable space_overhead : int;
mutable verbose : int;
mutable max_overhead : int;
mutable stack_limit : int;
}
>>
The GC parameters are given as a `control' record. The fields
are:
`minor_heap_size' The size (in words) of the minor heap.
Changing this parameter will trigger a minor collection.
Default: 32k.
`major_heap_increment' The minimum number of words to add to the
major heap when increasing it. Default: 62k.
`space_overhead' The major GC speed is computed from this
parameter. This is the memory that will be "wasted" because the
GC does not immediatly collect unreachable blocks. It is
expressed as a percentage of the memory used for live data. The
GC will work more (use more CPU time and collect blocks more
eagerly) if `space_overhead' is smaller. The computation of the
GC speed assumes that the amount of live data is constant.
Default: 42.
`max_overhead' Heap compaction is triggered when the estimated
amount of free memory is more than `max_overhead' percent of the
amount of live data. If `max_overhead' is set to 0, heap
compaction is triggered at the end of each major GC cycle (this
setting is intended for testing purposes only). If `max_overhead
>= 1000000', compaction is never triggered. Default: 1000000.
`verbose' This value controls the GC messages on standard error
output. It is a sum of some of the following flags, to print
messages on the corresponding events:
`0x01' Start of major GC cycle.
`0x02' Minor collection and major GC slice.
`0x04' Growing and shrinking of the heap.
`0x08' Resizing of stacks and memory manager tables.
`0x10' Heap compaction.
`0x20' Change of GC parameters.
`0x40' Computation of major GC slice size.
`0x80' Calling of finalisation functions.
`0x100' Bytecode executable search at start-up. Default: 0.
`stack_limit' The maximum size of the stack (in words). This is
only relevant to the byte-code runtime, as the native code
runtime uses the operating system's stack. Default: 256k.
<<
val stat : unit -> stat
>>
Return the current values of the memory management counters in
a `stat' record.
<<
val counters : unit -> (float * float * float)
>>
Return `(minor_words, promoted_words, major_words)'. Much
faster than `stat'.
<<
val get : unit -> control
>>
Return the current values of the GC parameters in a `control'
record.
<<
val set : control -> unit
>>
`set r' changes the GC parameters according to the `control'
record `r'. The normal usage is:
`Gc.set { (Gc.get()) with Gc.verbose = 13 }'
<<
val minor : unit -> unit
>>
Trigger a minor collection.
<<
val major : unit -> unit
>>
Finish the current major collection cycle.
<<
val full_major : unit -> unit
>>
Finish the current major collection cycle and perform a
complete new cycle. This will collect all currently unreachable
blocks.
<<
val compact : unit -> unit = "gc_compaction";;
>>
Perform a full major collection and compact the heap. Note that
heap compaction is a lengthy operation.
<<
val print_stat : out_channel -> unit
>>
Print the current values of the memory management counters (in
human-readable form) into the channel argument.
<<
val allocated_bytes : unit -> float
>>
Return the total number of bytes allocated since the program
was started. It is returned as a `float' to avoid overflow
problems with `int' on 32-bit machines.
<<
val finalise : ('a -> unit) -> 'a -> unit;;
>>
`Gc.finalise f v' registers `f' as a finalisation function for
`v'. `v' must be heap-allocated. `f' will be called with `v' as
argument at some point between the first time `v' becomes
unreachable and the time `v' is collected by the GC. Several
functions can be registered for the same value, or even several
instances of the same function. Each instance will be called
once (or never, if the program terminates before the GC
deallocates `v').
A number of pitfalls are associated with finalised values:
finalisation functions are called asynchronously, sometimes even
during the execution of other finalisation functions. In a
multithreaded program, finalisation functions are called from
any thread, thus they cannot not acquire any mutex.
Anything reachable from the closure of finalisation functions is
considered reachable, so the following code will not work:
` let v = ... in Gc.finalise (fun x -> ...) v ' Instead you
should write:
` let f = fun x -> ... ;; let v = ... in Gc.finalise f v '
The `f' function can use all features of O'Caml, including
assignments that make the value reachable again (indeed, the
value is already reachable from the stack during the execution
of the function). It can also loop forever (in this case, the
other finalisation functions will be called during the execution
of f). It can call `Gc.finalise' on `v' or other values to
register other functions or even itself. It can raise an
exception; in this case the exception will interrupt whatever
the program was doing when the function was called.
`Gc.finalise' will raise `Invalid_argument' if `v' is not
heap-allocated. Some examples of values that are not
heap-allocated are integers, constant constructors, booleans,
the empty array, the empty list, the unit value. The exact list
of what is heap-allocated or not is implementation-dependent.
You should also be aware that some optimisations will duplicate
some immutable values, especially floating-point numbers when
stored into arrays, so they can be finalised and collected while
another copy is still in use by the program.
<<
type alarm;;
>>
An alarm is a piece of data that calls a user function at the
end of each major GC cycle. The following functions are provided
to create and delete alarms.
<<
val create_alarm : (unit -> unit) -> alarm;;
>>
`create_alarm f' will arrange for f to be called at the end of
each major GC cycle. A value of type `alarm' is returned that
you can use to call `delete_alarm'.
<<
val delete_alarm : alarm -> unit;;
>>
`delete_alarm a' will stop the calls to the function associated
to `a'. Calling `delete_alarm a' again has no effect.
19.10 Module Genlex: a generic lexical analyzer
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module implements a simple ``standard'' lexical analyzer,
presented as a function from character streams to token streams.
It implements roughly the lexical conventions of Caml, but is
parameterized by the set of keywords of your language.
<<
type token =
Kwd of string
| Ident of string
| Int of int
| Float of float
| String of string
| Char of char
>>
The type of tokens. The lexical classes are: `Int' and `Float'
for integer and floating-point numbers; `String' for string
literals, enclosed in double quotes; `Char' for character
literals, enclosed in single quotes; `Ident' for identifiers
(either sequences of letters, digits, underscores and quotes, or
sequences of ``operator characters'' such as `+', `*', etc); and
`Kwd' for keywords (either identifiers or single ``special
characters'' such as `(', `}', etc).
<<
val make_lexer: string list -> (char Stream.t -> token Stream.t)
>>
Construct the lexer function. The first argument is the list of
keywords. An identifier `s' is returned as `Kwd s' if `s'
belongs to this list, and as `Ident s' otherwise. A special
character `s' is returned as `Kwd s' if `s' belongs to this
list, and cause a lexical error (exception `Parse_error')
otherwise. Blanks and newlines are skipped. Comments delimited
by `(*' and `*)' are skipped as well, and can be nested.
Example: a lexer suitable for a desk calculator is obtained by
<<
let lexer = make_lexer ["+";"-";"*";"/";"let";"=";
"("; ")"]
>>
The associated parser would be a function from `token stream'
to, for instance, `int', and would have rules such as:
<<
let parse_expr = parser
[< 'Int n >] -> n
| [< 'Kwd "("; n = parse_expr; 'Kwd ")" >] ->
n
| [< n1 = parse_expr; n2 = parse_remainder n1
>] -> n2
and parse_remainder n1 = parser
[< 'Kwd "+"; n2 = parse_expr >] -> n1+n2
| ...
>>
19.11 Module Hashtbl: hash tables and hash functions
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Hash tables are hashed association tables, with in-place
modification.
Generic interface
==================
<<
type ('a, 'b) t
>>
The type of hash tables from type `'a' to type `'b'.
<<
val create : int -> ('a,'b) t
>>
`Hashtbl.create n' creates a new, empty hash table, with
initial size `n'. For best results, `n' should be on the order
of the expected number of elements that will be in the table.
The table grows as needed, so `n' is just an initial guess.
<<
val clear : ('a, 'b) t -> unit
>>
Empty a hash table.
<<
val add : ('a, 'b) t -> key:'a -> data:'b -> unit
>>
`Hashtbl.add tbl x y' adds a binding of `x' to `y' in table
`tbl'. Previous bindings for `x' are not removed, but simply
hidden. That is, after performing `Hashtbl.remove tbl x', the
previous binding for `x', if any, is restored. (Same behavior as
with association lists.)
<<
val find : ('a, 'b) t -> 'a -> 'b
>>
`Hashtbl.find tbl x' returns the current binding of `x' in
`tbl', or raises `Not_found' if no such binding exists.
<<
val find_all : ('a, 'b) t -> 'a -> 'b list
>>
`Hashtbl.find_all tbl x' returns the list of all data
associated with `x' in `tbl'. The current binding is returned
first, then the previous bindings, in reverse order of
introduction in the table.
<<
val mem : ('a, 'b) t -> 'a -> bool
>>
`Hashtbl.mem tbl x' checks if `x' is bound in `tbl'.
<<
val remove : ('a, 'b) t -> 'a -> unit
>>
`Hashtbl.remove tbl x' removes the current binding of `x' in
`tbl', restoring the previous binding if it exists. It does
nothing if `x' is not bound in `tbl'.
<<
val replace : ('a, 'b) t -> key:'a -> data:'b -> unit
>>
`Hashtbl.replace tbl x y' replaces the current binding of `x'
in `tbl' by a binding of `x' to `y'. If `x' is unbound in `tbl',
a binding of `x' to `y' is added to `tbl'. This is functionally
equivalent to `Hashtbl.remove tbl x' followed by `Hashtbl.add
tbl x y'.
<<
val iter : f:(key:'a -> data:'b -> unit) -> ('a, 'b) t -> unit
>>
`Hashtbl.iter f tbl' applies `f' to all bindings in table
`tbl'. `f' receives the key as first argument, and the
associated value as second argument. The order in which the
bindings are passed to `f' is unspecified. Each binding is
presented exactly once to `f'.
Functorial interface
=====================
<<
module type HashedType =
sig
type t
val equal: t -> t -> bool
val hash: t -> int
end
>>
The input signature of the functor `Hashtbl.Make'. `t' is the
type of keys. `equal' is the equality predicate used to compare
keys. `hash' is a hashing function on keys, returning a
non-negative integer. It must be such that if two keys are equal
according to `equal', then they must have identical hash values
as computed by `hash'. Examples: suitable (`equal', `hash')
pairs for arbitrary key types include (`(=)', `Hashtbl.hash')
for comparing objects by structure, and (`(==)', `Hashtbl.hash')
for comparing objects by addresses (e.g. for mutable or cyclic
keys).
<<
module type S =
sig
type key
type 'a t
val create: int -> 'a t
val clear: 'a t -> unit
val add: 'a t -> key:key -> data:'a -> unit
val remove: 'a t -> key -> unit
val find: 'a t -> key -> 'a
val find_all: 'a t -> key -> 'a list
val replace : 'a t -> key:key -> data:'a -> unit
val mem: 'a t -> key -> bool
val iter: f:(key:key -> data:'a -> unit) -> 'a t -> unit
end
module Make(H: HashedType): (S with type key = H.t)
>>
The functor `Hashtbl.Make' returns a structure containing a
type `key' of keys and a type `'a t' of hash tables associating
data of type `'a' to keys of type `key'. The operations perform
similarly to those of the generic interface, but use the hashing
and equality functions specified in the functor argument `H'
instead of generic equality and hashing.
The polymorphic hash primitive
===============================
<<
val hash : 'a -> int
>>
`Hashtbl.hash x' associates a positive integer to any value of
any type. It is guaranteed that if `x = y', then `hash x = hash
y'. Moreover, `hash' always terminates, even on cyclic
structures.
<<
val hash_param : int -> int -> 'a -> int
>>
`Hashtbl.hash_param n m x' computes a hash value for `x', with
the same properties as for `hash'. The two extra parameters `n'
and `m' give more precise control over hashing. Hashing performs
a depth-first, right-to-left traversal of the structure `x',
stopping after `n' meaningful nodes were encountered, or `m'
nodes, meaningful or not, were encountered. Meaningful nodes
are: integers; floating-point numbers; strings; characters;
booleans; and constant constructors. Larger values of `m' and
`n' means that more nodes are taken into account to compute the
final hash value, and therefore collisions are less likely to
happen. However, hashing takes longer. The parameters `m' and
`n' govern the tradeoff between accuracy and speed.
19.12 Module Int32: 32-bit integers
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module provides operations on the type `int32' of signed
32-bit integers. Unlike the built-in `int' type, the type
`int32' is guaranteed to be exactly 32-bit wide on all
platforms. All arithmetic operations over `int32' are taken
modulo 2^32.
Performance notice: values of type `int32' occupy more memory
space than values of type `int', and arithmetic operations on
`int32' are generally slower than those on `int'. Use `int32'
only when the application requires exact 32-bit arithmetic.
<<
val zero : int32
val one : int32
val minus_one : int32
>>
The 32-bit integers 0, 1, -1.
<<
val neg : int32 -> int32
>>
Unary negation.
<<
val add : int32 -> int32 -> int32
>>
Addition.
<<
val sub : int32 -> int32 -> int32
>>
Subtraction.
<<
val mul : int32 -> int32 -> int32
>>
Multiplication.
<<
val div : int32 -> int32 -> int32
>>
Integer division. Raise `Division_by_zero' if the second
argument is zero.
<<
val rem : int32 -> int32 -> int32
>>
Integer remainder. If `x >= 0' and `y > 0', the result of
`Int32.rem x y' satisfies the following properties: `0 <=
Int32.rem x y < y' and `x = Int32.add (Int32.mul (Int32.div x y)
y) (Int32.rem x y)'. If `y = 0', `Int32.rem x y' raises
`Division_by_zero'. If `x < 0' or `y < 0', the result of
`Int32.rem x y' is not specified and depends on the platform.
<<
val succ : int32 -> int32
>>
Successor. `Int32.succ x' is `Int32.add x Int32.one'.
<<
val pred : int32 -> int32
>>
Predecessor. `Int32.pred x' is `Int32.sub x Int32.one'.
<<
val abs : int32 -> int32
>>
Return the absolute value of its argument.
<<
val max_int : int32
>>
The greatest representable 32-bit integer, 2^31 - 1.
<<
val min_int : int32
>>
The smallest representable 32-bit integer, -2^31.
<<
val logand : int32 -> int32 -> int32
>>
Bitwise logical and.
<<
val logor : int32 -> int32 -> int32
>>
Bitwise logical or.
<<
val logxor : int32 -> int32 -> int32
>>
Bitwise logical exclusive or.
<<
val lognot : int32 -> int32
>>
Bitwise logical negation
<<
val shift_left : int32 -> int -> int32
>>
`Int32.shift_left x y' shifts `x' to the left by `y' bits. The
result is unspecified if `y < 0' or `y >= 32'.
<<
val shift_right : int32 -> int -> int32
>>
`Int32.shift_right x y' shifts `x' to the right by `y' bits.
This is an arithmetic shift: the sign bit of `x' is replicated
and inserted in the vacated bits. The result is unspecified if
`y < 0' or `y >= 32'.
<<
val shift_right_logical : int32 -> int -> int32
>>
`Int32.shift_right_logical x y' shifts `x' to the right by `y'
bits. This is a logical shift: zeroes are inserted in the
vacated bits regardless of the sign of `x'. The result is
unspecified if `y < 0' or `y >= 32'.
<<
val of_int : int -> int32
>>
Convert the given integer (type `int') to a 32-bit integer
(type `int32').
<<
val to_int : int32 -> int
>>
Convert the given 32-bit integer (type `int32') to an integer
(type `int'). On 32-bit platforms, the 32-bit integer is taken
modulo 2^31, i.e. the high-order bit is lost during the
conversion. On 64-bit platforms, the conversion is exact.
<<
val of_float : float -> int32
>>
Convert the given floating-point number to a 32-bit integer,
discarding the fractional part (truncate towards 0). The result
of the conversion is undefined if, after truncation, the number
is outside the range `Int32.min_int, Int32.max_int'.
<<
val to_float : int32 -> float
>>
Convert the given 32-bit integer to a floating-point number.
<<
val of_string : string -> int32
>>
Convert the given string to a 32-bit integer. The string is
read in decimal (by default) or in hexadecimal, octal or binary
if the string begins with `0x', `0o' or `0b' respectively. Raise
`Failure "int_of_string"' if the given string is not a valid
representation of an integer.
<<
val to_string : int32 -> string
>>
Return the string representation of its argument, in signed
decimal.
<<
val format : string -> int32 -> string
>>
`Int32.format fmt n' return the string representation of the
32-bit integer `n' in the format specified by `fmt'. `fmt' is a
`Printf'-style format containing exactly one `%d', `%i', `%u',
`%x', `%X' or `%o' conversion specification. See the
documentation of the `Printf' module for more information,
19.13 Module Int64: 64-bit integers
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module provides operations on the type `int64' of signed
64-bit integers. Unlike the built-in `int' type, the type
`int64' is guaranteed to be exactly 64-bit wide on all
platforms. All arithmetic operations over `int64' are taken
modulo 2^64.
The type `int64' is supported on all 64-bit platforms, as well
as on all 32-bit platforms for which the C compiler supports
64-bit arithmetic. On 32-bit platforms without support for
64-bit arithmetic, all functions in this module raise an
`Invalid_argument' exception.
Performance notice: values of type `int64' occupy more memory
space than values of type `int', and arithmetic operations on
`int64' are generally slower than those on `int'. Use `int64'
only when the application requires exact 64-bit arithmetic.
<<
val zero : int64
val one : int64
val minus_one : int64
>>
The 64-bit integers 0, 1, -1.
<<
val neg : int64 -> int64
>>
Unary negation.
<<
val add : int64 -> int64 -> int64
>>
Addition.
<<
val sub : int64 -> int64 -> int64
>>
Subtraction.
<<
val mul : int64 -> int64 -> int64
>>
Multiplication.
<<
val div : int64 -> int64 -> int64
>>
Integer division. Raise `Division_by_zero' if the second
argument is zero.
<<
val rem : int64 -> int64 -> int64
>>
Integer remainder. If `x >= 0' and `y > 0', the result of
`Int64.rem x y' satisfies the following properties: `0 <=
Int64.rem x y < y' and `x = Int64.add (Int64.mul (Int64.div x y)
y) (Int64.rem x y)'. If `y = 0', `Int64.rem x y' raises
`Division_by_zero'. If `x < 0' or `y < 0', the result of
`Int64.rem x y' is not specified and depends on the platform.
<<
val succ : int64 -> int64
>>
Successor. `Int64.succ x' is `Int64.add x Int64.one'.
<<
val pred : int64 -> int64
>>
Predecessor. `Int64.pred x' is `Int64.sub x Int64.one'.
<<
val abs : int64 -> int64
>>
Return the absolute value of its argument.
<<
val max_int : int64
>>
The greatest representable 64-bit integer, 2^63 - 1.
<<
val min_int : int64
>>
The smallest representable 64-bit integer, -2^63.
<<
val logand : int64 -> int64 -> int64
>>
Bitwise logical and.
<<
val logor : int64 -> int64 -> int64
>>
Bitwise logical or.
<<
val logxor : int64 -> int64 -> int64
>>
Bitwise logical exclusive or.
<<
val lognot : int64 -> int64
>>
Bitwise logical negation
<<
val shift_left : int64 -> int -> int64
>>
`Int64.shift_left x y' shifts `x' to the left by `y' bits. The
result is unspecified if `y < 0' or `y >= 64'.
<<
val shift_right : int64 -> int -> int64
>>
`Int64.shift_right x y' shifts `x' to the right by `y' bits.
This is an arithmetic shift: the sign bit of `x' is replicated
and inserted in the vacated bits. The result is unspecified if
`y < 0' or `y >= 64'.
<<
val shift_right_logical : int64 -> int -> int64
>>
`Int64.shift_right_logical x y' shifts `x' to the right by `y'
bits. This is a logical shift: zeroes are inserted in the
vacated bits regardless of the sign of `x'. The result is
unspecified if `y < 0' or `y >= 64'.
<<
val of_int : int -> int64
>>
Convert the given integer (type `int') to a 64-bit integer
(type `int64').
<<
val to_int : int64 -> int
>>
Convert the given 64-bit integer (type `int64') to an integer
(type `int'). On 64-bit platforms, the 64-bit integer is taken
modulo 2^63, i.e. the high-order bit is lost during the
conversion. On 32-bit platforms, the 64-bit integer is taken
modulo 2^31, i.e. the top 33 bits are lost during the
conversion.
<<
val of_float : float -> int64
>>
Convert the given floating-point number to a 64-bit integer,
discarding the fractional part (truncate towards 0). The result
of the conversion is undefined if, after truncation, the number
is outside the range `Int64.min_int, Int64.max_int'.
<<
val to_float : int64 -> float
>>
Convert the given 64-bit integer to a floating-point number.
<<
val of_int32 : int32 -> int64
>>
Convert the given 32-bit integer (type `int32') to a 64-bit
integer (type `int64').
<<
val to_int32 : int64 -> int32
>>
Convert the given 64-bit integer (type `int64') to a 32-bit
integer (type `int32'). The 64-bit integer is taken modulo 2^32,
i.e. the top 32 bits are lost during the conversion.
<<
val of_nativeint : nativeint -> int64
>>
Convert the given native integer (type `nativeint') to a 64-bit
integer (type `int64').
<<
val to_nativeint : int64 -> nativeint
>>
Convert the given 64-bit integer (type `int64') to a native
integer. On 32-bit platforms, the 64-bit integer is taken modulo
2^32. On 64-bit platforms, the conversion is exact.
<<
val of_string : string -> int64
>>
Convert the given string to a 64-bit integer. The string is
read in decimal (by default) or in hexadecimal, octal or binary
if the string begins with `0x', `0o' or `0b' respectively. Raise
`Failure "int_of_string"' if the given string is not a valid
representation of an integer.
<<
val to_string : int64 -> string
>>
Return the string representation of its argument, in decimal.
<<
val format : string -> int64 -> string
>>
`Int64.format fmt n' return the string representation of the
64-bit integer `n' in the format specified by `fmt'. `fmt' is a
`Printf'-style format containing exactly one `%d', `%i', `%u',
`%x', `%X' or `%o' conversion specification. See the
documentation of the `Printf' module for more information,
<<
val bits_of_float : float -> int64
>>
Return the internal representation of the given float according
to the IEEE 754 floating-point ``double format'' bit layout. Bit
63 of the result represents the sign of the float; bits 62 to 52
represent the (biased) exponent; bits 51 to 0 represent the
mantissa.
<<
val float_of_bits : int64 -> float
>>
Return the floating-point number whose internal representation,
according to the IEEE 754 floating-point ``double format'' bit
layout, is the given `int64'.
19.14 Module Lazy: deferred computations.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
<<
type 'a status =
| Delayed of (unit -> 'a)
| Value of 'a
| Exception of exn
;;
type 'a t = 'a status ref;;
>>
A value of type `'a Lazy.t' is a deferred computation (also
called a suspension) that computes a result of type `'a'. The
expression `lazy (expr)' returns a suspension that computes
`expr'.
<<
exception Undefined;;
val force: 'a t -> 'a;;
>>
`Lazy.force x' computes the suspension `x' and returns its
result. If the suspension was already computed, `Lazy.force x'
returns the same value again. If it raised an exception, the
same exception is raised again. Raise `Undefined' if the
evaluation of the suspension requires its own result.
19.15 Module Lexing: the run-time library for lexers generated by ocamllex
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Lexer buffers
==============
<<
type lexbuf =
{ refill_buff : lexbuf -> unit;
mutable lex_buffer : string;
mutable lex_buffer_len : int;
mutable lex_abs_pos : int;
mutable lex_start_pos : int;
mutable lex_curr_pos : int;
mutable lex_last_pos : int;
mutable lex_last_action : int;
mutable lex_eof_reached : bool }
>>
The type of lexer buffers. A lexer buffer is the argument
passed to the scanning functions defined by the generated
scanners. The lexer buffer holds the current state of the
scanner, plus a function to refill the buffer from the input.
<<
val from_channel : in_channel -> lexbuf
>>
Create a lexer buffer on the given input channel.
`Lexing.from_channel inchan' returns a lexer buffer which reads
from the input channel `inchan', at the current reading
position.
<<
val from_string : string -> lexbuf
>>
Create a lexer buffer which reads from the given string.
Reading starts from the first character in the string. An
end-of-input condition is generated when the end of the string
is reached.
<<
val from_function : (buf:string -> len:int -> int) -> lexbuf
>>
Create a lexer buffer with the given function as its reading
method. When the scanner needs more characters, it will call the
given function, giving it a character string `s' and a character
count `n'. The function should put `n' characters or less in
`s', starting at character number 0, and return the number of
characters provided. A return value of 0 means end of input.
Functions for lexer semantic actions
=====================================
The following functions can be called from the semantic actions
of lexer definitions (the ML code enclosed in braces that
computes the value returned by lexing functions). They give
access to the character string matched by the regular expression
associated with the semantic action. These functions must be
applied to the argument `lexbuf', which, in the code generated
by `ocamllex', is bound to the lexer buffer passed to the
parsing function.
<<
val lexeme : lexbuf -> string
>>
`Lexing.lexeme lexbuf' returns the string matched by the
regular expression.
<<
val lexeme_char : lexbuf -> int -> char
>>
`Lexing.lexeme_char lexbuf i' returns character number `i' in
the matched string.
<<
val lexeme_start : lexbuf -> int
>>
`Lexing.lexeme_start lexbuf' returns the position in the input
stream of the first character of the matched string. The first
character of the stream has position 0.
<<
val lexeme_end : lexbuf -> int
>>
`Lexing.lexeme_end lexbuf' returns the position in the input
stream of the character following the last character of the
matched string. The first character of the stream has position
0.
19.16 Module List: list operations
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Some functions are flagged as not tail-recursive. A
tail-recursive function uses constant stack space, while a
non-tail-recursive function uses stack space proportional to the
length of its list argument, which can be a problem with very
long lists. When the function takes several list arguments, an
approximate formula giving stack usage (in some unspecified
constant unit) is shown in parentheses.
The above considerations can usually be ignored if your lists
are not longer than about 10000 elements.
<<
val length : 'a list -> int
>>
Return the length (number of elements) of the given list.
<<
val hd : 'a list -> 'a
>>
Return the first element of the given list. Raise `Failure
"hd"' if the list is empty.
<<
val tl : 'a list -> 'a list
>>
Return the given list without its first element. Raise `Failure
"tl"' if the list is empty.
<<
val nth : 'a list -> int -> 'a
>>
Return the n-th element of the given list. The first element
(head of the list) is at position 0. Raise `Failure "nth"' if
the list is too short.
<<
val rev : 'a list -> 'a list
>>
List reversal.
<<
val append : 'a list -> 'a list -> 'a list
>>
Catenate two lists. Same function as the infix operator `@'.
Not tail-recursive (length of the first argument). The `@'
operator is not tail-recursive either.
<<
val rev_append : 'a list -> 'a list -> 'a list
>>
`List.rev_append l1 l2' reverses `l1' and catenates it to `l2'.
This is equivalent to `List.rev l1 @ l2', but `rev_append' is
tail-recursive and more efficient.
<<
val concat : 'a list list -> 'a list
val flatten : 'a list list -> 'a list
>>
Catenate (flatten) a list of lists. Not tail-recursive (length
of the argument + length of the longest sub-list).
Iterators
----------
<<
val iter : f:('a -> unit) -> 'a list -> unit
>>
`List.iter f [a1; ...; an]' applies function `f' in turn to
`a1; ...; an'. It is equivalent to `begin f a1; f a2; ...; f an;
() end'.
<<
val map : f:('a -> 'b) -> 'a list -> 'b list
>>
`List.map f [a1; ...; an]' applies function `f' to `a1, ...,
an', and builds the list `[f a1; ...; f an]' with the results
returned by `f'. Not tail-recursive.
<<
val rev_map : f:('a -> 'b) -> 'a list -> 'b list
>>
`List.rev_map f l' gives the same result as `List.rev (List.map
f l)', but is tail-recursive and more efficient.
<<
val fold_left : f:('a -> 'b -> 'a) -> init:'a -> 'b list -> 'a
>>
`List.fold_left f a [b1; ...; bn]' is `f (... (f (f a b1) b2)
...) bn'.
<<
val fold_right : f:('a -> 'b -> 'b) -> 'a list -> init:'b -> 'b
>>
`List.fold_right f [a1; ...; an] b' is `f a1 (f a2 (... (f an
b) ...))'. Not tail-recursive.
Iterators on two lists
-----------------------
<<
val iter2 : f:('a -> 'b -> unit) -> 'a list -> 'b list -> unit
>>
`List.iter2 f [a1; ...; an] [b1; ...; bn]' calls in turn `f a1
b1; ...; f an bn'. Raise `Invalid_argument' if the two lists
have different lengths.
<<
val map2 : f:('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
>>
`List.map2 f [a1; ...; an] [b1; ...; bn]' is `[f a1 b1; ...; f
an bn]'. Raise `Invalid_argument' if the two lists have
different lengths. Not tail-recursive.
<<
val rev_map2 : f:('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
>>
`List.rev_map2 f l' gives the same result as `List.rev
(List.map2 f l)', but is tail-recursive and more efficient.
<<
val fold_left2 :
f:('a -> 'b -> 'c -> 'a) -> init:'a -> 'b list -> 'c list -> 'a
>>
`List.fold_left2 f a [b1; ...; bn] [c1; ...; cn]' is `f (... (f
(f a b1 c1) b2 c2) ...) bn cn'. Raise `Invalid_argument' if the
two lists have different lengths.
<<
val fold_right2 :
f:('a -> 'b -> 'c -> 'c) -> 'a list -> 'b list -> init:'c -> 'c
>>
`List.fold_right2 f [a1; ...; an] [b1; ...; bn] c' is `f a1 b1
(f a2 b2 (... (f an bn c) ...))'. Raise `Invalid_argument' if
the two lists have different lengths. Not tail-recursive.
List scanning
--------------
<<
val for_all : f:('a -> bool) -> 'a list -> bool
>>
`for_all p [a1; ...; an]' checks if all elements of the list
satisfy the predicate `p'. That is, it returns `(p a1) && (p a2)
&& ... && (p an)'.
<<
val exists : f:('a -> bool) -> 'a list -> bool
>>
`exists p [a1; ...; an]' checks if at least one element of the
list satisfies the predicate `p'. That is, it returns `(p a1) ||
(p a2) || ... || (p an)'.
<<
val for_all2 : f:('a -> 'b -> bool) -> 'a list -> 'b list -> bool
val exists2 : f:('a -> 'b -> bool) -> 'a list -> 'b list -> bool
>>
Same as `for_all' and `exists', but for a two-argument
predicate. Raise `Invalid_argument' if the two lists have
different lengths.
<<
val mem : 'a -> 'a list -> bool
>>
`mem a l' is true if and only if `a' is equal to an element of
`l'.
<<
val memq : 'a -> 'a list -> bool
>>
Same as `mem', but uses physical equality instead of structural
equality to compare list elements.
List searching
---------------
<<
val find : f:('a -> bool) -> 'a list -> 'a
>>
`find p l' returns the first element of the list `l' that
satisfies the predicate `p'. Raise `Not_found' if there is no
value that satisfies `p' in the list `l'.
<<
val filter : f:('a -> bool) -> 'a list -> 'a list
val find_all : f:('a -> bool) -> 'a list -> 'a list
>>
`filter p l' returns all the elements of the list `l' that
satisfy the predicate `p'. The order of the elements in the
input list is preserved. `find_all' is another name for
`filter'.
<<
val partition : f:('a -> bool) -> 'a list -> 'a list * 'a list
>>
`partition p l' returns a pair of lists `(l1, l2)', where `l1'
is the list of all the elements of `l' that satisfy the
predicate `p', and `l2' is the list of all the elements of `l'
that do not satisfy `p'. The order of the elements in the input
list is preserved.
Association lists
------------------
<<
val assoc : 'a -> ('a * 'b) list -> 'b
>>
`assoc a l' returns the value associated with key `a' in the
list of pairs `l'. That is, `assoc a [ ...; (a,b); ...] = b' if
`(a,b)' is the leftmost binding of `a' in list `l'. Raise
`Not_found' if there is no value associated with `a' in the list
`l'.
<<
val assq : 'a -> ('a * 'b) list -> 'b
>>
Same as `assoc', but uses physical equality instead of
structural equality to compare keys.
<<
val mem_assoc : 'a -> ('a * 'b) list -> bool
>>
Same as `assoc', but simply return true if a binding exists,
and false if no bindings exist for the given key.
<<
val mem_assq : 'a -> ('a * 'b) list -> bool
>>
Same as `mem_assoc', but uses physical equality instead of
structural equality to compare keys.
<<
val remove_assoc : 'a -> ('a * 'b) list -> ('a * 'b) list
>>
`remove_assoc a l' returns the list of pairs `l' without the
first pair with key `a', if any. Not tail-recursive.
<<
val remove_assq : 'a -> ('a * 'b) list -> ('a * 'b) list
>>
Same as `remove_assq', but uses physical equality instead of
structural equality to compare keys. Not tail-recursive.
Lists of pairs
---------------
<<
val split : ('a * 'b) list -> 'a list * 'b list
>>
Transform a list of pairs into a pair of lists: `split
[(a1,b1); ...; (an,bn)]' is `([a1; ...; an], [b1; ...; bn])'.
Not tail-recursive.
<<
val combine : 'a list -> 'b list -> ('a * 'b) list
>>
Transform a pair of lists into a list of pairs: `combine ([a1;
...; an], [b1; ...; bn])' is `[(a1,b1); ...; (an,bn)]'. Raise
`Invalid_argument' if the two lists have different lengths. Not
tail-recursive.
Sorting
--------
<<
val sort : cmp:('a -> 'a -> int) -> 'a list -> 'a list;;
>>
Sort a list in increasing order according to a comparison
function. The comparison function must return 0 if it arguments
compare as equal, a positive integer if the first is greater,
and a negative integer if the first is smaller. For example, the
`compare' function is a suitable comparison function. The
resulting list is sorted in increasing order. `List.sort' is
guaranteed to run in constant heap space (in addition to the
size of the result list) and logarithmic stack space.
The current implementation uses Merge Sort and is the same as
`List.stable_sort'.
<<
val stable_sort : cmp:('a -> 'a -> int) -> 'a list -> 'a list;;
>>
Same as `List.sort', but the sorting algorithm is stable.
The current implementation is Merge Sort. It runs in constant
heap space and logarithmic stack space.
19.17 Module Map: association tables over ordered types
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module implements applicative association tables, also
known as finite maps or dictionaries, given a total ordering
function over the keys. All operations over maps are purely
applicative (no side-effects). The implementation uses balanced
binary trees, and therefore searching and insertion take time
logarithmic in the size of the map.
<<
module type OrderedType =
sig
type t
val compare: t -> t -> int
end
>>
The input signature of the functor `Map.Make'. `t' is the type
of the map keys. `compare' is a total ordering function over the
keys. This is a two-argument function `f' such that `f e1 e2' is
zero if the keys `e1' and `e2' are equal, `f e1 e2' is strictly
negative if `e1' is smaller than `e2', and `f e1 e2' is strictly
positive if `e1' is greater than `e2'. Example: a suitable
ordering function is the generic structural comparison function
`compare'.
<<
module type S =
sig
type key
>>
The type of the map keys.
<<
type (+'a) t
>>
The type of maps from type `key' to type `'a'.
<<
val empty: 'a t
>>
The empty map.
<<
val add: key:key -> data:'a -> 'a t -> 'a t
>>
`add x y m' returns a map containing the same bindings as `m',
plus a binding of `x' to `y'. If `x' was already bound in `m',
its previous binding disappears.
<<
val find: key -> 'a t -> 'a
>>
`find x m' returns the current binding of `x' in `m', or raises
`Not_found' if no such binding exists.
<<
val remove: key -> 'a t -> 'a t
>>
`remove x m' returns a map containing the same bindings as `m',
except for `x' which is unbound in the returned map.
<<
val mem: key -> 'a t -> bool
>>
`mem x m' returns `true' if `m' contains a binding for `m', and
`false' otherwise.
<<
val iter: f:(key:key -> data:'a -> unit) -> 'a t -> unit
>>
`iter f m' applies `f' to all bindings in map `m'. `f' receives
the key as first argument, and the associated value as second
argument. The order in which the bindings are passed to `f' is
unspecified. Only current bindings are presented to `f':
bindings hidden by more recent bindings are not passed to `f'.
<<
val map: f:('a -> 'b) -> 'a t -> 'b t
>>
`map f m' returns a map with same domain as `m', where the
associated value `a' of all bindings of `m' has been replaced by
the result of the application of `f' to `a'. The order in which
the associated values are passed to `f' is unspecified.
<<
val mapi: f:(key -> 'a -> 'b) -> 'a t -> 'b t
>>
Same as `map', but the function receives as arguments both the
key and the associated value for each binding of the map.
<<
val fold: f:(key:key -> data:'a -> 'b -> 'b) -> 'a t -> init:'b -> 'b
>>
`fold f m a' computes `(f kN dN ... (f k1 d1 a)...)', where `k1
... kN' are the keys of all bindings in `m', and `d1 ... dN' are
the associated data. The order in which the bindings are
presented to `f' is unspecified.
<<
end
module Make(Ord: OrderedType): (S with type key = Ord.t)
>>
Functor building an implementation of the map structure given a
totally ordered type.
19.18 Module Marshal: marshaling of data structures
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module provides functions to encode arbitrary data
structures as sequences of bytes, which can then be written on a
file or sent over a pipe or network connection. The bytes can
then be read back later, possibly in another process, and
decoded back into a data structure. The format for the byte
sequences is compatible across all machines for a given version
of Objective Caml.
Warning: marshaling is currently not type-safe. The type of
marshaled data is not transmitted along the value of the data,
making it impossible to check that the data read back possesses
the type expected by the context. In particular, the result type
of the `Marshal.from_*' functions is given as `'a', but this is
misleading: the returned Caml value does not possess type `'a'
for all `'a'; it has one, unique type which cannot be determined
at compile-type. The programmer should explicitly give the
expected type of the returned value, using the following syntax:
`(Marshal.from_channel chan : type)'. Anything can happen at
run-time if the object in the file does not belong to the given
type.
The representation of marshaled values is not human-readable,
and uses bytes that are not printable characters. Therefore,
input and output channels used in conjunction with
`Marshal.to_channel' and `Marshal.from_channel' must be opened
in binary mode, using e.g. `open_out_bin' or `open_in_bin';
channels opened in text mode will cause unmarshaling errors on
platforms where text channels behave differently than binary
channels, e.g. Windows.
<<
type extern_flags =
No_sharing (* Don't preserve sharing *)
| Closures (* Send function closures *)
>>
The flags to the `Marshal.to_*' functions below.
<<
val to_channel: out_channel -> 'a -> mode:extern_flags list -> unit
>>
`Marshal.to_channel chan v flags' writes the representation of
`v' on channel `chan'. The `flags' argument is a possibly empty
list of flags that governs the marshaling behavior with respect
to sharing and functional values.
If `flags' does not contain `Marshal.No_sharing', circularities
and sharing inside the value `v' are detected and preserved in
the sequence of bytes produced. In particular, this guarantees
that marshaling always terminates. Sharing between values
marshaled by successive calls to `Marshal.to_channel' is not
detected, though. If `flags' contains `Marshal.No_sharing',
sharing is ignored. This results in faster marshaling if `v'
contains no shared substructures, but may cause slower
marshaling and larger byte representations if `v' actually
contains sharing, or even non-termination if `v' contains
cycles.
If `flags' does not contain `Marshal.Closures', marshaling fails
when it encounters a functional value inside `v': only ``pure''
data structures, containing neither functions nor objects, can
safely be transmitted between different programs. If `flags'
contains `Marshal.Closures', functional values will be marshaled
as a position in the code of the program. In this case, the
output of marshaling can only be read back in processes that run
exactly the same program, with exactly the same compiled code.
(This is checked at un-marshaling time, using an MD5 digest of
the code transmitted along with the code position.)
<<
val to_string: 'a -> mode:extern_flags list -> string
>>
`Marshal.to_string v flags' returns a string containing the
representation of `v' as a sequence of bytes. The `flags'
argument has the same meaning as for `Marshal.to_channel'.
<<
val to_buffer: string -> pos:int -> len:int ->
'a -> mode:extern_flags list -> int
>>
`Marshal.to_buffer buff ofs len v flags' marshals the value
`v', storing its byte representation in the string `buff',
starting at character number `ofs', and writing at most `len'
characters. It returns the number of characters actually written
to the string. If the byte representation of `v' does not fit in
`len' characters, the exception `Failure' is raised.
<<
val from_channel: in_channel -> 'a
>>
`Marshal.from_channel chan' reads from channel `chan' the byte
representation of a structured value, as produced by one of the
`Marshal.to_*' functions, and reconstructs and returns the
corresponding value.
<<
val from_string: string -> pos:int -> 'a
>>
`Marshal.from_string buff ofs' unmarshals a structured value
like `Marshal.from_channel' does, except that the byte
representation is not read from a channel, but taken from the
string `buff', starting at position `ofs'.
<<
val header_size : int
val data_size : string -> pos:int -> int
val total_size : string -> pos:int -> int
>>
The bytes representing a marshaled value are composed of a
fixed-size header and a variable-sized data part, whose size can
be determined from the header. `Marshal.header_size' is the
size, in characters, of the header. `Marshal.data_size buff ofs'
is the size, in characters, of the data part, assuming a valid
header is stored in `buff' starting at position `ofs'. Finally,
`Marshal.total_size buff ofs' is the total size, in characters,
of the marshaled value. Both `Marshal.data_size' and
`Marshal.total_size' raise `Failure' if `buff', `ofs' does not
contain a valid header.
To read the byte representation of a marshaled value into a
string buffer, the program needs to read first
`Marshal.header_size' characters into the buffer, then determine
the length of the remainder of the representation using
`Marshal.data_size', make sure the buffer is large enough to
hold the remaining data, then read it, and finally call
`Marshal.from_string' to unmarshal the value.
19.19 Module Nativeint: processor-native integers
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module provides operations on the type `nativeint' of
signed 32-bit integers (on 32-bit platforms) or signed 64-bit
integers (on 64-bit platforms). This integer type has exactly
the same width as that of a `long' integer type in the C
compiler. All arithmetic operations over `nativeint' are taken
modulo 2^32 or 2^64 depending on the word size of the
architecture.
Performance notice: values of type `nativeint' occupy more
memory space than values of type `int', and arithmetic
operations on `nativeint' are generally slower than those on
`int'. Use `nativeint' only when the application requires the
extra bit of precision over the `int' type.
<<
val zero: nativeint
val one: nativeint
val minus_one: nativeint
>>
The native integers 0, 1, -1.
<<
val neg: nativeint -> nativeint
>>
Unary negation.
<<
val add: nativeint -> nativeint -> nativeint
>>
Addition.
<<
val sub: nativeint -> nativeint -> nativeint
>>
Subtraction.
<<
val mul: nativeint -> nativeint -> nativeint
>>
Multiplication.
<<
val div: nativeint -> nativeint -> nativeint
>>
Integer division. Raise `Division_by_zero' if the second
argument is zero.
<<
val rem: nativeint -> nativeint -> nativeint
>>
Integer remainder. If `x >= 0' and `y > 0', the result of
`Nativeint.rem x y' satisfies the following properties: `0 <=
Nativeint.rem x y < y' and `x = Nativeint.add (Nativeint.mul
(Nativeint.div x y) y) (Nativeint.rem x y)'. If `y = 0',
`Nativeint.rem x y' raises `Division_by_zero'. If `x < 0' or `y
< 0', the result of `Nativeint.rem x y' is not specified and
depends on the platform.
<<
val succ: nativeint -> nativeint
>>
Successor. `Nativeint.succ x' is `Nativeint.add x
Nativeint.one'.
<<
val pred: nativeint -> nativeint
>>
Predecessor. `Nativeint.pred x' is `Nativeint.sub x
Nativeint.one'.
<<
val abs: nativeint -> nativeint
>>
Return the absolute value of its argument.
<<
val size: int
>>
The size in bits of a native integer. This is equal to `32' on
a 32-bit platform and to `64' on a 64-bit platform.
<<
val max_int: nativeint
>>
The greatest representable native integer, either 2^31 - 1 on a
32-bit platform, or 2^63 - 1 on a 64-bit platform.
<<
val min_int: nativeint
>>
The greatest representable native integer, either -2^31 on a
32-bit platform, or -2^63 on a 64-bit platform.
<<
val logand: nativeint -> nativeint -> nativeint
>>
Bitwise logical and.
<<
val logor: nativeint -> nativeint -> nativeint
>>
Bitwise logical or.
<<
val logxor: nativeint -> nativeint -> nativeint
>>
Bitwise logical exclusive or.
<<
val lognot: nativeint -> nativeint
>>
Bitwise logical negation
<<
val shift_left: nativeint -> int -> nativeint
>>
`Nativeint.shift_left x y' shifts `x' to the left by `y' bits.
The result is unspecified if `y < 0' or `y >= bitsize', where
`bitsize' is `32' on a 32-bit platform and `64' on a 64-bit
platform.
<<
val shift_right: nativeint -> int -> nativeint
>>
`Nativeint.shift_right x y' shifts `x' to the right by `y'
bits. This is an arithmetic shift: the sign bit of `x' is
replicated and inserted in the vacated bits. The result is
unspecified if `y < 0' or `y >= bitsize'.
<<
val shift_right_logical: nativeint -> int -> nativeint
>>
`Nativeint.shift_right_logical x y' shifts `x' to the right by
`y' bits. This is a logical shift: zeroes are inserted in the
vacated bits regardless of the sign of `x'. The result is
unspecified if `y < 0' or `y >= bitsize'.
<<
val of_int: int -> nativeint
>>
Convert the given integer (type `int') to a native integer
(type `nativeint').
<<
val to_int: nativeint -> int
>>
Convert the given native integer (type `nativeint') to an
integer (type `int'). The high-order bit is lost during the
conversion.
<<
val of_float : float -> nativeint
>>
Convert the given floating-point number to a native integer,
discarding the fractional part (truncate towards 0). The result
of the conversion is undefined if, after truncation, the number
is outside the range `Nativeint.min_int, Nativeint.max_int'.
<<
val to_float : nativeint -> float
>>
Convert the given native integer to a floating-point number.
<<
val of_int32: int32 -> nativeint
>>
Convert the given 32-bit integer (type `int32') to a native
integer.
<<
val to_int32: nativeint -> int32
>>
Convert the given native integer to a 32-bit integer (type
`int32'). On 64-bit platforms, the 64-bit native integer is
taken modulo 2^32, i.e. the top 32 bits are lost. On 32-bit
platforms, the conversion is exact.
<<
val of_string: string -> nativeint
>>
Convert the given string to a native integer. The string is
read in decimal (by default) or in hexadecimal, octal or binary
if the string begins with `0x', `0o' or `0b' respectively. Raise
`Failure "int_of_string"' if the given string is not a valid
representation of an integer.
<<
val to_string: nativeint -> string
>>
Return the string representation of its argument, in decimal.
<<
val format : string -> nativeint -> string
>>
`Nativeint.format fmt n' return the string representation of
the native integer `n' in the format specified by `fmt'. `fmt'
is a `Printf'-style format containing exactly one `%d', `%i',
`%u', `%x', `%X' or `%o' conversion specification. See the
documentation of the `Printf' module for more information,
19.20 Module Oo: object-oriented extension
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
val copy : (< .. > as 'a) -> 'a
>>
`Oo.copy o' returns a copy of object `o', that is a fresh
object with the same methods and instance variables as `o'
19.21 Module Parsing: the run-time library for parsers generated by ocamlyacc
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
<<
val symbol_start : unit -> int
val symbol_end : unit -> int
>>
`symbol_start' and `symbol_end' are to be called in the action
part of a grammar rule only. They return the position of the
string that matches the left-hand side of the rule:
`symbol_start()' returns the position of the first character;
`symbol_end()' returns the position of the last character, plus
one. The first character in a file is at position 0.
<<
val rhs_start: int -> int
val rhs_end: int -> int
>>
Same as `symbol_start' and `symbol_end', but return the
position of the string matching the `n'th item on the right-hand
side of the rule, where `n' is the integer parameter to
`lhs_start' and `lhs_end'. `n' is 1 for the leftmost item.
<<
val clear_parser : unit -> unit
>>
Empty the parser stack. Call it just after a parsing function
has returned, to remove all pointers from the parser stack to
structures that were built by semantic actions during parsing.
This is optional, but lowers the memory requirements of the
programs.
<<
exception Parse_error
>>
Raised when a parser encounters a syntax error. Can also be
raised from the action part of a grammar rule, to initiate error
recovery.
19.22 Module Printexc: a catch-all exception handler
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
val catch: ('a -> 'b) -> 'a -> 'b
>>
`Printexc.catch fn x' applies `fn' to `x' and returns the
result. If the evaluation of `fn x' raises any exception, the
name of the exception is printed on standard error output, and
the programs aborts with exit code 2. Typical use is
`Printexc.catch main ()', where `main', with type `unit->unit',
is the entry point of a standalone program. This catches and
reports any exception that escapes the program.
<<
val print: ('a -> 'b) -> 'a -> 'b
>>
Same as `catch', but re-raise the stray exception after
printing it, instead of aborting the program.
<<
val to_string : exn -> string
>>
`Printexc.to_string e' returns a string representation of `e'.
19.23 Module Printf: formatting printing functions
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
val fprintf: out_channel -> ('a, out_channel, unit) format -> 'a
>>
`fprintf outchan format arg1 ... argN' formats the arguments
`arg1' to `argN' according to the format string `format', and
outputs the resulting string on the channel `outchan'.
The format is a character string which contains two types of
objects: plain characters, which are simply copied to the output
channel, and conversion specifications, each of which causes
conversion and printing of one argument.
Conversion specifications consist in the `%' character, followed
by optional flags and field widths, followed by one conversion
character. The conversion characters and their meanings are:
`d' or `i': convert an integer argument to signed decimal
`u': convert an integer argument to unsigned decimal
`x': convert an integer argument to unsigned hexadecimal, using
lowercase letters.
`X': convert an integer argument to unsigned hexadecimal, using
uppercase letters.
`o': convert an integer argument to unsigned octal.
`s': insert a string argument
`c': insert a character argument
`f': convert a floating-point argument to decimal notation, in
the style `dddd.ddd'
`e' or `E': convert a floating-point argument to decimal
notation, in the style `d.ddd e+-dd' (mantissa and exponent)
`g' or `G': convert a floating-point argument to decimal
notation, in style `f' or `e', `E' (whichever is more compact)
`b': convert a boolean argument to the string `true' or `false'
`a': user-defined printer. Takes two arguments and apply the
first one to `outchan' (the current output channel) and to the
second argument. The first argument must therefore have type
`out_channel -> 'b -> unit' and the second `'b'. The output
produced by the function is therefore inserted in the output of
`fprintf' at the current point.
`t': same as `%a', but takes only one argument (with type
`out_channel -> unit') and apply it to `outchan'.
`%': take no argument and output one `%' character.
Refer to the C library `printf' function for the meaning of
flags and field width specifiers.
Warning: if too few arguments are provided, for instance because
the `printf' function is partially applied, the format is
immediately printed up to the conversion of the first missing
argument; printing will then resume when the missing arguments
are provided. For example, `List.iter (printf "x=%d y=%d " 1)
[2;3]' prints `x=1 y=2 3' instead of the expected `x=1 y=2 x=1
y=3'. To get the expected behavior, do `List.iter (fun y ->
printf "x=%d y=%d " 1 y) [2;3]'.
<<
val printf: ('a, out_channel, unit) format -> 'a
>>
Same as `fprintf', but output on `stdout'.
<<
val eprintf: ('a, out_channel, unit) format -> 'a
>>
Same as `fprintf', but output on `stderr'.
<<
val sprintf: ('a, unit, string) format -> 'a
>>
Same as `fprintf', but instead of printing on an output
channel, return a string containing the result of formatting the
arguments.
<<
val bprintf: Buffer.t -> ('a, Buffer.t, unit) format -> 'a
>>
Same as `fprintf', but instead of printing on an output
channel, append the formatted arguments to the given extensible
buffer (see module `Buffer').
19.24 Module Queue: first-in first-out queues
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module implements queues (FIFOs), with in-place
modification.
<<
type 'a t
>>
The type of queues containing elements of type `'a'.
<<
exception Empty
>>
Raised when `take' is applied to an empty queue.
<<
val create: unit -> 'a t
>>
Return a new queue, initially empty.
<<
val add: 'a -> 'a t -> unit
>>
`add x q' adds the element `x' at the end of the queue `q'.
<<
val take: 'a t -> 'a
>>
`take q' removes and returns the first element in queue `q', or
raises `Empty' if the queue is empty.
<<
val peek: 'a t -> 'a
>>
`peek q' returns the first element in queue `q', without
removing it from the queue, or raises `Empty' if the queue is
empty.
<<
val clear : 'a t -> unit
>>
Discard all elements from a queue.
<<
val length: 'a t -> int
>>
Return the number of elements in a queue.
<<
val iter: f:('a -> unit) -> 'a t -> unit
>>
`iter f q' applies `f' in turn to all elements of `q', from the
least recently entered to the most recently entered. The queue
itself is unchanged.
19.25 Module Random: pseudo-random number generator (PRNG)
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
val init : int -> unit
>>
Initialize the generator, using the argument as a seed. The
same seed will always yield the same sequence of numbers.
<<
val full_init : int array -> unit
>>
Same as `init' but takes more data as seed.
<<
val self_init : unit -> unit
>>
Initialize the generator with a more-or-less random seed chosen
in a system-dependent way.
<<
val bits : unit -> int
>>
Return 30 random bits in a nonnegative integer.
<<
val int : int -> int
>>
`Random.int bound' returns a random integer between 0
(inclusive) and `bound' (exclusive). `bound' must be more than 0
and less than 2^30.
<<
val float : float -> float
>>
`Random.float bound' returns a random floating-point number
between 0 (inclusive) and `bound' (exclusive). If `bound' is
negative, the result is negative. If `bound' is 0, the result is
0.
<<
type state;;
>>
Values of this type are used to store the current state of the
generator.
<<
val get_state : unit -> state;;
>>
Returns the current state of the generator. This is useful for
checkpointing computations that use the PRNG.
<<
val set_state : state -> unit;;
>>
Resets the state of the generator to some previous state
returned by `get_state'.
19.26 Module Set: sets over ordered types
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module implements the set data structure, given a total
ordering function over the set elements. All operations over
sets are purely applicative (no side-effects). The
implementation uses balanced binary trees, and is therefore
reasonably efficient: insertion and membership take time
logarithmic in the size of the set, for instance.
<<
module type OrderedType =
sig
type t
val compare: t -> t -> int
end
>>
The input signature of the functor `Set.Make'. `t' is the type
of the set elements. `compare' is a total ordering function over
the set elements. This is a two-argument function `f' such that
`f e1 e2' is zero if the elements `e1' and `e2' are equal, `f e1
e2' is strictly negative if `e1' is smaller than `e2', and `f e1
e2' is strictly positive if `e1' is greater than `e2'. Example:
a suitable ordering function is the generic structural
comparison function `compare'.
<<
module type S =
sig
type elt
>>
The type of the set elements.
<<
type t
>>
The type of sets.
<<
val empty: t
>>
The empty set.
<<
val is_empty: t -> bool
>>
Test whether a set is empty or not.
<<
val mem: elt -> t -> bool
>>
`mem x s' tests whether `x' belongs to the set `s'.
<<
val add: elt -> t -> t
>>
`add x s' returns a set containing all elements of `s', plus
`x'. If `x' was already in `s', `s' is returned unchanged.
<<
val singleton: elt -> t
>>
`singleton x' returns the one-element set containing only `x'.
<<
val remove: elt -> t -> t
>>
`remove x s' returns a set containing all elements of `s',
except `x'. If `x' was not in `s', `s' is returned unchanged.
<<
val union: t -> t -> t
val inter: t -> t -> t
val diff: t -> t -> t
>>
Union, intersection and set difference.
<<
val compare: t -> t -> int
>>
Total ordering between sets. Can be used as the ordering
function for doing sets of sets.
<<
val equal: t -> t -> bool
>>
`equal s1 s2' tests whether the sets `s1' and `s2' are equal,
that is, contain equal elements.
<<
val subset: t -> t -> bool
>>
`subset s1 s2' tests whether the set `s1' is a subset of the
set `s2'.
<<
val iter: f:(elt -> unit) -> t -> unit
>>
`iter f s' applies `f' in turn to all elements of `s'. The
order in which the elements of `s' are presented to `f' is
unspecified.
<<
val fold: f:(elt -> 'a -> 'a) -> t -> init:'a -> 'a
>>
`fold f s a' computes `(f xN ... (f x2 (f x1 a))...)', where
`x1 ... xN' are the elements of `s'. The order in which elements
of `s' are presented to `f' is unspecified.
<<
val for_all: f:(elt -> bool) -> t -> bool
>>
`for_all p s' checks if all elements of the set satisfy the
predicate `p'.
<<
val exists: f:(elt -> bool) -> t -> bool
>>
`exists p s' checks if at least one element of the set
satisfies the predicate `p'.
<<
val filter: f:(elt -> bool) -> t -> t
>>
`filter p s' returns the set of all elements in `s' that
satisfy predicate `p'.
<<
val partition: f:(elt -> bool) -> t -> t * t
>>
`partition p s' returns a pair of sets `(s1, s2)', where `s1'
is the set of all the elements of `s' that satisfy the predicate
`p', and `s2' is the set of all the elements of `s' that do not
satisfy `p'.
<<
val cardinal: t -> int
>>
Return the number of elements of a set.
<<
val elements: t -> elt list
>>
Return the list of all elements of the given set. The returned
list is sorted in increasing order with respect to the ordering
`Ord.compare', where `Ord' is the argument given to `Set.Make'.
<<
val min_elt: t -> elt
>>
Return the smallest element of the given set (with respect to
the `Ord.compare' ordering), or raise `Not_found' if the set is
empty.
<<
val max_elt: t -> elt
>>
Same as `min_elt', but returns the largest element of the given
set.
<<
val choose: t -> elt
>>
Return one element of the given set, or raise `Not_found' if
the set is empty. Which element is chosen is unspecified, but
equal elements will be chosen for equal sets.
<<
end
module Make(Ord: OrderedType): (S with type elt = Ord.t)
>>
Functor building an implementation of the set structure given a
totally ordered type.
19.27 Module Sort: sorting and merging lists
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module is obsolete and exists only for backward
compatibility. The sorting functions in `Array' and `List'
should be used instead. The new functions are faster and use
less memory.
<<
val list : order:('a -> 'a -> bool) -> 'a list -> 'a list
>>
Sort a list in increasing order according to an ordering
predicate. The predicate should return `true' if its first
argument is less than or equal to its second argument.
<<
val array : order:('a -> 'a -> bool) -> 'a array -> unit
>>
Sort an array in increasing order according to an ordering
predicate. The predicate should return `true' if its first
argument is less than or equal to its second argument. The array
is sorted in place.
<<
val merge : order:('a -> 'a -> bool) -> 'a list -> 'a list -> 'a list
>>
Merge two lists according to the given predicate. Assuming the
two argument lists are sorted according to the predicate,
`merge' returns a sorted list containing the elements from the
two lists. The behavior is undefined if the two argument lists
were not sorted.
19.28 Module Stack: last-in first-out stacks
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module implements stacks (LIFOs), with in-place
modification.
<<
type 'a t
>>
The type of stacks containing elements of type `'a'.
<<
exception Empty
>>
Raised when `pop' is applied to an empty stack.
<<
val create: unit -> 'a t
>>
Return a new stack, initially empty.
<<
val push: 'a -> 'a t -> unit
>>
`push x s' adds the element `x' at the top of stack `s'.
<<
val pop: 'a t -> 'a
>>
`pop s' removes and returns the topmost element in stack `s',
or raises `Empty' if the stack is empty.
<<
val top: 'a t -> 'a
>>
`top s' returns the topmost element in stack `s', or raises
`Empty' if the stack is empty.
<<
val clear : 'a t -> unit
>>
Discard all elements from a stack.
<<
val length: 'a t -> int
>>
Return the number of elements in a stack.
<<
val iter: f:('a -> unit) -> 'a t -> unit
>>
`iter f s' applies `f' in turn to all elements of `s', from the
element at the top of the stack to the element at the bottom of
the stack. The stack itself is unchanged.
19.29 Module Stream: streams and parsers
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
type 'a t
>>
The type of streams holding values of type `'a'.
<<
exception Failure;;
>>
Raised by parsers when none of the first components of the
stream patterns is accepted.
<<
exception Error of string;;
>>
Raised by parsers when the first component of a stream pattern
is accepted, but one of the following components is rejected.
Stream builders
----------------
Warning: these functions create streams with fast access; it is
illegal to mix them with streams built with `[< >]'; would raise
`Failure' when accessing such mixed streams.
<<
val from : (int -> 'a option) -> 'a t;;
>>
`Stream.from f' returns a stream built from the function `f'.
To create a new stream element, the function `f' is called with
the current stream count. The user function `f' must return
either `Some <value>' for a value or `None' to specify the end
of the stream.
<<
val of_list : 'a list -> 'a t;;
>>
Return the stream holding the elements of the list in the same
order.
<<
val of_string : string -> char t;;
>>
Return the stream of the characters of the string parameter.
<<
val of_channel : in_channel -> char t;;
>>
Return the stream of the characters read from the input
channel.
Stream iterator
----------------
<<
val iter : f:('a -> unit) -> 'a t -> unit;;
>>
`Stream.iter f s' scans the whole stream s, applying function
`f' in turn to each stream element encountered.
Predefined parsers
-------------------
<<
val next : 'a t -> 'a;;
>>
Return the first element of the stream and remove it from the
stream. Raise `Stream.Failure' if the stream is empty.
<<
val empty : 'a t -> unit;;
>>
Return `()' if the stream is empty, else raise
`Stream.Failure'.
Useful functions
-----------------
<<
val peek : 'a t -> 'a option;;
>>
Return `Some' of "the first element" of the stream, or `None'
if the stream is empty.
<<
val junk : 'a t -> unit;;
>>
Remove the first element of the stream, possibly unfreezing it
before.
<<
val count : 'a t -> int;;
>>
Return the current count of the stream elements, i.e. the
number of the stream elements discarded.
<<
val npeek : int -> 'a t -> 'a list;;
>>
`npeek n' returns the list of the `n' first elements of the
stream, or all its remaining elements if less than `n' elements
are available.
19.30 Module String: string operations
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
val length : string -> int
>>
Return the length (number of characters) of the given string.
<<
val get : string -> int -> char
>>
`String.get s n' returns character number `n' in string `s'.
The first character is character number 0. The last character is
character number `String.length s - 1'. Raise `Invalid_argument'
if `n' is outside the range 0 to `(String.length s - 1)'. You
can also write `s.[n]' instead of `String.get s n'.
<<
val set : string -> int -> char -> unit
>>
`String.set s n c' modifies string `s' in place, replacing the
character number `n' by `c'. Raise `Invalid_argument' if `n' is
outside the range 0 to `(String.length s - 1)'. You can also
write `s.[n] <- c' instead of `String.set s n c'.
<<
val create : int -> string
>>
`String.create n' returns a fresh string of length `n'. The
string initially contains arbitrary characters. Raise
`Invalid_argument' if `n <= 0' or `n > Sys.max_string_length'.
<<
val make : int -> char -> string
>>
`String.make n c' returns a fresh string of length `n', filled
with the character `c'. Raise `Invalid_argument' if `n <= 0' or
`n > Sys.max_string_length'.
<<
val copy : string -> string
>>
Return a copy of the given string.
<<
val sub : string -> pos:int -> len:int -> string
>>
`String.sub s start len' returns a fresh string of length
`len', containing the characters number `start' to `start + len
- 1' of string `s'. Raise `Invalid_argument' if `start' and
`len' do not designate a valid substring of `s'; that is, if
`start < 0', or `len < 0', or `start + len > String.length s'.
<<
val fill : string -> pos:int -> len:int -> char -> unit
>>
`String.fill s start len c' modifies string `s' in place,
replacing the characters number `start' to `start + len - 1' by
`c'. Raise `Invalid_argument' if `start' and `len' do not
designate a valid substring of `s'.
<<
val blit : src:string -> src_pos:int ->
dst:string -> dst_pos:int -> len:int -> unit
>>
`String.blit src srcoff dst dstoff len' copies `len' characters
from string `src', starting at character number `srcoff', to
string `dst', starting at character number `dstoff'. It works
correctly even if `src' and `dst' are the same string, and the
source and destination chunks overlap. Raise `Invalid_argument'
if `srcoff' and `len' do not designate a valid substring of
`src', or if `dstoff' and `len' do not designate a valid
substring of `dst'.
<<
val concat : sep:string -> string list -> string
>>
`String.concat sep sl' catenates the list of strings `sl',
inserting the separator string `sep' between each.
<<
val escaped: string -> string
>>
Return a copy of the argument, with special characters
represented by escape sequences, following the lexical
conventions of Objective Caml.
<<
val index: string -> char -> int
>>
`String.index s c' returns the position of the leftmost
occurrence of character `c' in string `s'. Raise `Not_found' if
`c' does not occur in `s'.
<<
val rindex: string -> char -> int
>>
`String.rindex s c' returns the position of the rightmost
occurrence of character `c' in string `s'. Raise `Not_found' if
`c' does not occur in `s'.
<<
val index_from: string -> int -> char -> int
val rindex_from: string -> int -> char -> int
>>
Same as `String.index' and `String.rindex', but start searching
at the character position given as second argument.
`String.index s c' is equivalent to `String.index_from s 0 c',
and `String.rindex s c' to `String.rindex_from s (String.length
s - 1) c'.
<<
val contains : string -> char -> bool
>>
`String.contains s c' tests if character `c' appears in the
string `s'.
<<
val contains_from : string -> int -> char -> bool
>>
`String.contains_from s start c' tests if character `c' appears
in the substring of `s' starting from `start' to the end of `s'.
Raise `Invalid_argument' if `start' is not a valid index of `s'.
<<
val rcontains_from : string -> int -> char -> bool
>>
`String.rcontains_from s stop c' tests if character `c' appears
in the substring of `s' starting from the beginning of `s' to
index `stop'. Raise `Invalid_argument' if `stop' is not a valid
index of `s'.
<<
val uppercase: string -> string
>>
Return a copy of the argument, with all lowercase letters
translated to uppercase, including accented letters of the ISO
Latin-1 (8859-1) character set.
<<
val lowercase: string -> string
>>
Return a copy of the argument, with all uppercase letters
translated to lowercase, including accented letters of the ISO
Latin-1 (8859-1) character set.
<<
val capitalize: string -> string
>>
Return a copy of the argument, with the first letter set to
uppercase.
<<
val uncapitalize: string -> string
>>
Return a copy of the argument, with the first letter set to
lowercase.
19.31 Module Sys: system interface
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
val argv: string array
>>
The command line arguments given to the process. The first
element is the command name used to invoke the program. The
following elements are the command-line arguments given to the
program.
<<
val file_exists: string -> bool
>>
Test if a file with the given name exists.
<<
val remove: string -> unit
>>
Remove the given file name from the file system.
<<
val rename : src:string -> dst:string -> unit
>>
Rename a file. The first argument is the old name and the
second is the new name.
<<
val getenv: string -> string
>>
Return the value associated to a variable in the process
environment. Raise `Not_found' if the variable is unbound.
<<
val command: string -> int
>>
Execute the given shell command and return its exit code.
<<
val time: unit -> float
>>
Return the processor time, in seconds, used by the program
since the beginning of execution.
<<
val chdir: string -> unit
>>
Change the current working directory of the process.
<<
val getcwd: unit -> string
>>
Return the current working directory of the process.
<<
val interactive: bool ref
>>
This reference is initially set to `false' in standalone
programs and to `true' if the code is being executed under the
interactive toplevel system `ocaml'.
<<
val os_type: string
>>
Operating system currently executing the Caml program. One of
`"Unix"', `"Win32"', `"Cygwin"' or `"MacOS"'.
<<
val word_size: int
>>
Size of one word on the machine currently executing the Caml
program, in bits: 32 or 64.
<<
val max_string_length: int
>>
Maximum length of a string.
<<
val max_array_length: int
>>
Maximum length of an array.
Signal handling
================
<<
type signal_behavior =
Signal_default
| Signal_ignore
| Signal_handle of (int -> unit)
>>
What to do when receiving a signal:
`Signal_default': take the default behavior (usually: abort the
program)
`Signal_ignore': ignore the signal
`Signal_handle f': call function `f', giving it the signal
number as argument.
<<
val signal: int -> signal_behavior -> signal_behavior
>>
Set the behavior of the system on receipt of a given signal.
The first argument is the signal number. Return the behavior
previously associated with the signal.
<<
val set_signal: int -> signal_behavior -> unit
>>
Same as `signal' but return value is ignored.
<<
val sigabrt: int (* Abnormal termination *)
val sigalrm: int (* Timeout *)
val sigfpe: int (* Arithmetic exception *)
val sighup: int (* Hangup on controlling terminal *)
val sigill: int (* Invalid hardware instruction *)
val sigint: int (* Interactive interrupt (ctrl-C) *)
val sigkill: int (* Termination (cannot be ignored) *)
val sigpipe: int (* Broken pipe *)
val sigquit: int (* Interactive termination *)
val sigsegv: int (* Invalid memory reference *)
val sigterm: int (* Termination *)
val sigusr1: int (* Application-defined signal 1 *)
val sigusr2: int (* Application-defined signal 2 *)
val sigchld: int (* Child process terminated *)
val sigcont: int (* Continue *)
val sigstop: int (* Stop *)
val sigtstp: int (* Interactive stop *)
val sigttin: int (* Terminal read from background process *)
val sigttou: int (* Terminal write from background process *)
val sigvtalrm: int (* Timeout in virtual time *)
val sigprof: int (* Profiling interrupt *)
>>
Signal numbers for the standard POSIX signals.
<<
exception Break
>>
Exception raised on interactive interrupt if `catch_break' is
on.
<<
val catch_break: bool -> unit
>>
`catch_break' governs whether interactive interrupt (ctrl-C)
terminates the program or raises the `Break' exception. Call
`catch_break true' to enable raising `Break', and `catch_break
false' to let the system terminate the program on user
interrupt.
19.32 Module Weak: arrays of weak pointers
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
type 'a t;;
>>
The type of arrays of weak pointers (weak arrays). A weak
pointer is a value that the garbage collector may erase at any
time. A weak pointer is said to be full if it points to a value,
empty if the value was erased by the GC.
<<
val create : int -> 'a t;;
>>
`Weak.create n' returns a new weak array of length `n'. All the
pointers are initially empty. Raise `Invalid_argument' if `n' is
negative or greater than `Sys.max_array_length-1'.
<<
val length : 'a t -> int;;
>>
`Weak.length ar' returns the length (number of elements) of
`ar'.
<<
val set : 'a t -> int -> 'a option -> unit;;
>>
`Weak.set ar n (Some el)' sets the `n'th cell of `ar' to be a
(full) pointer to `el'; `Weak.set ar n None' sets the `n'th cell
of `ar' to empty. Raise `Invalid_argument "Weak.set"' if `n' is
not in the range 0 to `Weak.length a - 1'.
<<
val get : 'a t -> int -> 'a option;;
>>
`Weak.get ar n' returns None if the `n'th cell of `ar' is
empty, `Some x' (where `x' is the value) if it is full. Raise
`Invalid_argument "Weak.get"' if `n' is not in the range 0 to
`Weak.length a - 1'.
<<
val get_copy : 'a t -> int -> 'a option;;
>>
`Weak.get_copy ar n' returns None if the `n'th cell of `ar' is
empty, `Some x' (where `x' is a (shallow) copy of the value) if
it is full. In addition to pitfalls with mutable values, the
interesting difference with `get' is that `get_copy' does not
prevent the incremental GC from erasing the value in its current
cycle (`get' may delay the erasure to the next GC cycle). Raise
`Invalid_argument "Weak.get"' if `n' is not in the range 0 to
`Weak.length a - 1'.
<<
val check: 'a t -> int -> bool;;
>>
`Weak.check ar n' returns `true' if the `n'th cell of `ar' is
full, `false' if it is empty. Note that even if `Weak.check ar
n' returns `true', a subsequent `Weak.get ar n' can return
`None'.
<<
val fill: 'a t -> pos:int -> len:int -> 'a option -> unit;;
>>
`Weak.fill ar ofs len el' sets to `el' all pointers of `ar'
from `ofs' to `ofs + len - 1'. Raise `Invalid_argument
"Weak.fill"' if `ofs' and `len' do not designate a valid
subarray of `a'.
<<
val blit : src:'a t -> src_pos:int ->
dst:'a t -> dst_pos:int -> len:int -> unit;;
>>
`Weak.blit ar1 off1 ar2 off2 len' copies `len' weak pointers
from `ar1' (starting at `off1') to `ar2' (starting at `off2').
It works correctly even if `ar1' and `ar2' are the same. Raise
`Invalid_argument "Weak.blit"' if `off1' and `len' do not
designate a valid subarray of `ar1', or if `off2' and `len' do
not designate a valid subarray of `ar2'.
Chapter 20 The unix library: Unix system calls
**************************************************
The unix library makes many Unix system calls and system-related library
functions available to Objective Caml programs. This chapter describes briefly
the functions provided. Refer to sections 2 and 3 of the Unix manual for more
details on the behavior of these functions.
Not all functions are provided by all Unix variants. If some functions are
not available, they will raise Invalid_arg when called.
Programs that use the unix library must be linked as follows:
<<
ocamlc other options unix.cma other files
ocamlopt other options unix.cmxa other files
>>
For interactive use of the unix library, do:
<<
ocamlmktop -o mytop unix.cma
./mytop
>>
MacOS:
A fairly complete emulation of the Unix system calls is
provided in the MacOS version of Objective Caml. The end of this
chapter gives more information on the functions that are not
supported under MacOS.
Windows:
A fairly complete emulation of the Unix system calls is
provided in the Windows version of Objective Caml. The end of
this chapter gives more information on the functions that are
not supported under Windows.
20.1 Module Unix: interface to the Unix system
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Error report
=============
<<
type error =
>>
Errors defined in the POSIX standard
<<
E2BIG (* Argument list too long *)
| EACCES (* Permission denied *)
| EAGAIN (* Resource temporarily unavailable; try again *)
| EBADF (* Bad file descriptor *)
| EBUSY (* Resource unavailable *)
| ECHILD (* No child process *)
| EDEADLK (* Resource deadlock would occur *)
| EDOM (* Domain error for math functions, etc. *)
| EEXIST (* File exists *)
| EFAULT (* Bad address *)
| EFBIG (* File too large *)
| EINTR (* Function interrupted by signal *)
| EINVAL (* Invalid argument *)
| EIO (* Hardware I/O error *)
| EISDIR (* Is a directory *)
| EMFILE (* Too many open files by the process *)
| EMLINK (* Too many links *)
| ENAMETOOLONG (* Filename too long *)
| ENFILE (* Too many open files in the system *)
| ENODEV (* No such device *)
| ENOENT (* No such file or directory *)
| ENOEXEC (* Not an executable file *)
| ENOLCK (* No locks available *)
| ENOMEM (* Not enough memory *)
| ENOSPC (* No space left on device *)
| ENOSYS (* Function not supported *)
| ENOTDIR (* Not a directory *)
| ENOTEMPTY (* Directory not empty *)
| ENOTTY (* Inappropriate I/O control operation *)
| ENXIO (* No such device or address *)
| EPERM (* Operation not permitted *)
| EPIPE (* Broken pipe *)
| ERANGE (* Result too large *)
| EROFS (* Read-only file system *)
| ESPIPE (* Invalid seek e.g. on a pipe *)
| ESRCH (* No such process *)
| EXDEV (* Invalid link *)
>>
Additional errors, mostly BSD
<<
| EWOULDBLOCK (* Operation would block *)
| EINPROGRESS (* Operation now in progress *)
| EALREADY (* Operation already in progress *)
| ENOTSOCK (* Socket operation on non-socket *)
| EDESTADDRREQ (* Destination address required *)
| EMSGSIZE (* Message too long *)
| EPROTOTYPE (* Protocol wrong type for socket *)
| ENOPROTOOPT (* Protocol not available *)
| EPROTONOSUPPORT (* Protocol not supported *)
| ESOCKTNOSUPPORT (* Socket type not supported *)
| EOPNOTSUPP (* Operation not supported on socket *)
| EPFNOSUPPORT (* Protocol family not supported *)
| EAFNOSUPPORT (* Address family not supported by protocol family *)
| EADDRINUSE (* Address already in use *)
| EADDRNOTAVAIL (* Can't assign requested address *)
| ENETDOWN (* Network is down *)
| ENETUNREACH (* Network is unreachable *)
| ENETRESET (* Network dropped connection on reset *)
| ECONNABORTED (* Software caused connection abort *)
| ECONNRESET (* Connection reset by peer *)
| ENOBUFS (* No buffer space available *)
| EISCONN (* Socket is already connected *)
| ENOTCONN (* Socket is not connected *)
| ESHUTDOWN (* Can't send after socket shutdown *)
| ETOOMANYREFS (* Too many references: can't splice *)
| ETIMEDOUT (* Connection timed out *)
| ECONNREFUSED (* Connection refused *)
| EHOSTDOWN (* Host is down *)
| EHOSTUNREACH (* No route to host *)
| ELOOP (* Too many levels of symbolic links *)
>>
All other errors are mapped to EUNKNOWNERR
<<
| EUNKNOWNERR of int (* Unknown error *)
>>
The type of error codes.
<<
exception Unix_error of error * string * string
>>
Raised by the system calls below when an error is encountered.
The first component is the error code; the second component is
the function name; the third component is the string parameter
to the function, if it has one, or the empty string otherwise.
<<
val error_message : error -> string
>>
Return a string describing the given error code.
<<
val handle_unix_error : ('a -> 'b) -> 'a -> 'b
>>
`handle_unix_error f x' applies `f' to `x' and returns the
result. If the exception `Unix_error' is raised, it prints a
message describing the error and exits with code 2.
Access to the process environment
==================================
<<
val environment : unit -> string array
>>
Return the process environment, as an array of strings with the
format ``variable=value''.
<<
val getenv: string -> string
>>
Return the value associated to a variable in the process
environment. Raise `Not_found' if the variable is unbound. (This
function is identical to `Sys.getenv'.)
<<
val putenv: string -> string -> unit
>>
`Unix.putenv name value' sets the value associated to a
variable in the process environment. `name' is the name of the
environment variable, and `value' its new associated value.
Process handling
=================
<<
type process_status =
WEXITED of int
| WSIGNALED of int
| WSTOPPED of int
>>
The termination status of a process. `WEXITED' means that the
process terminated normally by `exit'; the argument is the
return code. `WSIGNALED' means that the process was killed by a
signal; the argument is the signal number. `WSTOPPED' means that
the process was stopped by a signal; the argument is the signal
number.
<<
type wait_flag =
WNOHANG
| WUNTRACED
>>
Flags for `waitpid'. `WNOHANG' means do not block if no child
has died yet, but immediately return with a pid equal to 0.
`WUNTRACED' means report also the children that receive stop
signals.
<<
val execv : prog:string -> args:string array -> unit
>>
`execv prog args' execute the program in file `prog', with the
arguments `args', and the current process environment.
<<
val execve : prog:string -> args:string array -> env:string array -> unit
>>
Same as `execv', except that the third argument provides the
environment to the program executed.
<<
val execvp : prog:string -> args:string array -> unit
val execvpe : prog:string -> args:string array -> env:string array -> unit
>>
Same as `execv' and `execvp' respectively, except that the
program is searched in the path.
<<
val fork : unit -> int
>>
Fork a new process. The returned integer is 0 for the child
process, the pid of the child process for the parent process.
<<
val wait : unit -> int * process_status
>>
Wait until one of the children processes die, and return its
pid and termination status.
<<
val waitpid : mode:wait_flag list -> int -> int * process_status
>>
Same as `wait', but waits for the process whose pid is given. A
pid of `-1' means wait for any child. A pid of `0' means wait
for any child in the same process group as the current process.
Negative pid arguments represent process groups. The list of
options indicates whether `waitpid' should return immediately
without waiting, or also report stopped children.
<<
val system : string -> process_status
>>
Execute the given command, wait until it terminates, and return
its termination status. The string is interpreted by the shell
`/bin/sh' and therefore can contain redirections, quotes,
variables, etc. The result `WEXITED 127' indicates that the
shell couldn't be executed.
<<
val getpid : unit -> int
>>
Return the pid of the process.
<<
val getppid : unit -> int
>>
Return the pid of the parent process.
<<
val nice : int -> int
>>
Change the process priority. The integer argument is added to
the ``nice'' value. (Higher values of the ``nice'' value mean
lower priorities.) Return the new nice value.
Basic file input/output
========================
<<
type file_descr
>>
The abstract type of file descriptors.
<<
val stdin : file_descr
val stdout : file_descr
val stderr : file_descr
>>
File descriptors for standard input, standard output and
standard error.
<<
type open_flag =
O_RDONLY (* Open for reading *)
| O_WRONLY (* Open for writing *)
| O_RDWR (* Open for reading and writing *)
| O_NONBLOCK (* Open in non-blocking mode *)
| O_APPEND (* Open for append *)
| O_CREAT (* Create if nonexistent *)
| O_TRUNC (* Truncate to 0 length if existing
*)
| O_EXCL (* Fail if existing *)
>>
The flags to `open'.
<<
type file_perm = int
>>
The type of file access rights.
<<
val openfile : string -> mode:open_flag list -> perm:file_perm -> file_descr
>>
Open the named file with the given flags. Third argument is the
permissions to give to the file if it is created. Return a file
descriptor on the named file.
<<
val close : file_descr -> unit
>>
Close a file descriptor.
<<
val read : file_descr -> buf:string -> pos:int -> len:int -> int
>>
`read fd buff ofs len' reads `len' characters from descriptor
`fd', storing them in string `buff', starting at position `ofs'
in string `buff'. Return the number of characters actually read.
<<
val write : file_descr -> buf:string -> pos:int -> len:int -> int
>>
`write fd buff ofs len' writes `len' characters to descriptor
`fd', taking them from string `buff', starting at position `ofs'
in string `buff'. Return the number of characters actually
written.
Interfacing with the standard input/output library.
====================================================
<<
val in_channel_of_descr : file_descr -> in_channel
>>
Create an input channel reading from the given descriptor. The
channel is initially in binary mode; use `set_binary_mode_in ic
false' if text mode is desired.
<<
val out_channel_of_descr : file_descr -> out_channel
>>
Create an output channel writing on the given descriptor. The
channel is initially in binary mode; use `set_binary_mode_out oc
false' if text mode is desired.
<<
val descr_of_in_channel : in_channel -> file_descr
>>
Return the descriptor corresponding to an input channel.
<<
val descr_of_out_channel : out_channel -> file_descr
>>
Return the descriptor corresponding to an output channel.
Seeking and truncating
=======================
<<
type seek_command =
SEEK_SET
| SEEK_CUR
| SEEK_END
>>
Positioning modes for `lseek'. `SEEK_SET' indicates positions
relative to the beginning of the file, `SEEK_CUR' relative to
the current position, `SEEK_END' relative to the end of the
file.
<<
val lseek : file_descr -> int -> mode:seek_command -> int
>>
Set the current position for a file descriptor
<<
val truncate : string -> len:int -> unit
>>
Truncates the named file to the given size.
<<
val ftruncate : file_descr -> len:int -> unit
>>
Truncates the file corresponding to the given descriptor to the
given size.
File statistics
================
<<
type file_kind =
S_REG (* Regular file *)
| S_DIR (* Directory *)
| S_CHR (* Character device *)
| S_BLK (* Block device *)
| S_LNK (* Symbolic link *)
| S_FIFO (* Named pipe *)
| S_SOCK (* Socket *)
type stats =
{ st_dev : int; (* Device number *)
st_ino : int; (* Inode number *)
st_kind : file_kind; (* Kind of the file *)
st_perm : file_perm; (* Access rights *)
st_nlink : int; (* Number of links *)
st_uid : int; (* User id of the owner *)
st_gid : int; (* Group ID of the file's group *)
st_rdev : int; (* Device minor number *)
st_size : int; (* Size in bytes *)
st_atime : float; (* Last access time *)
st_mtime : float; (* Last modification time *)
st_ctime : float } (* Last status change time *)
>>
The informations returned by the `stat' calls.
<<
val stat : string -> stats
>>
Return the information for the named file.
<<
val lstat : string -> stats
>>
Same as `stat', but in case the file is a symbolic link, return
the information for the link itself.
<<
val fstat : file_descr -> stats
>>
Return the information for the file associated with the given
descriptor.
Operations on file names
=========================
<<
val unlink : string -> unit
>>
Removes the named file
<<
val rename : src:string -> dst:string -> unit
>>
`rename old new' changes the name of a file from `old' to
`new'.
<<
val link : src:string -> dst:string -> unit
>>
`link source dest' creates a hard link named `dest' to the file
named `new'.
File permissions and ownership
===============================
<<
type access_permission =
R_OK (* Read permission *)
| W_OK (* Write permission *)
| X_OK (* Execution permission *)
| F_OK (* File exists *)
>>
Flags for the `access' call.
<<
val chmod : string -> perm:file_perm -> unit
>>
Change the permissions of the named file.
<<
val fchmod : file_descr -> perm:file_perm -> unit
>>
Change the permissions of an opened file.
<<
val chown : string -> uid:int -> gid:int -> unit
>>
Change the owner uid and owner gid of the named file.
<<
val fchown : file_descr -> uid:int -> gid:int -> unit
>>
Change the owner uid and owner gid of an opened file.
<<
val umask : int -> int
>>
Set the process creation mask, and return the previous mask.
<<
val access : string -> perm:access_permission list -> unit
>>
Check that the process has the given permissions over the named
file. Raise `Unix_error' otherwise.
Operations on file descriptors
===============================
<<
val dup : file_descr -> file_descr
>>
Return a new file descriptor referencing the same file as the
given descriptor.
<<
val dup2 : src:file_descr -> dst:file_descr -> unit
>>
`dup2 fd1 fd2' duplicates `fd1' to `fd2', closing `fd2' if
already opened.
<<
val set_nonblock : file_descr -> unit
val clear_nonblock : file_descr -> unit
>>
Set or clear the ``non-blocking'' flag on the given descriptor.
When the non-blocking flag is set, reading on a descriptor on
which there is temporarily no data available raises the `EAGAIN'
or `EWOULDBLOCK' error instead of blocking; writing on a
descriptor on which there is temporarily no room for writing
also raises `EAGAIN' or `EWOULDBLOCK'.
<<
val set_close_on_exec : file_descr -> unit
val clear_close_on_exec : file_descr -> unit
>>
Set or clear the ``close-on-exec'' flag on the given
descriptor. A descriptor with the close-on-exec flag is
automatically closed when the current process starts another
program with one of the `exec' functions.
Directories
============
<<
val mkdir : string -> perm:file_perm -> unit
>>
Create a directory with the given permissions.
<<
val rmdir : string -> unit
>>
Remove an empty directory.
<<
val chdir : string -> unit
>>
Change the process working directory.
<<
val getcwd : unit -> string
>>
Return the name of the current working directory.
<<
val chroot : string -> unit
>>
Change the process root directory.
<<
type dir_handle
>>
The type of descriptors over opened directories.
<<
val opendir : string -> dir_handle
>>
Open a descriptor on a directory
<<
val readdir : dir_handle -> string
>>
Return the next entry in a directory. Raise `End_of_file' when
the end of the directory has been reached.
<<
val rewinddir : dir_handle -> unit
>>
Reposition the descriptor to the beginning of the directory
<<
val closedir : dir_handle -> unit
>>
Close a directory descriptor.
Pipes and redirections
=======================
<<
val pipe : unit -> file_descr * file_descr
>>
Create a pipe. The first component of the result is opened for
reading, that's the exit to the pipe. The second component is
opened for writing, that's the entrance to the pipe.
<<
val mkfifo : string -> perm:file_perm -> unit
>>
Create a named pipe with the given permissions.
High-level process and redirection management
==============================================
<<
val create_process :
prog:string -> args:string array ->
stdin:file_descr -> stdout:file_descr -> stderr:file_descr -> int
>>
`create_process prog args new_stdin new_stdout new_stderr'
forks a new process that executes the program in file `prog',
with arguments `args'. The pid of the new process is returned
immediately; the new process executes concurrently with the
current process. The standard input and outputs of the new
process are connected to the descriptors `new_stdin',
`new_stdout' and `new_stderr'. Passing e.g. `stdout' for
`new_stdout' prevents the redirection and causes the new process
to have the same standard output as the current process. The
executable file `prog' is searched in the path. The new process
has the same environment as the current process. All file
descriptors of the current process are closed in the new
process, except those redirected to standard input and outputs.
<<
val create_process_env :
prog:string -> args:string array -> env:string array ->
stdin:file_descr -> stdout:file_descr -> stderr:file_descr -> int
>>
`create_process_env prog args env new_stdin new_stdout
new_stderr' works as `create_process', except that the extra
argument `env' specifies the environment passed to the program.
<<
val open_process_in: string -> in_channel
val open_process_out: string -> out_channel
val open_process: string -> in_channel * out_channel
>>
High-level pipe and process management. These functions run the
given command in parallel with the program, and return channels
connected to the standard input and/or the standard output of
the command. The command is interpreted by the shell `/bin/sh'
(cf. `system'). Warning: writes on channels are buffered, hence
be careful to call `flush' at the right times to ensure correct
synchronization.
<<
val open_process_full:
string -> env:string array -> in_channel * out_channel * in_channel
>>
Similar to `open_process', but the second argument specifies
the environment passed to the command. The result is a triple of
channels connected to the standard output, standard input, and
standard error of the command.
<<
val close_process_in: in_channel -> process_status
val close_process_out: out_channel -> process_status
val close_process: in_channel * out_channel -> process_status
val close_process_full: in_channel * out_channel * in_channel ->
process_status
>>
Close channels opened by `open_process_in', `open_process_out',
`open_process' and `open_process_full', respectively, wait for
the associated command to terminate, and return its termination
status.
Symbolic links
===============
<<
val symlink : src:string -> dst:string -> unit
>>
`symlink source dest' creates the file `dest' as a symbolic
link to the file `source'.
<<
val readlink : string -> string
>>
Read the contents of a link.
Polling
========
<<
val select :
read:file_descr list -> write:file_descr list -> except:file_descr list ->
timeout:float ->
file_descr list * file_descr list * file_descr list
>>
Wait until some input/output operations become possible on some
channels. The three list arguments are, respectively, a set of
descriptors to check for reading (first argument), for writing
(second argument), or for exceptional conditions (third
argument). The fourth argument is the maximal timeout, in
seconds; a negative fourth argument means no timeout (unbounded
wait). The result is composed of three sets of descriptors:
those ready for reading (first component), ready for writing
(second component), and over which an exceptional condition is
pending (third component).
Locking
========
<<
type lock_command =
F_ULOCK (* Unlock a region *)
| F_LOCK (* Lock a region for writing, and block if already locked
*)
| F_TLOCK (* Lock a region for writing, or fail if already locked *)
| F_TEST (* Test a region for other process locks *)
| F_RLOCK (* Lock a region for reading, and block if already locked
*)
| F_TRLOCK (* Lock a region for reading, or fail if already locked *)
>>
Commands for `lockf'.
<<
val lockf : file_descr -> mode:lock_command -> len:int -> unit
>>
`lockf fd cmd size' puts a lock on a region of the file opened
as `fd'. The region starts at the current read/write position
for `fd' (as set by `lseek'), and extends `size' bytes forward
if `size' is positive, `size' bytes backwards if `size' is
negative, or to the end of the file if `size' is zero. A write
lock (set with `F_LOCK' or `F_TLOCK') prevents any other process
from acquiring a read or write lock on the region. A read lock
(set with `F_RLOCK' or `F_TRLOCK') prevents any other process
from acquiring a write lock on the region, but lets other
processes acquire read locks on it.
Signals
========
<<
val kill : pid:int -> signal:int -> unit
>>
`kill pid sig' sends signal number `sig' to the process with id
`pid'.
<<
type sigprocmask_command = SIG_SETMASK | SIG_BLOCK | SIG_UNBLOCK
val sigprocmask: mode:sigprocmask_command -> int list -> int list
>>
`sigprocmask cmd sigs' changes the set of blocked signals. If
`cmd' is `SIG_SETMASK', blocked signals are set to those in the
list `sigs'. If `cmd' is `SIG_BLOCK', the signals in `sigs' are
added to the set of blocked signals. If `cmd' is `SIG_UNBLOCK',
the signals in `sigs' are removed from the set of blocked
signals. `sigprocmask' returns the set of previously blocked
signals.
<<
val sigpending: unit -> int list
>>
Return the set of blocked signals that are currently pending.
<<
val sigsuspend: int list -> unit
>>
`sigsuspend sigs' atomically sets the blocked signals to `sig'
and waits for a non-ignored, non-blocked signal to be delivered.
On return, the blocked signals are reset to their initial value.
<<
val pause : unit -> unit
>>
Wait until a non-ignored, non-blocked signal is delivered.
Time functions
===============
<<
type process_times =
{ tms_utime : float; (* User time for the process *)
tms_stime : float; (* System time for the process *)
tms_cutime : float; (* User time for the children processes *)
tms_cstime : float } (* System time for the children processes *)
>>
The execution times (CPU times) of a process.
<<
type tm =
{ tm_sec : int; (* Seconds 0..59 *)
tm_min : int; (* Minutes 0..59 *)
tm_hour : int; (* Hours 0..23 *)
tm_mday : int; (* Day of month 1..31 *)
tm_mon : int; (* Month of year 0..11 *)
tm_year : int; (* Year - 1900 *)
tm_wday : int; (* Day of week (Sunday is 0) *)
tm_yday : int; (* Day of year 0..365 *)
tm_isdst : bool } (* Daylight time savings in effect *)
>>
The type representing wallclock time and calendar date.
<<
val time : unit -> float
>>
Return the current time since 00:00:00 GMT, Jan. 1, 1970, in
seconds.
<<
val gettimeofday : unit -> float
>>
Same as `time', but with resolution better than 1 second.
<<
val gmtime : float -> tm
>>
Convert a time in seconds, as returned by `time', into a date
and a time. Assumes Greenwich meridian time zone, also known as
UTC.
<<
val localtime : float -> tm
>>
Convert a time in seconds, as returned by `time', into a date
and a time. Assumes the local time zone.
<<
val mktime : tm -> float * tm
>>
Convert a date and time, specified by the `tm' argument, into a
time in seconds, as returned by `time'. Also return a normalized
copy of the given `tm' record, with the `tm_wday', `tm_yday',
and `tm_isdst' fields recomputed from the other fields. The `tm'
argument is interpreted in the local time zone.
<<
val alarm : int -> int
>>
Schedule a `SIGALRM' signals after the given number of seconds.
<<
val sleep : int -> unit
>>
Stop execution for the given number of seconds.
<<
val times : unit -> process_times
>>
Return the execution times of the process.
<<
val utimes : string -> access:float -> modif:float -> unit
>>
Set the last access time (second arg) and last modification
time (third arg) for a file. Times are expressed in seconds from
00:00:00 GMT, Jan. 1, 1970.
<<
type interval_timer =
ITIMER_REAL
| ITIMER_VIRTUAL
| ITIMER_PROF
>>
The three kinds of interval timers. `ITIMER_REAL' decrements in
real time, and sends the signal `SIGALRM' when expired.
`ITIMER_VIRTUAL' decrements in process virtual time, and sends
`SIGVTALRM' when expired. `ITIMER_PROF' (for profiling)
decrements both when the process is running and when the system
is running on behalf of the process; it sends `SIGPROF' when
expired.
<<
type interval_timer_status =
{ it_interval: float; (* Period *)
it_value: float } (* Current value of the timer *)
>>
The type describing the status of an interval timer
<<
val getitimer: interval_timer -> interval_timer_status
>>
Return the current status of the given interval timer.
<<
val setitimer:
interval_timer -> interval_timer_status -> interval_timer_status
>>
`setitimer t s' sets the interval timer `t' and returns its
previous status. The `s' argument is interpreted as follows:
`s.it_value', if nonzero, is the time to the next timer
expiration; `s.it_interval', if nonzero, specifies a value to be
used in reloading it_value when the timer expires. Setting
`s.it_value' to zero disable the timer. Setting `s.it_interval'
to zero causes the timer to be disabled after its next
expiration.
User id, group id
==================
<<
val getuid : unit -> int
>>
Return the user id of the user executing the process.
<<
val geteuid : unit -> int
>>
Return the effective user id under which the process runs.
<<
val setuid : int -> unit
>>
Set the real user id and effective user id for the process.
<<
val getgid : unit -> int
>>
Return the group id of the user executing the process.
<<
val getegid : unit -> int
>>
Return the effective group id under which the process runs.
<<
val setgid : int -> unit
>>
Set the real group id and effective group id for the process.
<<
val getgroups : unit -> int array
>>
Return the list of groups to which the user executing the
process belongs.
<<
type passwd_entry =
{ pw_name : string;
pw_passwd : string;
pw_uid : int;
pw_gid : int;
pw_gecos : string;
pw_dir : string;
pw_shell : string }
>>
Structure of entries in the `passwd' database.
<<
type group_entry =
{ gr_name : string;
gr_passwd : string;
gr_gid : int;
gr_mem : string array }
>>
Structure of entries in the `groups' database.
<<
val getlogin : unit -> string
>>
Return the login name of the user executing the process.
<<
val getpwnam : string -> passwd_entry
>>
Find an entry in `passwd' with the given name, or raise
`Not_found'.
<<
val getgrnam : string -> group_entry
>>
Find an entry in `group' with the given name, or raise
`Not_found'.
<<
val getpwuid : int -> passwd_entry
>>
Find an entry in `passwd' with the given user id, or raise
`Not_found'.
<<
val getgrgid : int -> group_entry
>>
Find an entry in `group' with the given group id, or raise
`Not_found'.
Internet addresses
===================
<<
type inet_addr
>>
The abstract type of Internet addresses.
<<
val inet_addr_of_string : string -> inet_addr
val string_of_inet_addr : inet_addr -> string
>>
Conversions between string with the format `XXX.YYY.ZZZ.TTT'
and Internet addresses. `inet_addr_of_string' raises `Failure'
when given a string that does not match this format.
<<
val inet_addr_any : inet_addr
>>
A special Internet address, for use only with `bind',
representing all the Internet addresses that the host machine
possesses.
Sockets
========
<<
type socket_domain =
PF_UNIX (* Unix domain *)
| PF_INET (* Internet domain *)
>>
The type of socket domains.
<<
type socket_type =
SOCK_STREAM (* Stream socket *)
| SOCK_DGRAM (* Datagram socket *)
| SOCK_RAW (* Raw socket *)
| SOCK_SEQPACKET (* Sequenced packets socket *)
>>
The type of socket kinds, specifying the semantics of
communications.
<<
type sockaddr =
ADDR_UNIX of string
| ADDR_INET of inet_addr * int
>>
The type of socket addresses. `ADDR_UNIX name' is a socket
address in the Unix domain; `name' is a file name in the file
system. `ADDR_INET(addr,port)' is a socket address in the
Internet domain; `addr' is the Internet address of the machine,
and `port' is the port number.
<<
val socket :
domain:socket_domain -> kind:socket_type -> protocol:int -> file_descr
>>
Create a new socket in the given domain, and with the given
kind. The third argument is the protocol type; 0 selects the
default protocol for that kind of sockets.
<<
val socketpair :
domain:socket_domain -> kind:socket_type -> protocol:int ->
file_descr * file_descr
>>
Create a pair of unnamed sockets, connected together.
<<
val accept : file_descr -> file_descr * sockaddr
>>
Accept connections on the given socket. The returned descriptor
is a socket connected to the client; the returned address is the
address of the connecting client.
<<
val bind : file_descr -> addr:sockaddr -> unit
>>
Bind a socket to an address.
<<
val connect : file_descr -> addr:sockaddr -> unit
>>
Connect a socket to an address.
<<
val listen : file_descr -> max:int -> unit
>>
Set up a socket for receiving connection requests. The integer
argument is the maximal number of pending requests.
<<
type shutdown_command =
SHUTDOWN_RECEIVE (* Close for receiving *)
| SHUTDOWN_SEND (* Close for sending *)
| SHUTDOWN_ALL (* Close both *)
>>
The type of commands for `shutdown'.
<<
val shutdown : file_descr -> mode:shutdown_command -> unit
>>
Shutdown a socket connection. `SHUTDOWN_SEND' as second
argument causes reads on the other end of the connection to
return an end-of-file condition. `SHUTDOWN_RECEIVE' causes
writes on the other end of the connection to return a closed
pipe condition (`SIGPIPE' signal).
<<
val getsockname : file_descr -> sockaddr
>>
Return the address of the given socket.
<<
val getpeername : file_descr -> sockaddr
>>
Return the address of the host connected to the given socket.
<<
type msg_flag =
MSG_OOB
| MSG_DONTROUTE
| MSG_PEEK
>>
The flags for `recv', `recvfrom', `send' and `sendto'.
<<
val recv :
file_descr -> buf:string -> pos:int -> len:int
-> mode:msg_flag list -> int
val recvfrom :
file_descr -> buf:string -> pos:int -> len:int
-> mode:msg_flag list -> int * sockaddr
>>
Receive data from an unconnected socket.
<<
val send : file_descr -> buf:string -> pos:int -> len:int
-> mode:msg_flag list -> int
val sendto :
file_descr -> buf:string -> pos:int -> len:int
-> mode:msg_flag list -> addr:sockaddr -> int
>>
Send data over an unconnected socket.
<<
type socket_option =
SO_DEBUG (* Record debugging information *)
| SO_BROADCAST (* Permit sending of broadcast messages *)
| SO_REUSEADDR (* Allow reuse of local addresses for bind *)
| SO_KEEPALIVE (* Keep connection active *)
| SO_DONTROUTE (* Bypass the standard routing algorithms *)
| SO_OOBINLINE (* Leave out-of-band data in line *)
>>
The socket options settable with `setsockopt'.
<<
val getsockopt : file_descr -> socket_option -> bool
>>
Return the current status of an option in the given socket.
<<
val setsockopt : file_descr -> socket_option -> bool -> unit
>>
Set or clear an option in the given socket.
High-level network connection functions
========================================
<<
val open_connection : sockaddr -> in_channel * out_channel
>>
Connect to a server at the given address. Return a pair of
buffered channels connected to the server. Remember to call
`flush' on the output channel at the right times to ensure
correct synchronization.
<<
val shutdown_connection : in_channel -> unit
>>
``Shut down'' a connection established with `open_connection';
that is, transmit an end-of-file condition to the server reading
on the other side of the connection.
<<
val establish_server : (in_channel -> out_channel -> unit) ->
addr:sockaddr -> unit
>>
Establish a server on the given address. The function given as
first argument is called for each connection with two buffered
channels connected to the client. A new process is created for
each connection. The function `establish_server' never returns
normally.
Host and protocol databases
============================
<<
type host_entry =
{ h_name : string;
h_aliases : string array;
h_addrtype : socket_domain;
h_addr_list : inet_addr array }
>>
Structure of entries in the `hosts' database.
<<
type protocol_entry =
{ p_name : string;
p_aliases : string array;
p_proto : int }
>>
Structure of entries in the `protocols' database.
<<
type service_entry =
{ s_name : string;
s_aliases : string array;
s_port : int;
s_proto : string }
>>
Structure of entries in the `services' database.
<<
val gethostname : unit -> string
>>
Return the name of the local host.
<<
val gethostbyname : string -> host_entry
>>
Find an entry in `hosts' with the given name, or raise
`Not_found'.
<<
val gethostbyaddr : inet_addr -> host_entry
>>
Find an entry in `hosts' with the given address, or raise
`Not_found'.
<<
val getprotobyname : string -> protocol_entry
>>
Find an entry in `protocols' with the given name, or raise
`Not_found'.
<<
val getprotobynumber : int -> protocol_entry
>>
Find an entry in `protocols' with the given protocol number, or
raise `Not_found'.
<<
val getservbyname : string -> protocol:string -> service_entry
>>
Find an entry in `services' with the given name, or raise
`Not_found'.
<<
val getservbyport : int -> protocol:string -> service_entry
>>
Find an entry in `services' with the given service number, or
raise `Not_found'.
Terminal interface
===================
The following functions implement the POSIX standard terminal
interface. They provide control over asynchronous communication
ports and pseudo-terminals. Refer to the `termios' man page for
a complete description.
<<
type terminal_io = {
>>
Input modes:
<<
mutable c_ignbrk: bool; (* Ignore the break condition. *)
mutable c_brkint: bool; (* Signal interrupt on break condition. *)
mutable c_ignpar: bool; (* Ignore characters with parity errors. *)
mutable c_parmrk: bool; (* Mark parity errors. *)
mutable c_inpck: bool; (* Enable parity check on input. *)
mutable c_istrip: bool; (* Strip 8th bit on input characters. *)
mutable c_inlcr: bool; (* Map NL to CR on input. *)
mutable c_igncr: bool; (* Ignore CR on input. *)
mutable c_icrnl: bool; (* Map CR to NL on input. *)
mutable c_ixon: bool; (* Recognize XON/XOFF characters on input. *)
mutable c_ixoff: bool; (* Emit XON/XOFF chars to control input flow. *)
>>
Output modes:
<<
mutable c_opost: bool; (* Enable output processing. *)
>>
Control modes:
<<
mutable c_obaud: int; (* Output baud rate (0 means close
connection).*)
mutable c_ibaud: int; (* Input baud rate. *)
mutable c_csize: int; (* Number of bits per character (5-8). *)
mutable c_cstopb: int; (* Number of stop bits (1-2). *)
mutable c_cread: bool; (* Reception is enabled. *)
mutable c_parenb: bool; (* Enable parity generation and detection. *)
mutable c_parodd: bool; (* Specify odd parity instead of even. *)
mutable c_hupcl: bool; (* Hang up on last close. *)
mutable c_clocal: bool; (* Ignore modem status lines. *)
>>
Local modes:
<<
mutable c_isig: bool; (* Generate signal on INTR, QUIT, SUSP. *)
mutable c_icanon: bool; (* Enable canonical processing
(line buffering and editing) *)
mutable c_noflsh: bool; (* Disable flush after INTR, QUIT, SUSP. *)
mutable c_echo: bool; (* Echo input characters. *)
mutable c_echoe: bool; (* Echo ERASE (to erase previous character). *)
mutable c_echok: bool; (* Echo KILL (to erase the current line). *)
mutable c_echonl: bool; (* Echo NL even if c_echo is not set. *)
>>
Control characters:
<<
mutable c_vintr: char; (* Interrupt character (usually ctrl-C). *)
mutable c_vquit: char; (* Quit character (usually ctrl-\). *)
mutable c_verase: char; (* Erase character (usually DEL or ctrl-H). *)
mutable c_vkill: char; (* Kill line character (usually ctrl-U). *)
mutable c_veof: char; (* End-of-file character (usually ctrl-D). *)
mutable c_veol: char; (* Alternate end-of-line char. (usually none).
*)
mutable c_vmin: int; (* Minimum number of characters to read
before the read request is satisfied. *)
mutable c_vtime: int; (* Maximum read wait (in 0.1s units). *)
mutable c_vstart: char; (* Start character (usually ctrl-Q). *)
mutable c_vstop: char (* Stop character (usually ctrl-S). *)
}
val tcgetattr: file_descr -> terminal_io
>>
Return the status of the terminal referred to by the given file
descriptor.
<<
type setattr_when = TCSANOW | TCSADRAIN | TCSAFLUSH
val tcsetattr: file_descr -> mode:setattr_when -> terminal_io -> unit
>>
Set the status of the terminal referred to by the given file
descriptor. The second argument indicates when the status change
takes place: immediately (`TCSANOW'), when all pending output
has been transmitted (`TCSADRAIN'), or after flushing all input
that has been received but not read (`TCSAFLUSH'). `TCSADRAIN'
is recommended when changing the output parameters; `TCSAFLUSH',
when changing the input parameters.
<<
val tcsendbreak: file_descr -> duration:int -> unit
>>
Send a break condition on the given file descriptor. The second
argument is the duration of the break, in 0.1s units; 0 means
standard duration (0.25s).
<<
val tcdrain: file_descr -> unit
>>
Waits until all output written on the given file descriptor has
been transmitted.
<<
type flush_queue = TCIFLUSH | TCOFLUSH | TCIOFLUSH
val tcflush: file_descr -> mode:flush_queue -> unit
>>
Discard data written on the given file descriptor but not yet
transmitted, or data received but not yet read, depending on the
second argument: `TCIFLUSH' flushes data received but not read,
`TCOFLUSH' flushes data written but not transmitted, and
`TCIOFLUSH' flushes both.
<<
type flow_action = TCOOFF | TCOON | TCIOFF | TCION
val tcflow: file_descr -> mode:flow_action -> unit
>>
Suspend or restart reception or transmission of data on the
given file descriptor, depending on the second argument:
`TCOOFF' suspends output, `TCOON' restarts output, `TCIOFF'
transmits a STOP character to suspend input, and `TCION'
transmits a START character to restart input.
<<
val setsid : unit -> int
>>
Put the calling process in a new session and detach it from its
controlling terminal.
MacOS:
Under MacOS, the Unix library is only available in the toplevel
application, not in MPW tools. Below is a list of the functions
that are not implemented, or only partially implemented, under
MacOS. Functions not mentioned are fully implemented and behave
as described previously in this chapter.
----------------------------------------------------------
| Functions | Comment |
----------------------------------------------------------
|chown, fchown |not implemented |
|chroot |not implemented |
|environment, putenv |not implemented |
|execv, execve, execvp, execvpe |not implemented |
|fork |not implemented, use |
| |threads |
|getegid, geteuid, getgid, getuid|always return 1 |
|getgrnam, getgrgid |not implemented |
|getlogin |returns the user name |
| |as set in the Internet |
| |control panel |
|getpid |returns the low-order |
| |31 bits of the PSN |
|getppid |not implemented |
|getpwnam, getpwuid |not implemented |
|kill |not implemented |
|link |not implemented |
|mkfifo |not implemented |
|nice |not implemented |
|setgid, setuid |not implemented |
|times |only the process user |
| |time is returned |
|umask |not implemented |
|wait |not implemented |
|waitpid |not implemented |
|establish_server |not implemented; use |
| |threads |
|terminal functions (tc*) |not implemented |
----------------------------------------------------------
Windows:
The Cygwin port of Objective Caml fully implements all
functions from the Unix module. The native Win32 port implements
a subset of them. Below is a list of the functions that are not
implemented, or only partially implemented, by the Win32 port.
Functions not mentioned are fully implemented and behave as
described previously in this chapter.
------------------------------------------------------
| Functions | Comment |
------------------------------------------------------
|fork |not implemented, use |
| |create_process or |
| |threads |
|wait |not implemented, use |
| |waitpid |
|waitpid |can only wait for a |
| |given PID, not any |
| |child process |
|getppid |not implemented |
| |(meaningless under |
| |Windows) |
|nice |not implemented |
|in_channel_of_descr |does not work on |
| |sockets under Windows |
| |95, 98, ME; works fine |
| |under NT and 2000 |
|out_channel_of_descr |ditto |
|truncate, ftruncate |not implemented |
|lstat, fstat |not implemented |
|link, symlink, readlink |not implemented (no |
| |links under Windows) |
|fchmod |not implemented |
|chown, fchown |not implemented (make |
| |no sense on a DOS file |
| |system) |
|umask |not implemented |
|set_nonblock, clear_nonblock|implemented as dummy |
| |functions; use threads |
| |instead of non-blocking|
| |I/O |
|rewinddir |not implemented; |
| |re-open the directory |
| |instead |
|mkfifo |not implemented |
|select |implemented, but works |
| |only for sockets; use |
| |threads if you need to|
| |wait on other kinds of |
| |file descriptors |
|lockf |not implemented |
|kill, pause |not implemented (no |
| |inter-process signals |
| |in Windows) |
|alarm, times |not implemented |
|getitimer, setitimer |not implemented |
|getuid, getgid |always return 1 |
|getgid, getegid, getgroups |not implemented |
|setuid, setgid |not implemented |
|getpwnam, getpwuid |always raise Not_found |
|getgrnam, getgrgid |always raise Not_found |
|type socket_domain |the domain PF_UNIX is |
| |not supported; PF_INET |
| |is fully supported |
|establish_server |not implemented; use |
| |threads |
|terminal functions (tc*) |not implemented |
------------------------------------------------------
Chapter 21 The num library: arbitrary-precision rational arithmetic
***********************************************************************
The num library implements exact-precision rational arithmetic. It is built
upon the BigNum arbitrary-precision integer arithmetic package, and therefore
achieves fairly high performance.
The functions provided in this library are fully documented in The CAML
Numbers Reference Manual by Valérie Ménissier-Morain, technical report 141,
INRIA, july 1992 (available electronically,
ftp://ftp.inria.fr/INRIA/publication/RT/RT-0141.ps.gz). A summary of the
functions is given below.
Programs that use the num library must be linked as follows:
<<
ocamlc other options nums.cma other files
ocamlopt other options nums.cmxa other files
>>
For interactive use of the nums library, do:
<<
ocamlmktop -o mytop nums.cma
./mytop
>>
21.1 Module Num: operation on arbitrary-precision numbers
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
<<
open Nat
open Big_int
open Ratio
>>
Numbers (type `num') are arbitrary-precision rational numbers,
plus the special elements `1/0' (infinity) and `0/0'
(undefined).
<<
type num = Int of int | Big_int of big_int | Ratio of ratio
>>
The type of numbers.
Arithmetic operations
<<
val (+/) : num -> num -> num
val add_num : num -> num -> num
>>
Addition
<<
val minus_num : num -> num
>>
Unary negation.
<<
val (-/) : num -> num -> num
val sub_num : num -> num -> num
>>
Subtraction
<<
val (*/) : num -> num -> num
val mult_num : num -> num -> num
>>
Multiplication
<<
val square_num : num -> num
>>
Squaring
<<
val (//) : num -> num -> num
val div_num : num -> num -> num
>>
Division
<<
val quo_num : num -> num -> num
val mod_num : num -> num -> num
>>
Euclidean division: quotient and remainder
<<
val (**/) : num -> num -> num
val power_num : num -> num -> num
>>
Exponentiation
<<
val is_integer_num : num -> bool
>>
Test if a number is an integer
<<
val integer_num : num -> num
val floor_num : num -> num
val round_num : num -> num
val ceiling_num : num -> num
>>
Approximate a number by an integer. `floor_num n' returns the
largest integer smaller or equal to `n'. `ceiling_num n' returns
the smallest integer bigger or equal to `n'. `integer_num n'
returns the integer closest to `n'. In case of ties, rounds
towards zero. `round_num n' returns the integer closest to `n'.
In case of ties, rounds off zero.
<<
val sign_num : num -> int
>>
Return `-1', `0' or `1' according to the sign of the argument.
<<
val (=/) : num -> num -> bool
val (</) : num -> num -> bool
val (>/) : num -> num -> bool
val (<=/) : num -> num -> bool
val (>=/) : num -> num -> bool
val (<>/) : num -> num -> bool
val eq_num : num -> num -> bool
val lt_num : num -> num -> bool
val le_num : num -> num -> bool
val gt_num : num -> num -> bool
val ge_num : num -> num -> bool
>>
Usual comparisons between numbers
<<
val compare_num : num -> num -> int
>>
Return `-1', `0' or `1' if the first argument is less than,
equal to, or greater than the second argument.
<<
val max_num : num -> num -> num
val min_num : num -> num -> num
>>
Return the greater (resp. the smaller) of the two arguments.
<<
val abs_num : num -> num
>>
Absolute value.
<<
val succ_num: num -> num
>>
`succ n' is `n+1'
<<
val pred_num: num -> num
>>
`pred n' is `n-1'
<<
val incr_num: num ref -> unit
>>
`incr r' is `r:=!r+1', where `r' is a reference to a number.
<<
val decr_num: num ref -> unit
>>
`decr r' is `r:=!r-1', where `r' is a reference to a number.
Coercions with strings
<<
val string_of_num : num -> string
>>
Convert a number to a string, using fractional notation.
<<
val approx_num_fix : int -> num -> string
val approx_num_exp : int -> num -> string
>>
Approximate a number by a decimal. The first argument is the
required precision. The second argument is the number to
approximate. `approx_fix' uses decimal notation; the first
argument is the number of digits after the decimal point.
`approx_exp' uses scientific (exponential) notation; the first
argument is the number of digits in the mantissa.
<<
val num_of_string : string -> num
>>
Convert a string to a number.
Coercions between numerical types
<<
val int_of_num : num -> int
val num_of_int : int -> num
val nat_of_num : num -> nat
val num_of_nat : nat -> num
val num_of_big_int : big_int -> num
val big_int_of_num : num -> big_int
val ratio_of_num : num -> ratio
val num_of_ratio : ratio -> num
val float_of_num : num -> float
>>
21.2 Module Arith_status: flags that control rational arithmetic
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
val arith_status: unit -> unit
>>
Print the current status of the arithmetic flags.
<<
val get_error_when_null_denominator : unit -> bool
val set_error_when_null_denominator : bool -> unit
>>
Get or set the flag `null_denominator'. When on, attempting to
create a rational with a null denominator raises an exception.
When off, rationals with null denominators are accepted.
Initially: on.
<<
val get_normalize_ratio : unit -> bool
val set_normalize_ratio : bool -> unit
>>
Get or set the flag `normalize_ratio'. When on, rational
numbers are normalized after each operation. When off, rational
numbers are not normalized until printed. Initially: off.
<<
val get_normalize_ratio_when_printing : unit -> bool
val set_normalize_ratio_when_printing : bool -> unit
>>
Get or set the flag `normalize_ratio_when_printing'. When on,
rational numbers are normalized before being printed. When off,
rational numbers are printed as is, without normalization.
Initially: on.
<<
val get_approx_printing : unit -> bool
val set_approx_printing : bool -> unit
>>
Get or set the flag `approx_printing'. When on, rational
numbers are printed as a decimal approximation. When off,
rational numbers are printed as a fraction. Initially: off.
<<
val get_floating_precision : unit -> int
val set_floating_precision : int -> unit
>>
Get or set the parameter `floating_precision'. This parameter
is the number of digits displayed when `approx_printing' is on.
Initially: 12.
Chapter 22 The str library: regular expressions and string processing
*************************************************************************
The str library provides high-level string processing functions, some based
on regular expressions. It is intended to support the kind of file processing
that is usually performed with scripting languages such as awk, perl or sed.
Programs that use the str library must be linked as follows:
<<
ocamlc other options str.cma other files
ocamlopt other options str.cmxa other files
>>
For interactive use of the str library, do:
<<
ocamlmktop -o mytop str.cma
./mytop
>>
22.1 Module Str: regular expressions and high-level string processing
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
Regular expressions
====================
<<
type regexp
>>
The type of compiled regular expressions.
<<
val regexp: string -> regexp
>>
Compile a regular expression. The syntax for regular
expressions is the same as in Gnu Emacs. The special characters
are `$^.*+?[]'. The following constructs are recognized:
`. ' matches any character except newline
`* ' (postfix) matches the previous expression zero, one or
several times
`+ ' (postfix) matches the previous expression one or
several times
`? ' (postfix) matches the previous expression once or not
at all
`[..] ' character set; ranges are denoted with `-', as in
`[a-z]'; an initial `^', as in `[^0-9]', complements the set
`^ ' matches at beginning of line
`$ ' matches at end of line
`\| ' (infix) alternative between two expressions
`\(..\)' grouping and naming of the enclosed expression
`\1 ' the text matched by the first `\(...\)' expression
(`\2' for the second expression, etc)
`\b ' matches word boundaries
`\ ' quotes special characters.
<<
val regexp_case_fold: string -> regexp
>>
Same as `regexp', but the compiled expression will match text
in a case-insensitive way: uppercase and lowercase letters will
be considered equivalent.
<<
val quote: string -> string
>>
`Str.quote s' returns a regexp string that matches exactly `s'
and nothing else.
<<
val regexp_string: string -> regexp
val regexp_string_case_fold: string -> regexp
>>
`Str.regexp_string s' returns a regular expression that matches
exactly `s' and nothing else. `Str.regexp_string_case_fold' is
similar, but the regexp matches in a case-insensitive way.
String matching and searching
==============================
<<
val string_match: pat:regexp -> string -> pos:int -> bool
>>
`string_match r s start' tests whether the characters in `s'
starting at position `start' match the regular expression `r'.
The first character of a string has position `0', as usual.
<<
val search_forward: pat:regexp -> string -> pos:int -> int
>>
`search_forward r s start' searchs the string `s' for a
substring matching the regular expression `r'. The search starts
at position `start' and proceeds towards the end of the string.
Return the position of the first character of the matched
substring, or raise `Not_found' if no substring matches.
<<
val search_backward: pat:regexp -> string -> pos:int -> int
>>
Same as `search_forward', but the search proceeds towards the
beginning of the string.
<<
val string_partial_match: pat:regexp -> string -> pos:int -> bool
>>
Similar to `string_match', but succeeds whenever the argument
string is a prefix of a string that matches. This includes the
case of a true complete match.
<<
val matched_string: string -> string
>>
`matched_string s' returns the substring of `s' that was
matched by the latest `string_match', `search_forward' or
`search_backward'. The user must make sure that the parameter
`s' is the same string that was passed to the matching or
searching function.
<<
val match_beginning: unit -> int
val match_end: unit -> int
>>
`match_beginning()' returns the position of the first character
of the substring that was matched by `string_match',
`search_forward' or `search_backward'. `match_end()' returns the
position of the character following the last character of the
matched substring.
<<
val matched_group: int -> string -> string
>>
`matched_group n s' returns the substring of `s' that was
matched by the `n'th group `\(...\)' of the regular expression
during the latest `string_match', `search_forward' or
`search_backward'. The user must make sure that the parameter
`s' is the same string that was passed to the matching or
searching function. `matched_group n s' raises `Not_found' if
the `n'th group of the regular expression was not matched. This
can happen with groups inside alternatives `\|', options `?' or
repetitions `*'. For instance, the empty string will match
`\(a\)*', but `matched_group 1 ""' will raise `Not_found'
because the first group itself was not matched.
<<
val group_beginning: int -> int
val group_end: int -> int
>>
`group_beginning n' returns the position of the first character
of the substring that was matched by the `n'th group of the
regular expression. `group_end n' returns the position of the
character following the last character of the matched substring.
Both functions raise `Not_found' if the `n'th group of the
regular expression was not matched.
Replacement
============
<<
val global_replace: pat:regexp -> templ:string -> string -> string
>>
`global_replace regexp templ s' returns a string identical to
`s', except that all substrings of `s' that match `regexp' have
been replaced by `templ'. The replacement template `templ' can
contain `\1', `\2', etc; these sequences will be replaced by the
text matched by the corresponding group in the regular
expression. `\0' stands for the text matched by the whole
regular expression.
<<
val replace_first: pat:regexp -> templ:string -> string -> string
>>
Same as `global_replace', except that only the first substring
matching the regular expression is replaced.
<<
val global_substitute:
pat:regexp -> subst:(string -> string) -> string -> string
>>
`global_substitute regexp subst s' returns a string identical
to `s', except that all substrings of `s' that match `regexp'
have been replaced by the result of function `subst'. The
function `subst' is called once for each matching substring, and
receives `s' (the whole text) as argument.
<<
val substitute_first:
pat:regexp -> subst:(string -> string) -> string -> string
>>
Same as `global_substitute', except that only the first
substring matching the regular expression is replaced.
<<
val replace_matched : templ:string -> string -> string
>>
`replace_matched repl s' returns the replacement text `repl' in
which `\1', `\2', etc. have been replaced by the text matched by
the corresponding groups in the most recent matching operation.
`s' must be the same string that was matched during this
matching operation.
Splitting
==========
<<
val split: sep:regexp -> string -> string list
>>
`split r s' splits `s' into substrings, taking as delimiters
the substrings that match `r', and returns the list of
substrings. For instance, `split (regexp "[ \t]+") s' splits `s'
into blank-separated words. An occurrence of the delimiter at
the beginning and at the end of the string is ignored.
<<
val bounded_split: sep:regexp -> string -> max:int -> string list
>>
Same as `split', but splits into at most `n' substrings, where
`n' is the extra integer parameter.
<<
val split_delim: sep:regexp -> string -> string list
val bounded_split_delim: sep:regexp -> string -> max:int -> string list
>>
Same as `split' and `bounded_split', but occurrences of the
delimiter at the beginning and at the end of the string are
recognized and returned as empty strings in the result. For
instance, `split_delim (regexp " ") " abc "' returns `["";
"abc"; ""]', while `split' with the same arguments returns
`["abc"]'.
<<
type split_result = Text of string | Delim of string
val full_split: sep:regexp -> string -> split_result list
val bounded_full_split: sep:regexp -> string -> int -> split_result list
>>
Same as `split_delim' and `bounded_split_delim', but returns
the delimiters as well as the substrings contained between
delimiters. The former are tagged `Delim' in the result list;
the latter are tagged `Text'. For instance, `full_split (regexp
"[{}]") "{ab}"' returns `[Delim "{"; Text "ab"; Delim "}"]'.
Extracting substrings
======================
<<
val string_before: string -> int -> string
>>
`string_before s n' returns the substring of all characters of
`s' that precede position `n' (excluding the character at
position `n').
<<
val string_after: string -> int -> string
>>
`string_after s n' returns the substring of all characters of
`s' that follow position `n' (including the character at
position `n').
<<
val first_chars: string -> len:int -> string
>>
`first_chars s n' returns the first `n' characters of `s'. This
is the same function as `string_before'.
<<
val last_chars: string -> len:int -> string
>>
`last_chars s n' returns the last `n' characters of `s'.
Chapter 23 The threads library
**********************************
The threads library allows concurrent programming in Objective Caml. It
provides multiple threads of control (also called lightweight processes) that
execute concurrently in the same memory space. Threads communicate by in-place
modification of shared data structures, or by sending and receiving data on
communication channels.
The threads library is implemented by time-sharing on a single processor. It
will not take advantage of multi-processor machines. Using this library will
therefore never make programs run faster. However, many programs are easier to
write when structured as several communicating processes.
Unix:
Programs that use the threads library must be linked as
follows:
<<
ocamlc -thread other options threads.cma other files
>>
The -thread option selects a special, thread-safe version of
the standard library (see chapter 8). The -thread option must
also be given when compiling any source file that references
modules from the thread library (Thread, Mutex, ...).
The default thread implementation cannot be used in native-code
programs compiled with ocamlopt. If your operating system
provides POSIX 1003.1c compliant threads, you can select an
alternate implementation when configuring Objective Caml (use
the -with-pthread option to configure) which also supports
native-code programs. Programs that use this alternate
implementation of the threads library must be linked as follows:
<<
ocamlc -thread other options threads.cma other files
ocamlopt -thread other options threads.cmxa other
files
>>
Depending on the operating system, extra system libraries can
be necessary. For instance, under Solaris 2.5, add -cclib
-lposix4 at the end of the command line.
Windows:
Programs that use the threads library must be linked as
follows:
<<
ocamlc -thread other options threads.cma other files
>>
All object files on the command line must also have been
compiled with the -thread option, which selects a special,
thread-safe version of the standard library (see chapter 8).
23.1 Module Thread: lightweight threads
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
<<
type t
>>
The type of thread handles.
Thread creation and termination
--------------------------------
<<
val create : ('a -> 'b) -> 'a -> t
>>
`Thread.create funct arg' creates a new thread of control, in
which the function application `funct arg' is executed
concurrently with the other threads of the program. The
application of `Thread.create' returns the handle of the newly
created thread. The new thread terminates when the application
`funct arg' returns, either normally or by raising an uncaught
exception. In the latter case, the exception is printed on
standard error, but not propagated back to the parent thread.
Similarly, the result of the application `funct arg' is
discarded and not directly accessible to the parent thread.
<<
val self : unit -> t
>>
Return the thread currently executing.
<<
val id : t -> int
>>
Return the identifier of the given thread. A thread identifier
is an integer that identifies uniquely the thread. It can be
used to build data structures indexed by threads.
<<
val exit : unit -> unit
>>
Terminate prematurely the currently executing thread.
<<
val kill : t -> unit
>>
Terminate prematurely the thread whose handle is given. This
functionality is available only with bytecode-level threads.
Suspending threads
-------------------
<<
val delay: float -> unit
>>
`delay d' suspends the execution of the calling thread for `d'
seconds. The other program threads continue to run during this
time.
<<
val join : t -> unit
>>
`join th' suspends the execution of the calling thread until
the thread `th' has terminated.
<<
val wait_read : Unix.file_descr -> unit
val wait_write : Unix.file_descr -> unit
>>
Suspend the execution of the calling thread until at least one
character is available for reading (`wait_read') or one
character can be written without blocking (`wait_write') on the
given Unix file descriptor.
<<
val wait_timed_read : Unix.file_descr -> timeout:float -> bool
val wait_timed_write : Unix.file_descr -> timeout:float -> bool
>>
Same as `wait_read' and `wait_write', but wait for at most the
amount of time given as second argument (in seconds). Return
`true' if the file descriptor is ready for input/output and
`false' if the timeout expired.
<<
val select :
read:Unix.file_descr list -> write:Unix.file_descr list ->
exn:Unix.file_descr list -> timeout:float ->
Unix.file_descr list * Unix.file_descr list * Unix.file_descr list
>>
Suspend the execution of the calling thead until input/output
becomes possible on the given Unix file descriptors. The
arguments and results have the same meaning as for
`Unix.select'.
<<
val wait_pid : int -> int * Unix.process_status
>>
`wait_pid p' suspends the execution of the calling thread until
the Unix process specified by the process identifier `p'
terminates. A pid `p' of `-1' means wait for any child. A pid of
`0' means wait for any child in the same process group as the
current process. Negative pid arguments represent process
groups. Returns the pid of the child caught and its termination
status, as per `Unix.wait'.
<<
val wait_signal : int list -> int
>>
`wait_signal sigs' suspends the execution of the calling thread
until the process receives one of the signals specified in the
list `sigs'. It then returns the number of the signal received.
Signal handlers attached to the signals in `sigs' will not be
invoked. Do not call `wait_signal' concurrently from several
threads on the same signals.
<<
val yield : unit -> unit
>>
Re-schedule the calling thread without suspending it. This
function can be used to give scheduling hints, telling the
scheduler that now is a good time to switch to other threads.
23.2 Module Mutex: locks for mutual exclusion
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
Mutexes (mutual-exclusion locks) are used to implement critical
sections and protect shared mutable data structures against
concurrent accesses. The typical use is (if `m' is the mutex
associated with the data structure `D'):
<<
Mutex.lock m;
(* Critical section that operates over D *);
Mutex.unlock m
>>
<<
type t
>>
The type of mutexes.
<<
val create: unit -> t
>>
Return a new mutex.
<<
val lock: t -> unit
>>
Lock the given mutex. Only one thread can have the mutex locked
at any time. A thread that attempts to lock a mutex already
locked by another thread will suspend until the other thread
unlocks the mutex.
<<
val try_lock: t -> bool
>>
Same as `try_lock', but does not suspend the calling thread if
the mutex is already locked: just return `false' immediately in
that case. If the mutex is unlocked, lock it and return `true'.
<<
val unlock: t -> unit
>>
Unlock the given mutex. Other threads suspended trying to lock
the mutex will restart.
23.3 Module Condition: condition variables to synchronize between threads
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
Condition variables are used when one thread wants to wait
until another thread has finished doing something: the former
thread ``waits'' on the condition variable, the latter thread
``signals'' the condition when it is done. Condition variables
should always be protected by a mutex. The typical use is (if
`D' is a shared data structure, `m' its mutex, and `c' is a
condition variable):
<<
Mutex.lock m;
while (* some predicate P over D is not satisfied *) do
Condition.wait c m
done;
(* Modify D *)
if (* the predicate P over D is now satified *) then
Condition.signal c;
Mutex.unlock m
>>
<<
type t
>>
The type of condition variables.
<<
val create: unit -> t
>>
Return a new condition variable.
<<
val wait: t -> locking:Mutex.t -> unit
>>
`wait c m' atomically unlocks the mutex `m' and suspends the
calling process on the condition variable `c'. The process will
restart after the condition variable `c' has been signalled. The
mutex `m' is locked again before `wait' returns.
<<
val signal: t -> unit
>>
`signal c' restarts one of the processes waiting on the
condition variable `c'.
<<
val broadcast: t -> unit
>>
`broadcast c' restarts all processes waiting on the condition
variable `c'.
23.4 Module Event: first-class synchronous communication
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module implements synchronous inter-thread communications
over channels. As in John Reppy's Concurrent ML system, the
communication events are first-class values: they can be built
and combined independently before being offered for
communication.
<<
type 'a channel
>>
The type of communication channels carrying values of type
`'a'.
<<
val new_channel: unit -> 'a channel
>>
Return a new channel.
<<
type 'a event
>>
The type of communication events returning a result of type
`'a'.
<<
val send: 'a channel -> 'a -> unit event
>>
`send ch v' returns the event consisting in sending the value
`v' over the channel `ch'. The result value of this event is
`()'.
<<
val receive: 'a channel -> 'a event
>>
`receive ch' returns the event consisting in receiving a value
from the channel `ch'. The result value of this event is the
value received.
<<
val always: 'a -> 'a event
>>
`always v' returns an event that is always ready for
synchronization. The result value of this event is `v'.
<<
val choose: 'a event list -> 'a event
>>
`choose evl' returns the event that is the alternative of all
the events in the list `evl'.
<<
val wrap: 'a event -> f:('a -> 'b) -> 'b event
>>
`wrap ev fn' returns the event that performs the same
communications as `ev', then applies the post-processing
function `fn' on the return value.
<<
val wrap_abort: 'a event -> f:(unit -> unit) -> 'a event
>>
`wrap_abort ev fn' returns the event that performs the same
communications as `ev', but if it is not selected the function
`fn' is called after the synchronization.
<<
val guard: (unit -> 'a event) -> 'a event
>>
`guard fn' returns the event that, when synchronized, computes
`fn()' and behaves as the resulting event. This allows to
compute events with side-effects at the time of the
synchronization operation.
<<
val sync: 'a event -> 'a
>>
``Synchronize'' on an event: offer all the communication
possibilities specified in the event to the outside world, and
block until one of the communications succeed. The result value
of that communication is returned.
<<
val select: 'a event list -> 'a
>>
``Synchronize'' on an alternative of events. `select evl' is
shorthand for `sync(choose evl)'.
<<
val poll: 'a event -> 'a option
>>
Non-blocking version of `sync': offer all the communication
possibilities specified in the event to the outside world, and
if one can take place immediately, perform it and return `Some
r' where `r' is the result value of that communication.
Otherwise, return `None' without blocking.
23.5 Module ThreadUnix: thread-compatible system calls
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module is deprecated: its functionality has been merged
back into the `Unix' module. Threaded programs can now call the
functions from module `Unix' directly, and still get the correct
behavior (block the calling thread, if required, but do not
block all threads in the process).
Process handling
=================
<<
val execv : prog:string -> args:string array -> unit
val execve : prog:string -> args:string array -> env:string array -> unit
val execvp : prog:string -> args:string array -> unit
val wait : unit -> int * Unix.process_status
val waitpid : mode:Unix.wait_flag list -> int -> int * Unix.process_status
val system : string -> Unix.process_status
>>
Basic input/output
===================
<<
val read : Unix.file_descr -> buf:string -> pos:int -> len:int -> int
val write : Unix.file_descr -> buf:string -> pos:int -> len:int -> int
>>
Input/output with timeout
==========================
<<
val timed_read :
Unix.file_descr ->
buf:string -> pos:int -> len:int -> timeout:float -> int
val timed_write :
Unix.file_descr ->
buf:string -> pos:int -> len:int -> timeout:float -> int
>>
Behave as `read' and `write', except that
`Unix_error(ETIMEDOUT,_,_)' is raised if no data is available
for reading or ready for writing after `d' seconds. The delay
`d' is given in the fifth argument, in seconds.
Polling
========
<<
val select :
read:Unix.file_descr list -> write:Unix.file_descr list ->
except:Unix.file_descr list -> timeout:float ->
Unix.file_descr list * Unix.file_descr list * Unix.file_descr list
>>
Pipes and redirections
=======================
<<
val pipe : unit -> Unix.file_descr * Unix.file_descr
val open_process_in: string -> in_channel
val open_process_out: string -> out_channel
val open_process: string -> in_channel * out_channel
val open_process_full:
string -> env:string array -> in_channel * out_channel * in_channel
>>
Time
=====
<<
val sleep : int -> unit
>>
Sockets
========
<<
val socket : domain:Unix.socket_domain ->
kind:Unix.socket_type -> protocol:int -> Unix.file_descr
val socketpair : domain:Unix.socket_domain -> kind:Unix.socket_type ->
protocol:int -> Unix.file_descr * Unix.file_descr
val accept : Unix.file_descr -> Unix.file_descr * Unix.sockaddr
val connect : Unix.file_descr -> addr:Unix.sockaddr -> unit
val recv : Unix.file_descr -> buf:string ->
pos:int -> len:int -> mode:Unix.msg_flag list -> int
val recvfrom : Unix.file_descr -> buf:string -> pos:int -> len:int ->
mode:Unix.msg_flag list -> int * Unix.sockaddr
val send : Unix.file_descr -> buf:string -> pos:int -> len:int ->
mode:Unix.msg_flag list -> int
val sendto : Unix.file_descr -> buf:string -> pos:int -> len:int ->
mode:Unix.msg_flag list -> addr:Unix.sockaddr -> int
val open_connection : Unix.sockaddr -> in_channel * out_channel
val establish_server :
(in_channel -> out_channel -> unit) ->
addr:Unix.sockaddr -> unit
>>
Chapter 24 The graphics library
***********************************
The graphics library provides a set of portable drawing primitives. Drawing
takes place in a separate window that is created when open_graph is called.
Unix:
This library is implemented under the X11 windows system.
Programs that use the graphics library must be linked as
follows:
<<
ocamlc other options graphics.cma other files
>>
For interactive use of the graphics library, do:
<<
ocamlmktop -o mytop graphics.cma
./mytop
>>
Here are the graphics mode specifications supported by
open_graph on the X11 implementation of this library: the
argument to open_graph has the format "display-name geometry",
where display-name is the name of the X-windows display to
connect to, and geometry is a standard X-windows geometry
specification. The two components are separated by a space.
Either can be omitted, or both. Examples:
open_graph "foo:0" connects to the display foo:0 and creates a
window with the default geometry
open_graph "foo:0 300x100+50-0" connects to the display foo:0
and creates a window 300 pixels wide by 100 pixels tall, at
location (50,0)
open_graph " 300x100+50-0" connects to the default display and
creates a window 300 pixels wide by 100 pixels tall, at
location (50,0)
open_graph "" connects to the default display and creates a
window with the default geometry.
Windows:
This library is available only under the toplevel application
ocamlwin.exe. Before using it, the Caml part of this library
must be loaded in-core, either by typing
<<
#load "graphics.cmo";;
>>
in the input windows or by using the ``Load'' entry of the
``File'' menu.
The screen coordinates are interpreted as shown in the figure below. Notice
that the coordinate system used is the same as in mathematics: y increases from
the bottom of the screen to the top of the screen, and angles are measured
counterclockwise (in degrees). Drawing is clipped to the screen.
*libgraph.gif*
24.1 Module Graphics: machine-independent graphics primitives
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
<<
exception Graphic_failure of string
>>
Raised by the functions below when they encounter an error.
Initializations
================
<<
val open_graph: string -> unit
>>
Show the graphics window or switch the screen to graphic mode.
The graphics window is cleared and the current point is set to
(0, 0). The string argument is used to pass optional information
on the desired graphics mode, the graphics window size, and so
on. Its interpretation is implementation-dependent. If the empty
string is given, a sensible default is selected.
<<
val close_graph: unit -> unit
>>
Delete the graphics window or switch the screen back to text
mode.
<<
val clear_graph : unit -> unit
>>
Erase the graphics window.
<<
val size_x : unit -> int
val size_y : unit -> int
>>
Return the size of the graphics window. Coordinates of the
screen pixels range over `0 .. size_x()-1' and `0 ..
size_y()-1'. Drawings outside of this rectangle are clipped,
without causing an error. The origin (0,0) is at the lower left
corner.
Colors
=======
<<
type color = int
>>
A color is specified by its R, G, B components. Each component
is in the range `0..255'. The three components are packed in an
`int': `0xRRGGBB', where `RR' are the two hexadecimal digits for
the red component, `GG' for the green component, `BB' for the
blue component.
<<
val rgb: int -> int -> int -> color
>>
`rgb r g b' returns the integer encoding the color with red
component `r', green component `g', and blue component `b'. `r',
`g' and `b' are in the range `0..255'.
<<
val set_color : color -> unit
>>
Set the current drawing color.
<<
val black : color
val white : color
val red : color
val green : color
val blue : color
val yellow : color
val cyan : color
val magenta : color
>>
Some predefined colors.
<<
val background: color
val foreground: color
>>
Default background and foreground colors (usually, either black
foreground on a white background or white foreground on a black
background). `clear_graph' fills the screen with the
`background' color. The initial drawing color is `foreground'.
Point and line drawing
=======================
<<
val plot : x:int -> y:int -> unit
>>
Plot the given point with the current drawing color.
<<
val point_color : x:int -> y:int -> color
>>
Return the color of the given point in the backing store (see
"Double buffering" below).
<<
val moveto : x:int -> y:int -> unit
>>
Position the current point.
<<
val rmoveto : dx:int -> dy:int -> unit
>>
`rmoveto dx dy' translates the current point by the given
vector.
<<
val current_x : unit -> int
>>
Return the abscissa of the current point.
<<
val current_y : unit -> int
>>
Return the ordinate of the current point.
<<
val current_point : unit -> int * int
>>
Return the position of the current point.
<<
val lineto : x:int -> y:int -> unit
>>
Draw a line with endpoints the current point and the given
point, and move the current point to the given point.
<<
val rlineto : dx:int -> dy:int -> unit
>>
Draws a line with endpoints the current point and the current
point translated of the given vector, and move the current point
to this point.
<<
val draw_rect : x:int -> y:int -> w:int -> h:int -> unit
>>
`draw_rect x y w h' draws the rectangle with lower left corner
at `x,y', width `w' and height `h'. The current point is
unchanged.
<<
val draw_arc :
x:int -> y:int -> rx:int -> ry:int -> start:int -> stop:int -> unit
>>
`draw_arc x y rx ry a1 a2' draws an elliptical arc with center
`x,y', horizontal radius `rx', vertical radius `ry', from angle
`a1' to angle `a2' (in degrees). The current point is unchanged.
<<
val draw_ellipse : x:int -> y:int -> rx:int -> ry:int -> unit
>>
`draw_ellipse x y rx ry' draws an ellipse with center `x,y',
horizontal radius `rx' and vertical radius `ry'. The current
point is unchanged.
<<
val draw_circle : x:int -> y:int -> r:int -> unit
>>
`draw_circle x y r' draws a circle with center `x,y' and radius
`r'. The current point is unchanged.
<<
val set_line_width : int -> unit
>>
Set the width of points and lines drawn with the functions
above. Under X Windows, `set_line_width 0' selects a width of 1
pixel and a faster, but less precise drawing algorithm than the
one used when `set_line_width 1' is specified.
Text drawing
=============
<<
val draw_char : char -> unit
val draw_string : string -> unit
>>
Draw a character or a character string with lower left corner
at current position. After drawing, the current position is set
to the lower right corner of the text drawn.
<<
val set_font : string -> unit
val set_text_size : int -> unit
>>
Set the font and character size used for drawing text. The
interpretation of the arguments to `set_font' and
`set_text_size' is implementation-dependent.
<<
val text_size : string -> int * int
>>
Return the dimensions of the given text, if it were drawn with
the current font and size.
Filling
========
<<
val fill_rect : x:int -> y:int -> w:int -> h:int -> unit
>>
`fill_rect x y w h' fills the rectangle with lower left corner
at `x,y', width `w' and height `h', with the current color.
<<
val fill_poly : (int * int) array -> unit
>>
Fill the given polygon with the current color. The array
contains the coordinates of the vertices of the polygon.
<<
val fill_arc :
x:int -> y:int -> rx:int -> ry:int -> start:int -> stop:int -> unit
>>
Fill an elliptical pie slice with the current color. The
parameters are the same as for `draw_arc'.
<<
val fill_ellipse : x:int -> y:int -> rx:int -> ry:int -> unit
>>
Fill an ellipse with the current color. The parameters are the
same as for `draw_ellipse'.
<<
val fill_circle : x:int -> y:int -> r:int -> unit
>>
Fill a circle with the current color. The parameters are the
same as for `draw_circle'.
Images
=======
<<
type image
>>
The abstract type for images, in internal representation.
Externally, images are represented as matrices of colors.
<<
val transp : color
>>
In matrices of colors, this color represent a ``transparent''
point: when drawing the corresponding image, all pixels on the
screen corresponding to a transparent pixel in the image will
not be modified, while other points will be set to the color of
the corresponding point in the image. This allows superimposing
an image over an existing background.
<<
val make_image : color array array -> image
>>
Convert the given color matrix to an image. Each sub-array
represents one horizontal line. All sub-arrays must have the
same length; otherwise, exception `Graphic_failure' is raised.
<<
val dump_image : image -> color array array
>>
Convert an image to a color matrix.
<<
val draw_image : image -> x:int -> y:int -> unit
>>
Draw the given image with lower left corner at the given point.
<<
val get_image : x:int -> y:int -> w:int -> h:int -> image
>>
Capture the contents of a rectangle on the screen as an image.
The parameters are the same as for `fill_rect'.
<<
val create_image : w:int -> h:int -> image
>>
`create_image w h' returns a new image `w' pixels wide and `h'
pixels tall, to be used in conjunction with `blit_image'. The
initial image contents are random, except that no point is
transparent.
<<
val blit_image : image -> x:int -> y:int -> unit
>>
`blit_image img x y' copies screen pixels into the image `img',
modifying `img' in-place. The pixels copied are those inside the
rectangle with lower left corner at `x,y', and width and height
equal to those of the image. Pixels that were transparent in
`img' are left unchanged.
Mouse and keyboard events
==========================
<<
type status =
{ mouse_x : int; (* X coordinate of the mouse *)
mouse_y : int; (* Y coordinate of the mouse *)
button : bool; (* true if a mouse button is pressed *)
keypressed : bool; (* true if a key has been pressed *)
key : char } (* the character for the key pressed *)
>>
To report events.
<<
type event =
Button_down (* A mouse button is pressed *)
| Button_up (* A mouse button is released *)
| Key_pressed (* A key is pressed *)
| Mouse_motion (* The mouse is moved *)
| Poll (* Don't wait; return immediately *)
>>
To specify events to wait for.
<<
val wait_next_event : event list -> status
>>
Wait until one of the events specified in the given event list
occurs, and return the status of the mouse and keyboard at that
time. If `Poll' is given in the event list, return immediately
with the current status. If the mouse cursor is outside of the
graphics window, the `mouse_x' and `mouse_y' fields of the event
are outside the range `0..size_x()-1, 0..size_y()-1'. Keypresses
are queued, and dequeued one by one when the `Key_pressed' event
is specified.
Mouse and keyboard polling
===========================
<<
val mouse_pos : unit -> int * int
>>
Return the position of the mouse cursor, relative to the
graphics window. If the mouse cursor is outside of the graphics
window, `mouse_pos()' returns a point outside of the range
`0..size_x()-1, 0..size_y()-1'.
<<
val button_down : unit -> bool
>>
Return `true' if the mouse button is pressed, `false'
otherwise.
<<
val read_key : unit -> char
>>
Wait for a key to be pressed, and return the corresponding
character. Keypresses are queued.
<<
val key_pressed : unit -> bool
>>
Return `true' if a keypress is available; that is, if
`read_key' would not block.
Sound
======
<<
val sound : freq:int -> ms:int -> unit
>>
`sound freq dur' plays a sound at frequency `freq' (in hertz)
for a duration `dur' (in milliseconds).
Double buffering
=================
<<
val auto_synchronize : bool -> unit
>>
By default, drawing takes place both on the window displayed on
screen, and in a memory area (the ``backing store''). The
backing store image is used to re-paint the on-screen window
when necessary.
To avoid flicker during animations, it is possible to turn off
on-screen drawing, perform a number of drawing operations in the
backing store only, then refresh the on-screen window
explicitly.
`auto_synchronize false' turns on-screen drawing off. All
subsequent drawing commands are performed on the backing store
only.
`auto_synchronize true' refreshes the on-screen window from the
backing store (as per `synchronize'), then turns on-screen
drawing back on. All subsequent drawing commands are performed
both on screen and in the backing store.
The default drawing mode corresponds to `auto_synchronize true'.
<<
val synchronize : unit -> unit
>>
Synchronize the backing store and the on-screen window, by
copying the contents of the backing store onto the graphics
window.
<<
val display_mode : bool -> unit
>>
Set display mode on or off. When turned on, drawings are done
in the graphics window; when turned off, drawings do not affect
the graphics window. This occurs independently of drawing into
the backing store (see the function `remember_mode' below).
Default display mode is on.
<<
val remember_mode : bool -> unit
>>
Set remember mode on or off. When turned on, drawings are done
in the backing store; when turned off, the backing store is
unaffected by drawings. This occurs independently of drawing
onto the graphics window (see the function `display_mode'
above). Default remember mode is on.
Chapter 25 The dbm library: access to NDBM databases
********************************************************
The dbm library provides access to NDBM databases under Unix. NDBM databases
maintain key/data associations, where both the key and the data are arbitrary
strings. They support fairly large databases (several gigabytes) and can
retrieve a keyed item in one or two file system accesses. Refer to the Unix
manual pages for more information.
Unix:
Programs that use the dbm library must be linked as follows:
<<
ocamlc other options dbm.cma other files
ocamlopt other options dbm.cmxa other files
>>
For interactive use of the dbm library, do:
<<
ocamlmktop -o mytop dbm.cma
./mytop
>>
Windows:
This library is not available.
25.1 Module Dbm: interface to the NDBM database
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
<<
type t
>>
The type of file descriptors opened on NDBM databases.
<<
type open_flag =
Dbm_rdonly | Dbm_wronly | Dbm_rdwr | Dbm_create
>>
Flags for opening a database (see `opendbm').
<<
exception Dbm_error of string
>>
Raised by the following functions when an error is encountered.
<<
val opendbm : string -> mode:open_flag list -> perm:int -> t
>>
Open a descriptor on an NDBM database. The first argument is
the name of the database (without the `.dir' and `.pag'
suffixes). The second argument is a list of flags: `Dbm_rdonly'
opens the database for reading only, `Dbm_wronly' for writing
only, `Dbm_rdwr' for reading and writing; `Dbm_create' causes
the database to be created if it does not already exist. The
third argument is the permissions to give to the database files,
if the database is created.
<<
val close : t -> unit
>>
Close the given descriptor.
<<
val find : t -> string -> string
>>
`find db key' returns the data associated with the given `key'
in the database opened for the descriptor `db'. Raise
`Not_found' if the `key' has no associated data.
<<
val add : t -> key:string -> data:string -> unit
>>
`add db key data' inserts the pair (`key', `data') in the
database `db'. If the database already contains data associated
with `key', raise `Dbm_error "Entry already exists"'.
<<
val replace : t -> key:string -> data:string -> unit
>>
`replace db key data' inserts the pair (`key', `data') in the
database `db'. If the database already contains data associated
with `key', that data is discarded and silently replaced by the
new `data'.
<<
val remove : t -> string -> unit
>>
`remove db key data' removes the data associated with `key' in
`db'. If `key' has no associated data, raise `Dbm_error
"dbm_delete"'.
<<
val firstkey : t -> string
val nextkey : t -> string
>>
Enumerate all keys in the given database, in an unspecified
order. `firstkey db' returns the first key, and repeated calls
to `nextkey db' return the remaining keys. `Not_found' is raised
when all keys have been enumerated.
<<
val iter : f:(key:string -> data:string -> 'a) -> t -> unit
>>
`iter f db' applies `f' to each (`key', `data') pair in the
database `db'. `f' receives `key' as first argument and `data'
as second argument.
Chapter 26 The dynlink library: dynamic loading and linking of object files
*******************************************************************************
The dynlink library supports type-safe dynamic loading and linking of
bytecode object files (.cmo and .cma files) in a running bytecode program. Type
safety is ensured by limiting the set of modules from the running program that
the loaded object file can access, and checking that the running program and
the loaded object file have been compiled against the same interfaces for these
modules.
Programs that use the dynlink library simply need to link dynlink.cma with
their object files and other libraries. Dynamic linking is available only to
bytecode programs compiled with ocamlc, not to native-code programs compiled
with ocamlopt.
26.1 Module Dynlink: dynamic loading of bytecode object files
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
<<
val init : unit -> unit
>>
Initialize the library. Must be called before `loadfile'.
<<
val loadfile : string -> unit
>>
Load the given bytecode object file and link it. All toplevel
expressions in the loaded compilation unit are evaluated. No
facilities are provided to access value names defined by the
unit. Therefore, the unit must register itself its entry points
with the main program, e.g. by modifying tables of functions.
<<
val loadfile_private : string -> unit
>>
Same as `loadfile', except that the module loaded is not made
available to other modules dynamically loaded afterwards.
<<
val add_interfaces : units:string list -> paths:string list -> unit
>>
`add_interfaces units path' grants dynamically-linked object
files access to the compilation units named in list `units'. The
interfaces (`.cmi' files) for these units are searched in `path'
(a list of directory names). Initially, dynamically-linked
object files do not have access to any of the compilation units
composing the running program, not even the standard library.
`add_interfaces' or `add_available_units' (see below) must be
called to grant access to some of the units.
<<
val add_available_units : (string * Digest.t) list -> unit
>>
Same as `add_interfaces', but instead of searching `.cmi' files
to find the unit interfaces, uses the interface digests given
for each unit. This way, the `.cmi' interface files need not be
available at run-time. The digests can be extracted from `.cmi'
files using the `extract_crc' program installed in the Objective
Caml standard library directory.
<<
val clear_available_units : unit -> unit
>>
Clear the list of compilation units accessible to
dynamically-linked programs.
<<
val allow_unsafe_modules : bool -> unit
>>
Govern whether unsafe object files are allowed to be
dynamically linked. A compilation unit is ``unsafe'' if it
contains declarations of external functions, which can break
type safety. By default, dynamic linking of unsafe object files
is not allowed.
<<
type linking_error =
Undefined_global of string
| Unavailable_primitive of string
| Uninitialized_global of string
type error =
Not_a_bytecode_file of string
| Inconsistent_import of string
| Unavailable_unit of string
| Unsafe_file
| Linking_error of string * linking_error
| Corrupted_interface of string
exception Error of error
>>
Errors in dynamic linking are reported by raising the `Error'
exception with a description of the error.
<<
val error_message: error -> string
>>
Convert an error description to a printable message.
Chapter 27 The LablTk library: Tcl/Tk GUI interface
*******************************************************
The labltk library provides access to the Tcl/Tk GUI from Objective Caml
programs. This interface is generated in an automated way, and you should refer
to Tcl/Tk books and man pages for detailed information on the behavior of the
numerous functions.
Programs that use the labltk library must be linked as follows:
<<
ocamlc other options -I labltk-dir labltk.cma other files
ocamlopt other options -I labltk-dir labltk.cmxa other files
>>
labltk-dir is CAMLLIB/labltk. On Unix the default location is
/usr/local/lib/caml/labltk.
Unix:
The labltk library is available for any system with Tcl/Tk
installed, starting from Tcl 7.5/Tk 4.1 up to Tcl/Tk 8.3. Beware
that some beta versions may have compatibility problems.
If the library was not compiled correctly, try to run again the
configure script with the option -tkdefs switches, where
switches is a list of C-style inclusion paths leading to the
right tcl.h and tk.h, for instance '-I/usr/local/include/tcl8.0
-I/usr/local/include/tk8.0'.
A script is installed, to make easier the use of the labltk
library as toplevel.
labltk This is a toplevel including the labltk library, and
the path is already set as to allow the use of the various
modules. It also includes code for the Unix and Str
libraries. You can use it in place of ocaml.
Windows:
The labltk library has been precompiled for use with Tcl/Tk
8.0. You must first have it installed on your system. It can be
downloaded from
http://www.scriptics.com/products/tcltk/8.0.html. After
installing it, you must put the dynamically loaded libraries
tcl80.dll and tk80.dll (from the bin directory of the Tcl
installation) in a directory included in you path.
The toplevel, including Unix and Str, is available as labltk.
But you need to explicitly add the labltk library directory to
your load path with the #directory directive.
The labltk library is composed of a large number of modules.
<<
Bell Imagebitmap Place
Button Imagephoto Radiobutton
Canvas Label Scale
Checkbutton Listbox Scrollbar
Clipboard Menu Selection
Dialog Menubutton Text
Entry Message Tk
Focus Option Tkwait
Frame Optionmenu Toplevel
Grab Pack Winfo
Grid Palette Wm
>>
Giving a detailed account of each of these module would be impractical here.
We will just present some of the basic functions in the module Tk. Note that
for most other modules information can be found in the Tcl man page of their
name.
27.1 Module Tk: basic functions and types for LablTk
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Initialization and termination
===============================
<<
val openTk : ?display:string -> ?class:string -> unit -> toplevel widget
>>
Initialize LablTk and open a toplevel window. `display' is
described according to the X11 conventions. `class' is used for
the X11 resource mechanism.
<<
val mainLoop : unit -> unit
>>
Start the main event loop
<<
val closeTk : unit -> unit
>>
Quit the main loop and close all open windows.
<<
val destroy : 'a Widget.widget -> unit
>>
Destroy an individual widget.
Application wide commands
==========================
<<
val update : unit -> unit
>>
Synchronize display with internal state.
<<
val appname_get : unit -> string
val appname_set : string -> unit
>>
Get or set the application name.
Dimensions
===========
<<
type units = [`Pix int|`Cm float|`In float|`Mm float|`Pt float]
val pixels : units -> int
>>
Converts various on-screen units to pixels, respective to the
default display. Available units are pixels, centimeters,
inches, millimeters and points
Widget layout commands
=======================
<<
type anchor = [`Center|`E|`N|`Ne|`Nw|`S|`Se|`Sw|`W]
type fillMode = [`Both|`None|`X|`Y]
type side = [`Bottom|`Left|`Right|`Top]
val pack :
?after:'a Widget.widget ->
?anchor:anchor ->
?before:'b Widget.widget ->
?expand:bool ->
?fill:fillMode ->
?inside:'c Widget.widget ->
?ipadx:int ->
?ipady:int ->
?padx:int ->
?pady:int ->
?side:side ->
'd Widget.widget list -> unit
>>
Pack a widget inside its parent, using the standard layout
engine.
<<
val grid :
?column:int ->
?columnspan:int ->
?inside:'a Widget.widget ->
?ipadx:int ->
?ipady:int ->
?padx:int ->
?pady:int ->
?row:int ->
?rowspan:int ->
?sticky:string -> 'b Widget.widget list -> unit
>>
Pack a widget inside its parent, using the grid layout engine.
<<
type borderMode = [`Ignore|`Inside|`Outside]
val place :
?anchor:anchor ->
?bordermode:borderMode ->
?height:int ->
?inside:'a Widget.widget ->
?relheight:float ->
?relwidth:float ->
?relx:float ->
?rely:float ->
?width:int ->
?x:int -> ?y:int -> 'b Widget.widget -> unit
>>
Pack a widget inside its parent, at absolute coordinates.
<<
val raise_window :
?above:'a Widget.widget -> 'b Widget.widget -> unit
val lower_window :
?below:'a Widget.widget -> 'b Widget.widget -> unit
>>
Raise or lower the window associated to a widget.
Event handling
===============
<<
type modifier =
[ `Control | `Shift | `Lock
| `Button1 | `Button2 | `Button3 | `Button4 | `Button5
| `Double | `Triple
| `Mod1 | `Mod2 | `Mod3 | `Mod4 | `Mod5 | `Meta | `Alt ]
type event =
[ `ButtonPress | `ButtonPressDetail int
| `ButtonRelease | `ButtonReleaseDetail int
| `Circulate | `ColorMap | `Configure | `Destroy
| `Enter | `Expose | `FocusIn | `FocusOut | `Gravity
| `KeyPress | `KeyPressDetail string
| `KeyRelease | `KeyReleaseDetail string
| `Leave | `Map | `Motion | `Property
| `Reparent | `Unmap | `Visibility
| `Modified modifier list * event ]
>>
An event can be either a basic X event, or modified by a key or
mouse modifier.
<<
type eventInfo =
{ mutable ev_Above: int;
mutable ev_ButtonNumber: int;
mutable ev_Count: int;
mutable ev_Detail: string;
mutable ev_Focus: bool;
mutable ev_Height: int;
mutable ev_KeyCode: int;
mutable ev_Mode: string;
mutable ev_OverrideRedirect: bool;
mutable ev_Place: string;
mutable ev_State: string;
mutable ev_Time: int;
mutable ev_Width: int;
mutable ev_MouseX: int;
mutable ev_MouseY: int;
mutable ev_Char: string;
mutable ev_BorderWidth: int;
mutable ev_SendEvent: bool;
mutable ev_KeySymString: string;
mutable ev_KeySymInt: int;
mutable ev_RootWindow: int;
mutable ev_SubWindow: int;
mutable ev_Type: int;
mutable ev_Widget: Widget.any Widget.widget;
mutable ev_RootX: int;
mutable ev_RootY: int }
>>
Event related information accessible in callbacks.
<<
type eventField =
[ `Above | `ButtonNumber | `Count | `Detail | `Focus | `Height
| `KeyCode | `Mode | `OverrideRedirect | `Place | `State
| `Time | `Width | `MouseX | `MouseY | `Char | `BorderWidth
| `SendEvent | `KeySymString | `KeySymInt | `RootWindow
| `SubWindow | `Type | `Widget | `RootX | `RootY ]
>>
In order to access the above event information, one has to pass
a list of required event fields to the `bind' function.
<<
val bind :
events:event list ->
?extend:bool ->
?breakable:bool ->
?fields:eventField list
?action:(eventInfo -> unit) ->
'a Widget.widget -> unit
>>
Bind a succession of `events' on a widget to an `action'. If
`extend' is true then then binding is added after existing ones,
otherwise it replaces them. `breakable' should be true when
`break' is to be called inside the action. `action' is called
with the `fields' required set in an `eventInfo' structure.
Other fields should not be accessed. If `action' is omitted then
existing bindings are removed.
<<
val bind_class :
events:event list ->
?extend:bool ->
?breakable:bool ->
?fields:eventField list
?action:(eventInfo -> unit) ->
?on:'a Widget.widget ->
string -> unit
>>
Same thing for all widgets of a given class. If a widget is
given with label `~on:', the binding will be removed as soon as
it is destroyed.
<<
val bind_tag :
events:event list ->
?extend:bool ->
?breakable:bool ->
?fields:eventField list
?action:(eventInfo -> unit) ->
?on:'a Widget.widget ->
string -> unit
>>
Same thing for all widgets having a given tag
<<
val break : unit -> unit
>>
Used inside a bound action, do not call other actions after
this one. This is only possible if this action was bound with
`~breakable:true'.
Chapter 28 The bigarray library
***********************************
The bigarray library implements large, multi-dimensional, numerical arrays.
These arrays are called ``big arrays'' to distinguish them from the standard
Caml arrays described in section 19.2. The main differences between ``big
arrays'' and standard Caml arrays are as follows:
- Big arrays are not limited in size, unlike Caml arrays (float array are
limited to 2097151 elements on a 32-bit platform, other array types to
4194303 elements).
- Big arrays are multi-dimensional. Any number of dimensions between 1 and 16
is supported. In contrast, Caml arrays are mono-dimensional and require
encoding multi-dimensional arrays as arrays of arrays.
- Big arrays can only contain integers and floating-point numbers, while Caml
arrays can contain arbitrary Caml data types. However, big arrays provide
more space-efficient storage of integer and floating-point elements, in
particular because they support ``small'' types such as single-precision
floats and 8 and 16-bit integers, in addition to the standard Caml types of
double-precision floats and 32 and 64-bit integers.
- The memory layout of big arrays is entirely compatible with that of arrays
in C and Fortran, allowing large arrays to be passed back and forth between
Caml code and C / Fortran code with no data copying at all.
- Big arrays support interesting high-level operations that normal arrays do
not provide efficiently, such as extracting sub-arrays and ``slicing'' a
multi-dimensional array along certain dimensions, all without any copying.
Programs that use the bigarray library must be linked as follows:
<<
ocamlc other options bigarray.cma other files
ocamlopt other options bigarray.cmxa other files
>>
For interactive use of the bigarray library, do:
<<
ocamlmktop -o mytop bigarray.cma
./mytop
>>
28.1 Module Bigarray: large, multi-dimensional, numerical arrays
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module implements multi-dimensional arrays of integers and
floating-point numbers, thereafter referred to as ``big
arrays''. The implementation allows efficient sharing of large
numerical arrays between Caml code and C or Fortran numerical
libraries.
Concerning the naming conventions, users of this module are
encouraged to do `open Bigarray' in their source, then refer to
array types and operations via short dot notation, e.g.
`Array1.t' or `Array2.sub'.
Big arrays support all the Caml ad-hoc polymorphic operations:
comparisons (`=', `<>', `<=', etc, as well as `compare');
hashing (module `Hash'); and structured input-output
(`output_value' and `input_value', as well as the functions from
the `Marshal' module).
Element kinds
==============
<<
type float32_elt
type float64_elt
type int8_signed_elt
type int8_unsigned_elt
type int16_signed_elt
type int16_unsigned_elt
type int_elt
type int32_elt
type int64_elt
type nativeint_elt
>>
Big arrays can contain elements of the following kinds:
IEEE single precision (32 bits) floating-point numbers;
IEEE double precision (64 bits) floating-point numbers;
8-bit integers (signed or unsigned);
16-bit integers (signed or unsigned);
Caml integers (signed, 31 bits on 32-bit architectures, 63 bits
on 64-bit architectures);
32-bit signed integers;
64-bit signed integers;
platform-native signed integers (32 bits on 32-bit
architectures, 64 bits on 64-bit architectures).
Each element kind is represented at the type level by one of the
abstract types defined above.
<<
type ('a, 'b) kind
>>
To each element kind is associated a Caml type, which is the
type of Caml values that can be stored in the big array or read
back from it. This type is not necessarily the same as the type
of the array elements proper: for instance, a big array whose
elements are of kind `float32_elt' contains 32-bit single
precision floats, but reading or writing one of its elements
from Caml uses the Caml type `float', which is 64-bit double
precision floats.
The abstract type `('a, 'b) kind' captures this association of a
Caml type `'a' for values read or written in the big array, and
of an element kind `'b' which represents the actual contents of
the big array. The following predefined values of type `kind'
list all possible associations of Caml types with element kinds:
<<
val float32: (float, float32_elt) kind
val float64: (float, float64_elt) kind
val int8_signed: (int, int8_signed_elt) kind
val int8_unsigned: (int, int8_unsigned_elt) kind
val int16_signed: (int, int16_signed_elt) kind
val int16_unsigned: (int, int16_unsigned_elt) kind
val int: (int, int_elt) kind
val int32: (int32, int32_elt) kind
val int64: (int64, int64_elt) kind
val nativeint: (nativeint, nativeint_elt) kind
val char: (char, int8_unsigned_elt) kind
>>
As shown by the types of the values above, big arrays of kind
`float32_elt' and `float64_elt' are accessed using the Caml type
`float'. Big arrays of integer kinds are accessed using the
smallest Caml integer type large enough to represent the array
elements: `int' for 8- and 16-bit integer bigarrays, as well as
Caml-integer bigarrays; `int32' for 32-bit integer bigarrays;
`int64' for 64-bit integer bigarrays; and `nativeint' for
platform-native integer bigarrays. Finally, big arrays of kind
`int8_unsigned_elt' can also be accessed as arrays of characters
instead of arrays of small integers, by using the kind value
`char' instead of `int8_unsigned'.
Array layouts
==============
<<
type c_layout
type fortran_layout
>>
To facilitate interoperability with existing C and Fortran
code, this library supports two different memory layouts for big
arrays, one compatible with the C conventions, the other
compatible with the Fortran conventions.
In the C-style layout, array indices start at 0, and
multi-dimensional arrays are laid out in row-major format. That
is, for a two-dimensional array, all elements of row 0 are
contiguous in memory, followed by all elements of row 1, etc. In
other terms, the array elements at `(x,y)' and `(x, y+1)' are
adjacent in memory.
In the Fortran-style layout, array indices start at 1, and
multi-dimensional arrays are laid out in column-major format.
That is, for a two-dimensional array, all elements of column 0
are contiguous in memory, followed by all elements of column 1,
etc. In other terms, the array elements at `(x,y)' and `(x+1,
y)' are adjacent in memory.
Each layout style is identified at the type level by the
abstract types `c_layout' and `fortran_layout' respectively.
<<
type 'a layout
>>
The type `'a layout' represents one of the two supported memory
layouts: C-style if `'a' is `c_layout', Fortran-style if `'a' is
`fortran_layout'.
<<
val c_layout: c_layout layout
val fortran_layout: fortran_layout layout
>>
The abstract values `c_layout' and `fortran_layout' represent
the two supported layouts at the level of values.
Generic arrays (of arbitrarily many dimensions)
================================================
<<
module Genarray: sig
type ('a, 'b, 'c) t
>>
The type `Genarray.t' is the type of big arrays with variable
numbers of dimensions. Any number of dimensions between 1 and 16
is supported.
The three type parameters to `Genarray.t' identify the array
element kind and layout, as follows:
the first parameter, `'a', is the Caml type for accessing array
elements (`float', `int', `int32', `int64', `nativeint');
the second parameter, `'b', is the actual kind of array elements
(`float32_elt', `float64_elt', `int8_signed_elt',
`int8_unsigned_elt', etc);
the third parameter, `'c', identifies the array layout
(`c_layout' or `fortran_layout').
For instance, `(float, float32_elt, fortran_layout) Genarray.t'
is the type of generic big arrays containing 32-bit floats in
Fortran layout; reads and writes in this array use the Caml type
`float'.
<<
external create:
kind:('a, 'b) kind -> layout:'c layout -> dims:int array -> ('a, 'b, 'c)
t
>>
`Genarray.create kind layout dimensions' returns a new big
array whose element kind is determined by the parameter `kind'
(one of `float32', `float64', `int8_signed', etc) and whose
layout is determined by the parameter `layout' (one of
`c_layout' or `fortran_layout'). The `dimensions' parameter is
an array of integers that indicate the size of the big array in
each dimension. The length of `dimensions' determines the number
of dimensions of the bigarray.
For instance, `Genarray.create int32 c_layout [|4;6;8|]' returns
a fresh big array of 32-bit integers, in C layout, having three
dimensions, the three dimensions being 4, 6 and 8 respectively.
Big arrays returned by `Genarray.create' are not initialized:
the initial values of array elements is unspecified.
`Genarray.create' raises `Invalid_arg' if the number of
dimensions is not in the range 1 to 16 inclusive, or if one of
the dimensions is negative.
<<
external num_dims: ('a, 'b, 'c) t -> int
>>
Return the number of dimensions of the given big array.
<<
external nth_dim: ('a, 'b, 'c) t -> int -> int
>>
`Genarray.nth_dim a n' returns the `n'-th dimension of the big
array `a'. The first dimension corresponds to `n = 0'; the
second dimension corresponds to `n = 1'; the last dimension, to
`n = Genarray.num_dims a - 1'. Raise `Invalid_arg' if `n' is
less than 0 or greater or equal than `Genarray.num_dims a'.
<<
external get: ('a, 'b, 'c) t -> int array -> 'a
>>
Read an element of a generic big array. `Genarray.get a [|i1;
...; iN|]' returns the element of `a' whose coordinates are `i1'
in the first dimension, `i2' in the second dimension, ..., `iN'
in the `N'-th dimension.
If `a' has C layout, the coordinates must be greater or equal
than 0 and strictly less than the corresponding dimensions of
`a'. If `a' has Fortran layout, the coordinates must be greater
or equal than 1 and less or equal than the corresponding
dimensions of `a'. Raise `Invalid_arg' if the array `a' does not
have exactly `N' dimensions, or if the coordinates are outside
the array bounds.
If `N > 3', alternate syntax is provided: you can write `a.{i1,
i2, ..., iN}' instead of `Genarray.get a [|i1; ...; iN|]'. (The
syntax `a.{...}' with one, two or three coordinates is reserved
for accessing one-, two- and three-dimensional arrays as
described below.)
<<
external set: ('a, 'b, 'c) t -> int array -> 'a -> unit
>>
Assign an element of a generic big array. `Genarray.set a [|i1;
...; iN|] v' stores the value `v' in the element of `a' whose
coordinates are `i1' in the first dimension, `i2' in the second
dimension, ..., `iN' in the `N'-th dimension.
The array `a' must have exactly `N' dimensions, and all
coordinates must lie inside the array bounds, as described for
`Genarray.get'; otherwise, `Invalid_arg' is raised.
If `N > 3', alternate syntax is provided: you can write `a.{i1,
i2, ..., iN} <- v' instead of `Genarray.set a [|i1; ...; iN|]
v'. (The syntax `a.{...} <- v' with one, two or three
coordinates is reserved for updating one-, two- and
three-dimensional arrays as described below.)
<<
external sub_left:
('a, 'b, c_layout) t -> pos:int -> len:int -> ('a, 'b, c_layout) t
>>
Extract a sub-array of the given big array by restricting the
first (left-most) dimension. `Genarray.sub_left a ofs len'
returns a big array with the same number of dimensions as `a',
and the same dimensions as `a', except the first dimension,
which corresponds to the interval `[ofs ... ofs + len - 1]' of
the first dimension of `a'. No copying of elements is involved:
the sub-array and the original array share the same storage
space. In other terms, the element at coordinates `[|i1; ...;
iN|]' of the sub-array is identical to the element at
coordinates `[|i1+ofs; ...; iN|]' of the original array `a'.
`Genarray.sub_left' applies only to big arrays in C layout.
Raise `Invalid_arg' if `ofs' and `len' do not designate a valid
sub-array of `a', that is, if `ofs < 0', or `len < 0', or `ofs +
len > Genarray.nth_dim a 0'.
<<
external sub_right:
('a, 'b, fortran_layout) t ->
pos:int -> len:int -> ('a, 'b, fortran_layout) t
>>
Extract a sub-array of the given big array by restricting the
last (right-most) dimension. `Genarray.sub_right a ofs len'
returns a big array with the same number of dimensions as `a',
and the same dimensions as `a', except the last dimension, which
corresponds to the interval `[ofs ... ofs + len - 1]' of the
last dimension of `a'. No copying of elements is involved: the
sub-array and the original array share the same storage space.
In other terms, the element at coordinates `[|i1; ...; iN|]' of
the sub-array is identical to the element at coordinates `[|i1;
...; iN+ofs|]' of the original array `a'.
`Genarray.sub_right' applies only to big arrays in Fortran
layout. Raise `Invalid_arg' if `ofs' and `len' do not designate
a valid sub-array of `a', that is, if `ofs < 1', or `len < 0',
or `ofs + len > Genarray.nth_dim a (Genarray.num_dims a - 1)'.
<<
external slice_left:
('a, 'b, c_layout) t -> int array -> ('a, 'b, c_layout) t
>>
Extract a sub-array of lower dimension from the given big array
by fixing one or several of the first (left-most) coordinates.
`Genarray.slice_left a [|i1; ... ; iM|]' returns the ``slice''
of `a' obtained by setting the first `M' coordinates to `i1',
..., `iM'. If `a' has `N' dimensions, the slice has dimension `N
- M', and the element at coordinates `[|j1; ...; j(N-M)|]' in
the slice is identical to the element at coordinates `[|i1; ...;
iM; j1; ...; j(N-M)|]' in the original array `a'. No copying of
elements is involved: the slice and the original array share the
same storage space.
`Genarray.slice_left' applies only to big arrays in C layout.
Raise `Invalid_arg' if `M >= N', or if `[|i1; ... ; iM|]' is
outside the bounds of `a'.
<<
external slice_right:
('a, 'b, fortran_layout) t -> int array -> ('a, 'b, fortran_layout) t
>>
Extract a sub-array of lower dimension from the given big array
by fixing one or several of the last (right-most) coordinates.
`Genarray.slice_right a [|i1; ... ; iM|]' returns the ``slice''
of `a' obtained by setting the last `M' coordinates to `i1',
..., `iM'. If `a' has `N' dimensions, the slice has dimension `N
- M', and the element at coordinates `[|j1; ...; j(N-M)|]' in
the slice is identical to the element at coordinates `[|j1; ...;
j(N-M); i1; ...; iM|]' in the original array `a'. No copying of
elements is involved: the slice and the original array share the
same storage space.
`Genarray.slice_right' applies only to big arrays in Fortran
layout. Raise `Invalid_arg' if `M >= N', or if `[|i1; ... ;
iM|]' is outside the bounds of `a'.
<<
external blit: src:('a, 'b, 'c) t -> dst:('a, 'b, 'c) t -> unit
>>
Copy all elements of a big array in another big array.
`Genarray.blit src dst' copies all elements of `src' into `dst'.
Both arrays `src' and `dst' must have the same number of
dimensions and equal dimensions. Copying a sub-array of `src' to
a sub-array of `dst' can be achieved by applying `Genarray.blit'
to sub-array or slices of `src' and `dst'.
<<
external fill: ('a, 'b, 'c) t -> 'a -> unit
>>
Set all elements of a big array to a given value.
`Genarray.fill a v' stores the value `v' in all elements of the
big array `a'. Setting only some elements of `a' to `v' can be
achieved by applying `Genarray.fill' to a sub-array or a slice
of `a'.
<<
external map_file:
Unix.file_descr -> kind:('a, 'b) kind -> layout:'c layout ->
shared:bool -> dims:int array -> ('a, 'b, 'c) t
>>
Memory mapping of a file as a big array. `Genarray.map_file fd
kind layout shared dims' returns a big array of kind `kind',
layout `layout', and dimensions as specified in `dims'. The data
contained in this big array are the contents of the file
referred to by the file descriptor `fd' (as opened previously
with `Unix.openfile', for example). If `shared' is `true', all
modifications performed on the array are reflected in the file.
This requires that `fd' be opened with write permissions. If
`shared' is `false', modifications performed on the array are
done in memory only, using copy-on-write of the modified pages;
the underlying file is not affected.
`Genarray.map_file' is much more efficient than reading the
whole file in a big array, modifying that big array, and writing
it afterwards.
To adjust automatically the dimensions of the big array to the
actual size of the file, the major dimension (that is, the first
dimension for an array with C layout, and the last dimension for
an array with Fortran layout) can be given as `-1'.
`Genarray.map_file' then determines the major dimension from the
size of the file. The file must contain an integral number of
sub-arrays as determined by the non-major dimensions, otherwise
`Failure' is raised.
If all dimensions of the big array are given, the file size is
matched against the size of the big array. If the file is larger
than the big array, only the initial portion of the file is
mapped to the big array. If the file is smaller than the big
array, the file is automatically grown to the size of the big
array. This requires write permissions on `fd'.
<<
end
>>
One-dimensional arrays
=======================
The `Array1' structure provides operations similar to those of
`Genarray', but specialized to the case of one-dimensional
arrays. (The `Array2' and `Array3' structures below provide
operations specialized for two- and three-dimensional arrays.)
Statically knowing the number of dimensions of the array allows
faster operations, and more precise static type-checking.
<<
module Array1: sig
type ('a, 'b, 'c) t
>>
The type of one-dimensional big arrays whose elements have Caml
type `'a', representation kind `'b', and memory layout `'c'.
<<
val create:
kind:('a, 'b) kind -> layout:'c layout -> dim:int -> ('a, 'b, 'c) t
>>
`Array1.create kind layout dim' returns a new bigarray of one
dimension, whose size is `dim'. `kind' and `layout' determine
the array element kind and the array layout as described for
`Genarray.create'.
<<
val dim: ('a, 'b, 'c) t -> int
>>
Return the size (dimension) of the given one-dimensional big
array.
<<
external get: ('a, 'b, 'c) t -> int -> 'a
>>
`Array1.get a x', or alternatively `a.{x}', returns the
element of `a' at index `x'. `x' must be greater or equal than
`0' and strictly less than `Array1.dim a' if `a' has C layout.
If `a' has Fortran layout, `x' must be greater or equal than `1'
and less or equal than `Array1.dim a'. Otherwise, `Invalid_arg'
is raised.
<<
external set: ('a, 'b, 'c) t -> int -> 'a -> unit
>>
`Array1.set a x v', also written `a.{x} <- v', stores the value
`v' at index `x' in `a'. `x' must be inside the bounds of `a' as
described in `Array1.get'; otherwise, `Invalid_arg' is raised.
<<
external sub: ('a, 'b, 'c) t -> pos:int -> len:int -> ('a, 'b, 'c) t
>>
Extract a sub-array of the given one-dimensional big array. See
`Genarray.sub_left' for more details.
<<
external blit: src:('a, 'b, 'c) t -> dst:('a, 'b, 'c) t -> unit
>>
Copy the first big array to the second big array. See
`Genarray.blit' for more details.
<<
external fill: ('a, 'b, 'c) t -> 'a -> unit
>>
Fill the given big array with the given value. See
`Genarray.fill' for more details.
<<
val of_array:
kind:('a, 'b) kind -> layout:'c layout -> 'a array -> ('a, 'b, 'c) t
>>
Build a one-dimensional big array initialized from the given
array.
<<
val map_file: Unix.file_descr -> kind:('a, 'b) kind -> layout:'c layout ->
shared:bool -> dim:int -> ('a, 'b, 'c) t
>>
Memory mapping of a file as a one-dimensional big array. See
`Genarray.map_file' for more details.
<<
end
>>
Two-dimensional arrays
=======================
The `Array2' structure provides operations similar to those of
`Genarray', but specialized to the case of two-dimensional
arrays.
<<
module Array2: sig
type ('a, 'b, 'c) t
>>
The type of two-dimensional big arrays whose elements have Caml
type `'a', representation kind `'b', and memory layout `'c'.
<<
val create:
kind:('a, 'b) kind ->
layout:'c layout -> dim1:int -> dim2:int -> ('a, 'b, 'c) t
>>
`Array2.create kind layout dim1 dim2' returns a new bigarray of
two dimension, whose size is `dim1' in the first dimension and
`dim2' in the second dimension. `kind' and `layout' determine
the array element kind and the array layout as described for
`Genarray.create'.
<<
val dim1: ('a, 'b, 'c) t -> int
>>
Return the first dimension of the given two-dimensional big
array.
<<
val dim2: ('a, 'b, 'c) t -> int
>>
Return the second dimension of the given two-dimensional big
array.
<<
external get: ('a, 'b, 'c) t -> int -> int -> 'a
>>
`Array2.get a x y', also written `a.{x,y}', returns the element
of `a' at coordinates (`x', `y'). `x' and `y' must be within the
bounds of `a', as described for `Genarray.get'; otherwise,
`Invalid_arg' is raised.
<<
external set: ('a, 'b, 'c) t -> int -> int -> 'a -> unit
>>
`Array2.set a x y v', or alternatively `a.{x,y} <- v', stores
the value `v' at coordinates (`x', `y') in `a'. `x' and `y' must
be within the bounds of `a', as described for `Genarray.set';
otherwise, `Invalid_arg' is raised.
<<
external sub_left:
('a, 'b, c_layout) t -> pos:int -> len:int -> ('a, 'b, c_layout) t
>>
Extract a two-dimensional sub-array of the given
two-dimensional big array by restricting the first dimension.
See `Genarray.sub_left' for more details. `Array2.sub_left'
applies only to arrays with C layout.
<<
external sub_right:
('a, 'b, fortran_layout) t ->
pos:int -> len:int -> ('a, 'b, fortran_layout) t
>>
Extract a two-dimensional sub-array of the given
two-dimensional big array by restricting the second dimension.
See `Genarray.sub_right' for more details. `Array2.sub_right'
applies only to arrays with Fortran layout.
<<
val slice_left:
('a, 'b, c_layout) t -> x:int -> ('a, 'b, c_layout) Array1.t
>>
Extract a row (one-dimensional slice) of the given
two-dimensional big array. The integer parameter is the index of
the row to extract. See `Genarray.slice_left' for more details.
`Array2.slice_left' applies only to arrays with C layout.
<<
val slice_right:
('a, 'b, fortran_layout) t -> y:int -> ('a, 'b, fortran_layout) Array1.t
>>
Extract a column (one-dimensional slice) of the given
two-dimensional big array. The integer parameter is the index of
the column to extract. See `Genarray.slice_right' for more
details. `Array2.slice_right' applies only to arrays with
Fortran layout.
<<
external blit: src:('a, 'b, 'c) t -> dst:('a, 'b, 'c) t -> unit
>>
Copy the first big array to the second big array. See
`Genarray.blit' for more details.
<<
external fill: ('a, 'b, 'c) t -> 'a -> unit
>>
Fill the given big array with the given value. See
`Genarray.fill' for more details.
<<
val of_array:
kind:('a, 'b) kind -> layout:'c layout -> 'a array array -> ('a, 'b, 'c)
t
>>
Build a two-dimensional big array initialized from the given
array of arrays.
<<
val map_file: Unix.file_descr -> kind:('a, 'b) kind -> layout:'c layout ->
shared:bool -> dim1:int -> dim2:int -> ('a, 'b, 'c) t
>>
Memory mapping of a file as a two-dimensional big array. See
`Genarray.map_file' for more details.
<<
end
>>
Three-dimensional arrays
=========================
The `Array3' structure provides operations similar to those of
`Genarray', but specialized to the case of three-dimensional
arrays.
<<
module Array3: sig
type ('a, 'b, 'c) t
>>
The type of three-dimensional big arrays whose elements have
Caml type `'a', representation kind `'b', and memory layout
`'c'.
<<
val create:
kind:('a, 'b) kind -> layout:'c layout ->
dim1:int -> dim2:int -> dim3:int -> ('a, 'b, 'c) t
>>
`Array3.create kind layout dim1 dim2 dim3' returns a new
bigarray of three dimension, whose size is `dim1' in the first
dimension, `dim2' in the second dimension, and `dim3' in the
third. `kind' and `layout' determine the array element kind and
the array layout as described for `Genarray.create'.
<<
val dim1: ('a, 'b, 'c) t -> int
>>
Return the first dimension of the given three-dimensional big
array.
<<
val dim2: ('a, 'b, 'c) t -> int
>>
Return the second dimension of the given three-dimensional big
array.
<<
val dim3: ('a, 'b, 'c) t -> int
>>
Return the third dimension of the given three-dimensional big
array.
<<
external get: ('a, 'b, 'c) t -> int -> int -> int -> 'a
>>
`Array3.get a x y z', also written `a.{x,y,z}', returns the
element of `a' at coordinates (`x', `y', `z'). `x', `y' and `z'
must be within the bounds of `a', as described for
`Genarray.get'; otherwise, `Invalid_arg' is raised.
<<
external set: ('a, 'b, 'c) t -> int -> int -> int -> 'a -> unit
>>
`Array3.set a x y v', or alternatively `a.{x,y,z} <- v', stores
the value `v' at coordinates (`x', `y', `z') in `a'. `x', `y'
and `z' must be within the bounds of `a', as described for
`Genarray.set'; otherwise, `Invalid_arg' is raised.
<<
external sub_left:
('a, 'b, c_layout) t -> pos:int -> len:int -> ('a, 'b, c_layout) t
>>
Extract a three-dimensional sub-array of the given
three-dimensional big array by restricting the first dimension.
See `Genarray.sub_left' for more details. `Array3.sub_left'
applies only to arrays with C layout.
<<
external sub_right:
('a, 'b, fortran_layout) t ->
pos:int -> len:int -> ('a, 'b, fortran_layout) t
>>
Extract a three-dimensional sub-array of the given
three-dimensional big array by restricting the second dimension.
See `Genarray.sub_right' for more details. `Array3.sub_right'
applies only to arrays with Fortran layout.
<<
val slice_left_1:
('a, 'b, c_layout) t -> x:int -> y:int -> ('a, 'b, c_layout) Array1.t
>>
Extract a one-dimensional slice of the given three-dimensional
big array by fixing the first two coordinates. The integer
parameters are the coordinates of the slice to extract. See
`Genarray.slice_left' for more details. `Array3.slice_left_1'
applies only to arrays with C layout.
<<
val slice_right_1:
('a, 'b, fortran_layout) t -> y:int -> z:int ->
('a, 'b, fortran_layout) Array1.t
>>
Extract a one-dimensional slice of the given three-dimensional
big array by fixing the last two coordinates. The integer
parameters are the coordinates of the slice to extract. See
`Genarray.slice_right' for more details. `Array3.slice_right_1'
applies only to arrays with Fortran layout.
<<
val slice_left_2:
('a, 'b, c_layout) t -> x:int -> ('a, 'b, c_layout) Array2.t
>>
Extract a two-dimensional slice of the given three-dimensional
big array by fixing the first coordinate. The integer parameter
is the first coordinate of the slice to extract. See
`Genarray.slice_left' for more details. `Array3.slice_left_2'
applies only to arrays with C layout.
<<
val slice_right_2:
('a, 'b, fortran_layout) t -> z:int -> ('a, 'b, fortran_layout) Array2.t
>>
Extract a two-dimensional slice of the given three-dimensional
big array by fixing the last coordinate. The integer parameter
is the coordinate of the slice to extract. See
`Genarray.slice_right' for more details. `Array3.slice_right_2'
applies only to arrays with Fortran layout.
<<
external blit: src:('a, 'b, 'c) t -> dst:('a, 'b, 'c) t -> unit
>>
Copy the first big array to the second big array. See
`Genarray.blit' for more details.
<<
external fill: ('a, 'b, 'c) t -> 'a -> unit
>>
Fill the given big array with the given value. See
`Genarray.fill' for more details.
<<
val of_array:
kind:('a, 'b) kind -> layout:'c layout ->
'a array array array -> ('a, 'b, 'c) t
>>
Build a three-dimensional big array initialized from the given
array of arrays of arrays.
<<
val map_file: Unix.file_descr -> kind:('a, 'b) kind -> layout:'c layout ->
shared:bool -> dim1:int -> dim2:int -> dim3:int -> ('a, 'b, 'c)
t
>>
Memory mapping of a file as a three-dimensional big array. See
`Genarray.map_file' for more details.
<<
end
>>
Coercions between generic big arrays and fixed-dimension big arrays
====================================================================
<<
val genarray_of_array1: ('a, 'b, 'c) Array1.t -> ('a, 'b, 'c) Genarray.t
val genarray_of_array2: ('a, 'b, 'c) Array2.t -> ('a, 'b, 'c) Genarray.t
val genarray_of_array3: ('a, 'b, 'c) Array3.t -> ('a, 'b, 'c) Genarray.t
>>
Return the generic big array corresponding to the given
one-dimensional, two-dimensional or three-dimensional big array.
<<
val array1_of_genarray: ('a, 'b, 'c) Genarray.t -> ('a, 'b, 'c) Array1.t
>>
Return the one-dimensional big array corresponding to the given
generic big array. Raise `Invalid_arg' if the generic big array
does not have exactly one dimension.
<<
val array2_of_genarray: ('a, 'b, 'c) Genarray.t -> ('a, 'b, 'c) Array2.t
>>
Return the two-dimensional big array corresponding to the given
generic big array. Raise `Invalid_arg' if the generic big array
does not have exactly two dimensions.
<<
val array3_of_genarray: ('a, 'b, 'c) Genarray.t -> ('a, 'b, 'c) Array3.t
>>
Return the three-dimensional big array corresponding to the
given generic big array. Raise `Invalid_arg' if the generic big
array does not have exactly three dimensions.
Re-shaping big arrays
======================
<<
val reshape:
('a, 'b, 'c) Genarray.t -> dims:int array -> ('a, 'b, 'c) Genarray.t
>>
`reshape b [|d1;...;dN|]' converts the big array `b' to a
`N'-dimensional array of dimensions `d1'...`dN'. The returned
array and the original array `b' share their data and have the
same layout. For instance, assuming that `b' is a
one-dimensional array of dimension 12, `reshape b [|3;4|]'
returns a two-dimensional array `b'' of dimensions 3 and 4. If
`b' has C layout, the element `(x,y)' of `b'' corresponds to the
element `x * 3 + y' of `b'. If `b' has Fortran layout, the
element `(x,y)' of `b'' corresponds to the element `x + (y - 1)
* 4' of `b'. The returned big array must have exactly the same
number of elements as the original big array `b'. That is, the
product of the dimensions of `b' must be equal to `i1 * ... *
iN'. Otherwise, `Invalid_arg' is raised.
<<
val reshape_1:
('a, 'b, 'c) Genarray.t -> dim:int -> ('a, 'b, 'c) Array1.t
>>
Specialized version of `reshape' for reshaping to
one-dimensional arrays.
<<
val reshape_2:
('a, 'b, 'c) Genarray.t -> dim1:int -> dim2:int -> ('a, 'b, 'c)
Array2.t
>>
Specialized version of `reshape' for reshaping to
two-dimensional arrays.
<<
val reshape_3:
('a, 'b, 'c) Genarray.t -> dim1:int -> dim2:int -> dim3:int ->
('a, 'b, 'c) Array3.t
>>
Specialized version of `reshape' for reshaping to
three-dimensional arrays.
28.2 Big arrays in the Caml-C interface
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
C stub code that interface C or Fortran code with Caml code, as described in
chapter 17, can exploit big arrays as follows.
28.2.1 Include file
=====================
The include file <caml/bigarray.h> must be included in the C stub file. It
declares the functions, constants and macros discussed below.
28.2.2 Accessing a Caml bigarray from C or Fortran
====================================================
If v is a Caml value representing a big array, the expression
Data_bigarray_val(v) returns a pointer to the data part of the array. This
pointer is of type void * and can be cast to the appropriate C type for the
array (e.g. double [], char [][10], etc).
Various characteristics of the Caml big array can be consulted from C as
follows:
--------------------------------------------------------------------
| C expression | Returns |
--------------------------------------------------------------------
|Bigarray_val(v)->num_dims |number of dimensions |
|Bigarray_val(v)->dim[i[i] |i-th dimension |
|Bigarray_val(v)->flags & BIGARRAY_KIND_MASK|kind of array elements|
--------------------------------------------------------------------
The kind of array elements is one of the following constants:
--------------------------------------------------------------
| Constant | Element kind |
--------------------------------------------------------------
|BIGARRAY_FLOAT32 |32-bit single-precision floats |
|BIGARRAY_FLOAT64 |64-bit double-precision floats |
|BIGARRAY_SINT8 |8-bit signed integers |
|BIGARRAY_UINT8 |8-bit unsigned integers |
|BIGARRAY_SINT16 |16-bit signed integers |
|BIGARRAY_UINT16 |16-bit unsigned integers |
|BIGARRAY_INT32 |32-bit signed integers |
|BIGARRAY_INT64 |64-bit signed integers |
|BIGARRAY_CAML_INT |31- or 63-bit signed integers |
|BIGARRAY_NATIVE_INT|32- or 64-bit (platform-native) integers|
--------------------------------------------------------------
The following example shows the passing of a two-dimensional big array to a
C function and a Fortran function.
<<
extern void my_c_function(double * data, int dimx, int dimy);
extern void my_fortran_function_(double * data, int * dimx, int * dimy);
value caml_stub(value bigarray)
{
int dimx = Bigarray_val(bigarray)->dim[0];
int dimy = Bigarray_val(bigarray)->dim[1];
/* C passes scalar parameters by value */
my_c_function(Data_bigarray_val(bigarray), dimx, dimy);
/* Fortran passes all parameters by reference */
my_fortran_function_(Data_bigarray_val(bigarray), &dimx, &dimy);
return Val_unit;
}
>>
28.2.3 Wrapping a C or Fortran array as a Caml big array
==========================================================
A pointer p to an already-allocated C or Fortran array can be wrapped and
returned to Caml as a big array using the alloc_bigarray or alloc_bigarray_dims
functions.
- alloc_bigarray(kind | layout, numdims, p, dims)
Return a Caml big array wrapping the data pointed to by p. kind is the kind of
array elements (one of the BIGARRAY_ kind constants above). layout is
BIGARRAY_C_LAYOUT for an array with C layout and BIGARRAY_FORTRAN_LAYOUT for
an array with Fortran layout. numdims is the number of dimensions in the
array. dims is an array of numdims long integers, giving the sizes of the
array in each dimension.
- alloc_bigarray_dims(kind | layout, numdims, p, (long) dim_1, (long) dim_2,
..., (long) dim_numdims)
Same as alloc_bigarray, but the sizes of the array in each dimension are
listed as extra arguments in the function call, rather than being passed as
an array.
The following example illustrates how statically-allocated C and Fortran
arrays can be made available to Caml.
<<
extern long my_c_array[100][200];
extern float my_fortran_array_[300][400];
value caml_get_c_array(value unit)
{
long dims[2];
dims[0] = 100; dims[1] = 200;
return alloc_bigarray(BIGARRAY_NATIVEINT | BIGARRAY_C_LAYOUT,
2, my_c_array, dims);
}
value caml_get_fortran_array(value unit)
{
return alloc_bigarray_dims(BIGARRAY_FLOAT32 | BIGARRAY_FORTRAN_LAYOUT,
2, my_fortran_array_, 300L, 400L);
}
>>
Part: V
*******
Appendix
*********
Chapter 29 Index to the library
***********************************
- `!' (operator), 18.1
- `!=' (operator), 18.1
- `&' (operator), 18.1
- `&&' (operator), 18.1
- `*' (operator), 18.1
- `**' (operator), 18.1
- `**/' (operator), 21.1
- `*.' (operator), 18.1
- `*/' (operator), 21.1
- `+' (operator), 18.1
- `+.' (operator), 18.1
- `+/' (operator), 21.1
- `-' (operator), 18.1
- `-.' (operator), 18.1
- `-/' (operator), 21.1
- `/' (operator), 18.1
- `/.' (operator), 18.1
- `//' (operator), 21.1
- `:=' (operator), 18.1
- `<' (operator), 18.1
- `</' (operator), 21.1
- `<=' (operator), 18.1
- `<=/' (operator), 21.1
- `<>' (operator), 18.1
- `<>/' (operator), 21.1
- `=' (operator), 18.1
- `=/' (operator), 21.1
- `==' (operator), 18.1
- `>' (operator), 18.1
- `>/' (operator), 21.1
- `>=' (operator), 18.1
- `>=/' (operator), 21.1
- `@' (operator), 18.1
- `^' (operator), 18.1
- `||' (operator), 18.1
- `~-' (operator), 18.1
- `~-.' (operator), 18.1
- `Arg' (module), 19.1
- `Arith_status' (module), 21.2
- `Array' (module), 19.2
- `Array1' (module), 28.1
- `Array2' (module), 28.1
- `Array3' (module), 28.1
- `Assert_failure' (exception), 7.3, 18.1
- `abs', 18.1, 19.12, 19.13, 19.19
- `abs_float', 18.1
- `abs_num', 21.1
- `accept', 20.1, 23.5
- `access', 20.1
- `acos', 18.1
- `add', 19.11, 19.12, 19.13, 19.19, 19.24, 25.1
- `add_available_units', 26.1
- `add_buffer', 19.3
- `add_channel', 19.3
- `add_char', 19.3
- `add_interfaces', 26.1
- `add_num', 21.1
- `add_string', 19.3
- `add_substring', 19.3
- `alarm', 20.1
- `allocated_bytes', 19.9
- `allow_unsafe_modules', 26.1
- `always', 23.4
- `append', 19.2, 19.16
- `appname_get', 27.1
- `appname_set', 27.1
- `approx_num_exp', 21.1
- `approx_num_fix', 21.1
- `argv', 19.31
- `arith_status', 21.2
- `array', 19.27
- `array1_of_genarray', 28.1
- `array2_of_genarray', 28.1
- `array3_of_genarray', 28.1
- `asin', 18.1
- `asr' (operator), 18.1
- `assoc', 19.16
- `assq', 19.16
- `at_exit', 18.1
- `atan', 18.1
- `atan2', 18.1
- `auto_synchronize', 24.1
- `Bad' (exception), 19.1
- `Bigarray' (module), 28.1
- `Break' (exception), 19.31
- `Buffer' (module), 19.3
- `background', 24.1
- `basename', 19.7
- `big_int_of_num', 21.1
- `bind', 20.1, 27.1
- `bind_class', 27.1
- `bind_tag', 27.1
- `bits', 19.25
- `bits_of_float', 19.13
- `black', 24.1
- `blit', 19.2, 19.30, 19.32
- `blit_image', 24.1
- `blue', 24.1
- `bool_of_string', 18.1
- `bounded_full_split', 22.1
- `bounded_split', 22.1
- `bounded_split_delim', 22.1
- `bprintf', 19.8, 19.23
- `break', 27.1
- `broadcast', 23.3
- `button_down', 24.1
- `Callback' (module), 19.4
- `Char' (module), 19.5
- `Condition' (module), 23.3
- `c_layout', 28.1
- `capitalize', 19.30
- `catch', 19.22
- `catch_break', 19.31
- `ceil', 18.1
- `ceiling_num', 21.1
- `channel', 19.6
- `char', 28.1
- `char_of_int', 18.1
- `chdir', 19.31, 20.1
- `check', 19.32
- `check_suffix', 19.7
- `chmod', 20.1
- `choose', 23.4
- `chop_extension', 19.7
- `chop_suffix', 19.7
- `chown', 20.1
- `chr', 19.5
- `chroot', 20.1
- `classify_float', 18.1
- `clear', 19.3, 19.11, 19.24, 19.28
- `clear_available_units', 26.1
- `clear_close_on_exec', 20.1
- `clear_graph', 24.1
- `clear_nonblock', 20.1
- `clear_parser', 19.21
- `close', 20.1, 25.1
- `close_box', 19.8
- `close_graph', 24.1
- `close_in', 18.1
- `close_out', 18.1
- `close_process', 20.1
- `close_process_full', 20.1
- `close_process_in', 20.1
- `close_process_out', 20.1
- `close_tbox', 19.8
- `closedir', 20.1
- `closeTk', 27.1
- `code', 19.5
- `combine', 19.16
- `command', 19.31
- `compact', 19.9
- `compare', 18.1
- `compare_num', 21.1
- `concat', 19.2, 19.7, 19.16, 19.30
- `connect', 20.1, 23.5
- `contains', 19.30
- `contains_from', 19.30
- `contents', 19.3
- `copy', 19.2, 19.20, 19.30
- `cos', 18.1
- `cosh', 18.1
- `count', 19.29
- `counters', 19.9
- `create', 19.2, 19.3, 19.11, 19.24, 19.28, 19.30, 19.32, 23.1, 23.2, 23.3
- `create_alarm', 19.9
- `create_image', 24.1
- `create_matrix', 19.2
- `create_process', 20.1
- `create_process_env', 20.1
- `current', 19.1
- `current_dir_name', 19.7
- `current_point', 24.1
- `current_x', 24.1
- `current_y', 24.1
- `cyan', 24.1
- `Dbm' (module), 25.1
- `Dbm_error' (exception), 25.1
- `Digest' (module), 19.6
- `Division_by_zero' (exception), 18.1
- `Dynlink' (module), 26.1
- `data_size', 19.18
- `decr', 18.1
- `decr_num', 21.1
- `delay', 23.1
- `delete_alarm', 19.9
- `descr_of_in_channel', 20.1
- `descr_of_out_channel', 20.1
- `destroy', 27.1
- `dirname', 19.7
- `display_mode', 24.1
- `div', 19.12, 19.13, 19.19
- `div_num', 21.1
- `draw_arc', 24.1
- `draw_char', 24.1
- `draw_circle', 24.1
- `draw_ellipse', 24.1
- `draw_image', 24.1
- `draw_rect', 24.1
- `draw_string', 24.1
- `dump_image', 24.1
- `dup', 20.1
- `dup2', 20.1
- `Empty' (exception), 19.24, 19.28
- `End_of_file' (exception), 18.1
- `Error' (exception), 19.29, 26.1
- `Event' (module), 23.4
- `Exit' (exception), 18.1
- `empty', 19.29
- `environment', 20.1
- `eprintf', 19.8, 19.23
- `eq_num', 21.1
- `err_formatter', 19.8
- `error_message', 20.1, 26.1
- `escaped', 19.5, 19.30
- `establish_server', 20.1, 23.5
- `execv', 20.1, 23.5
- `execve', 20.1, 23.5
- `execvp', 20.1, 23.5
- `execvpe', 20.1
- `exists', 19.16
- `exists2', 19.16
- `exit', 18.1, 23.1
- `exp', 18.1
- `Failure' (exception), 18.1, 19.29
- `Filename' (module), 19.7
- `Format' (module), 19.8
- `failwith', 18.1
- `fchmod', 20.1
- `fchown', 20.1
- `file', 19.6
- `file_exists', 19.31
- `fill', 19.2, 19.30, 19.32
- `fill_arc', 24.1
- `fill_circle', 24.1
- `fill_ellipse', 24.1
- `fill_poly', 24.1
- `fill_rect', 24.1
- `filter', 19.16
- `finalise', 19.9
- `find', 19.11, 19.16, 25.1
- `find_all', 19.11, 19.16
- `first_chars', 22.1
- `firstkey', 25.1
- `flatten', 19.16
- `float', 18.1, 19.25
- `float32', 28.1
- `float64', 28.1
- `float_of_bits', 19.13
- `float_of_int', 18.1
- `float_of_num', 21.1
- `float_of_string', 18.1
- `floor', 18.1
- `floor_num', 21.1
- `flush', 18.1
- `flush_str_formatter', 19.8
- `fold_left', 19.2, 19.16
- `fold_left2', 19.16
- `fold_right', 19.2, 19.16
- `fold_right2', 19.16
- `for_all', 19.16
- `for_all2', 19.16
- `force', 7.4, 19.14
- `force_newline', 19.8
- `foreground', 24.1
- `fork', 20.1
- `format', 19.12, 19.13, 19.19
- `formatter_of_buffer', 19.8
- `formatter_of_out_channel', 19.8
- `fortran_layout', 28.1
- `fprintf', 19.8, 19.23
- `frexp', 18.1
- `from', 19.29
- `from_channel', 19.15, 19.18
- `from_function', 19.15
- `from_string', 19.15, 19.18
- `fst', 18.1
- `fstat', 20.1
- `ftruncate', 20.1
- `full_init', 19.25
- `full_major', 19.9
- `full_split', 22.1
- `Gc' (module), 19.9
- `Genarray' (module), 28.1
- `Genlex' (module), 19.10
- `Graphic_failure' (exception), 24.1
- `Graphics' (module), 24.1
- `ge_num', 21.1
- `genarray_of_array1', 28.1
- `genarray_of_array2', 28.1
- `genarray_of_array3', 28.1
- `get', 19.2, 19.9, 19.30, 19.32
- `get_all_formatter_output_functions', 19.8
- `get_approx_printing', 21.2
- `get_copy', 19.32
- `get_ellipsis_text', 19.8
- `get_error_when_null_denominator', 21.2
- `get_floating_precision', 21.2
- `get_formatter_output_functions', 19.8
- `get_image', 24.1
- `get_margin', 19.8
- `get_max_boxes', 19.8
- `get_max_indent', 19.8
- `get_normalize_ratio', 21.2
- `get_normalize_ratio_when_printing', 21.2
- `get_state', 19.25
- `getcwd', 19.31, 20.1
- `getegid', 20.1
- `getenv', 19.31, 20.1
- `geteuid', 20.1
- `getgid', 20.1
- `getgrgid', 20.1
- `getgrnam', 20.1
- `getgroups', 20.1
- `gethostbyaddr', 20.1
- `gethostbyname', 20.1
- `gethostname', 20.1
- `getitimer', 20.1
- `getlogin', 20.1
- `getpeername', 20.1
- `getpid', 20.1
- `getppid', 20.1
- `getprotobyname', 20.1
- `getprotobynumber', 20.1
- `getpwnam', 20.1
- `getpwuid', 20.1
- `getservbyname', 20.1
- `getservbyport', 20.1
- `getsockname', 20.1
- `getsockopt', 20.1
- `gettimeofday', 20.1
- `getuid', 20.1
- `global_replace', 22.1
- `global_substitute', 22.1
- `gmtime', 20.1
- `green', 24.1
- `grid', 27.1
- `group_beginning', 22.1
- `group_end', 22.1
- `gt_num', 21.1
- `guard', 23.4
- `HashedType' (module type), 19.11
- `Hashtbl' (module), 19.11
- `handle_unix_error', 20.1
- `hash', 19.11
- `hash_param', 19.11
- `hd', 19.16
- `header_size', 19.18
- `Int32' (module), 19.12
- `Int64' (module), 19.13
- `Invalid_argument' (exception), 18.1
- `id', 23.1
- `ignore', 18.1
- `in_channel_length', 18.1
- `in_channel_of_descr', 20.1
- `incr', 18.1
- `incr_num', 21.1
- `index', 19.30
- `index_from', 19.30
- `inet_addr_any', 20.1
- `inet_addr_of_string', 20.1
- `infinity', 18.1
- `init', 19.2, 19.25, 26.1
- `input', 18.1, 19.6
- `input_binary_int', 18.1
- `input_byte', 18.1
- `input_char', 18.1
- `input_line', 18.1
- `input_value', 18.1
- `int', 19.25, 28.1
- `int16_signed', 28.1
- `int16_unsigned', 28.1
- `int32', 28.1
- `int64', 28.1
- `int8_signed', 28.1
- `int8_unsigned', 28.1
- `int_of_char', 18.1
- `int_of_float', 18.1
- `int_of_num', 21.1
- `int_of_string', 18.1
- `integer_num', 21.1
- `interactive', 19.31
- `invalid_arg', 18.1
- `is_implicit', 19.7
- `is_integer_num', 21.1
- `is_relative', 19.7
- `iter', 19.2, 19.11, 19.16, 19.24, 19.28, 19.29, 25.1
- `iter2', 19.16
- `iteri', 19.2
- `join', 23.1
- `junk', 19.29
- `key_pressed', 24.1
- `kill', 20.1, 23.1
- `Lazy' (module), 7.4
- `Lazy' (module), 19.14
- `Lexing' (module), 19.15
- `List' (module), 19.16
- `land' (operator), 18.1
- `last_chars', 22.1
- `ldexp', 18.1
- `le_num', 21.1
- `length', 19.2, 19.3, 19.16, 19.24, 19.28, 19.30, 19.32
- `lexeme', 19.15
- `lexeme_char', 19.15
- `lexeme_end', 19.15
- `lexeme_start', 19.15
- `lineto', 24.1
- `link', 20.1
- `list', 19.27
- `listen', 20.1
- `lnot', 18.1
- `loadfile', 26.1
- `loadfile_private', 26.1
- `localtime', 20.1
- `lock', 23.2
- `lockf', 20.1
- `log', 18.1
- `log10', 18.1
- `logand', 19.12, 19.13, 19.19
- `lognot', 19.12, 19.13, 19.19
- `logor', 19.12, 19.13, 19.19
- `logxor', 19.12, 19.13, 19.19
- `lor' (operator), 18.1
- `lower_window', 27.1
- `lowercase', 19.5, 19.30
- `lseek', 20.1
- `lsl' (operator), 18.1
- `lsr' (operator), 18.1
- `lstat', 20.1
- `lt_num', 21.1
- `lxor' (operator), 18.1
- `Make' (functor), 19.11, 19.17, 19.26
- `Map' (module), 19.17
- `Marshal' (module), 19.18
- `Match_failure' (exception), 6.7.1, 6.7.1, 6.7.2, 18.1
- `Mutex' (module), 23.2
- `magenta', 24.1
- `mainLoop', 27.1
- `major', 19.9
- `make', 19.2, 19.30
- `make_formatter', 19.8
- `make_image', 24.1
- `make_lexer', 19.10
- `make_matrix', 19.2
- `map', 19.2, 19.16
- `map2', 19.16
- `mapi', 19.2
- `match_beginning', 22.1
- `match_end', 22.1
- `matched_group', 22.1
- `matched_string', 22.1
- `max', 18.1
- `max_array_length', 19.31
- `max_int', 18.1, 19.12, 19.13, 19.19
- `max_num', 21.1
- `max_string_length', 19.31
- `mem', 19.11, 19.16
- `mem_assoc', 19.16
- `mem_assq', 19.16
- `memq', 19.16
- `merge', 19.27
- `min', 18.1
- `min_int', 18.1, 19.12, 19.13, 19.19
- `min_num', 21.1
- `minor', 19.9
- `minus_num', 21.1
- `minus_one', 19.12, 19.13, 19.19
- `mkdir', 20.1
- `mkfifo', 20.1
- `mktime', 20.1
- `mod' (operator), 18.1
- `mod_float', 18.1
- `mod_num', 21.1
- `modf', 18.1
- `mouse_pos', 24.1
- `moveto', 24.1
- `mul', 19.12, 19.13, 19.19
- `mult_num', 21.1
- `Nativeint' (module), 19.19
- `Not_found' (exception), 18.1
- `Num' (module), 21.1
- `nan', 18.1
- `nat_of_num', 21.1
- `nativeint', 28.1
- `neg', 19.12, 19.13, 19.19
- `neg_infinity', 18.1
- `new_channel', 23.4
- `next', 19.29
- `nextkey', 25.1
- `nice', 20.1
- `not', 18.1
- `npeek', 19.29
- `nth', 19.16
- `num_of_big_int', 21.1
- `num_of_int', 21.1
- `num_of_nat', 21.1
- `num_of_ratio', 21.1
- `num_of_string', 21.1
- `Oo' (module), 19.20
- `OrderedType' (module type), 19.17, 19.26
- `Out_of_memory' (exception), 18.1
- `of_channel', 19.29
- `of_float', 19.12, 19.13, 19.19
- `of_int', 19.12, 19.13, 19.19
- `of_int32', 19.13, 19.19
- `of_list', 19.2, 19.29
- `of_nativeint', 19.13
- `of_string', 19.12, 19.13, 19.19, 19.29
- `one', 19.12, 19.13, 19.19
- `open_box', 19.8
- `open_connection', 20.1, 23.5
- `open_graph', 24.1
- `open_hbox', 19.8
- `open_hovbox', 19.8
- `open_hvbox', 19.8
- `open_in', 18.1
- `open_in_bin', 18.1
- `open_in_gen', 18.1
- `open_out', 18.1
- `open_out_bin', 18.1
- `open_out_gen', 18.1
- `open_process', 20.1, 23.5
- `open_process_full', 20.1, 23.5
- `open_process_in', 20.1, 23.5
- `open_process_out', 20.1, 23.5
- `open_tbox', 19.8
- `open_vbox', 19.8
- `opendbm', 25.1
- `opendir', 20.1
- `openfile', 20.1
- `openTk', 27.1
- `or' (operator), 18.1
- `os_type', 19.31
- `out_channel_length', 18.1
- `out_channel_of_descr', 20.1
- `output', 18.1, 19.6
- `output_binary_int', 18.1
- `output_buffer', 19.3
- `output_byte', 18.1
- `output_char', 18.1
- `output_string', 18.1
- `output_value', 18.1
- `over_max_boxes', 19.8
- `Parse_error' (exception), 19.21
- `Parsing' (module), 19.21
- `Pervasives' (module), 18.1
- `Printexc' (module), 19.22
- `Printf' (module), 19.23
- `pack', 27.1
- `parent_dir_name', 19.7
- `parse', 19.1
- `partition', 19.16
- `pause', 20.1
- `peek', 19.24, 19.29
- `pipe', 20.1, 23.5
- `pixels', 27.1
- `place', 27.1
- `plot', 24.1
- `point_color', 24.1
- `poll', 23.4
- `pop', 19.28
- `pos_in', 18.1
- `pos_out', 18.1
- `power_num', 21.1
- `pp_close_box', 19.8
- `pp_close_tbox', 19.8
- `pp_force_newline', 19.8
- `pp_get_all_formatter_output_functions', 19.8
- `pp_get_ellipsis_text', 19.8
- `pp_get_formatter_output_functions', 19.8
- `pp_get_margin', 19.8
- `pp_get_max_boxes', 19.8
- `pp_get_max_indent', 19.8
- `pp_open_box', 19.8
- `pp_open_hbox', 19.8
- `pp_open_hovbox', 19.8
- `pp_open_hvbox', 19.8
- `pp_open_tbox', 19.8
- `pp_open_vbox', 19.8
- `pp_over_max_boxes', 19.8
- `pp_print_as', 19.8
- `pp_print_bool', 19.8
- `pp_print_break', 19.8
- `pp_print_char', 19.8
- `pp_print_cut', 19.8
- `pp_print_float', 19.8
- `pp_print_flush', 19.8
- `pp_print_if_newline', 19.8
- `pp_print_int', 19.8
- `pp_print_newline', 19.8
- `pp_print_space', 19.8
- `pp_print_string', 19.8
- `pp_print_tab', 19.8
- `pp_print_tbreak', 19.8
- `pp_set_all_formatter_output_functions', 19.8
- `pp_set_ellipsis_text', 19.8
- `pp_set_formatter_out_channel', 19.8
- `pp_set_formatter_output_functions', 19.8
- `pp_set_margin', 19.8
- `pp_set_max_boxes', 19.8
- `pp_set_max_indent', 19.8
- `pp_set_tab', 19.8
- `pred', 18.1, 19.12, 19.13, 19.19
- `pred_num', 21.1
- `prerr_char', 18.1
- `prerr_endline', 18.1
- `prerr_float', 18.1
- `prerr_int', 18.1
- `prerr_newline', 18.1
- `prerr_string', 18.1
- `print', 19.22
- `print_as', 19.8
- `print_bool', 19.8
- `print_break', 19.8
- `print_char', 18.1, 19.8
- `print_cut', 19.8
- `print_endline', 18.1
- `print_float', 18.1, 19.8
- `print_flush', 19.8
- `print_if_newline', 19.8
- `print_int', 18.1, 19.8
- `print_newline', 18.1, 19.8
- `print_space', 19.8
- `print_stat', 19.9
- `print_string', 18.1, 19.8
- `print_tab', 19.8
- `print_tbreak', 19.8
- `printf', 19.8, 19.23
- `push', 19.28
- `putenv', 20.1
- `Queue' (module), 19.24
- `quo_num', 21.1
- `quote', 19.7, 22.1
- `Random' (module), 19.25
- `raise', 18.1
- `raise_window', 27.1
- `ratio_of_num', 21.1
- `rcontains_from', 19.30
- `read', 20.1, 23.5
- `read_float', 18.1
- `read_int', 18.1
- `read_key', 24.1
- `read_line', 18.1
- `readdir', 20.1
- `readlink', 20.1
- `really_input', 18.1
- `receive', 23.4
- `recv', 20.1, 23.5
- `recvfrom', 20.1, 23.5
- `red', 24.1
- `ref', 18.1
- `regexp', 22.1
- `regexp_case_fold', 22.1
- `regexp_string', 22.1
- `regexp_string_case_fold', 22.1
- `register', 19.4
- `register_exception', 19.4
- `rem', 19.12, 19.13, 19.19
- `remember_mode', 24.1
- `remove', 19.11, 19.31, 25.1
- `remove_assoc', 19.16
- `remove_assq', 19.16
- `rename', 19.31, 20.1
- `replace', 19.11, 25.1
- `replace_first', 22.1
- `replace_matched', 22.1
- `reset', 19.3
- `reshape', 28.1
- `reshape_1', 28.1
- `reshape_2', 28.1
- `reshape_3', 28.1
- `rev', 19.16
- `rev_append', 19.16
- `rev_map', 19.16
- `rev_map2', 19.16
- `rewinddir', 20.1
- `rgb', 24.1
- `rhs_end', 19.21
- `rhs_start', 19.21
- `rindex', 19.30
- `rindex_from', 19.30
- `rlineto', 24.1
- `rmdir', 20.1
- `rmoveto', 24.1
- `round_num', 21.1
- `Set' (module), 19.26
- `Sort' (module), 19.27
- `Stack' (module), 19.28
- `Stack_overflow' (exception), 18.1
- `Str' (module), 22.1
- `Stream' (module), 19.29
- `String' (module), 19.30
- `Sys' (module), 19.31
- `Sys_blocked_io' (exception), 18.1
- `Sys_error' (exception), 18.1
- `search_backward', 22.1
- `search_forward', 22.1
- `seek_in', 18.1
- `seek_out', 18.1
- `select', 20.1, 23.1, 23.4, 23.5
- `self', 23.1
- `self_init', 19.25
- `send', 20.1, 23.4, 23.5
- `sendto', 20.1, 23.5
- `set', 19.2, 19.9, 19.30, 19.32
- `set_all_formatter_output_functions', 19.8
- `set_approx_printing', 21.2
- `set_binary_mode_in', 18.1
- `set_binary_mode_out', 18.1
- `set_close_on_exec', 20.1
- `set_color', 24.1
- `set_ellipsis_text', 19.8
- `set_error_when_null_denominator', 21.2
- `set_floating_precision', 21.2
- `set_font', 24.1
- `set_formatter_out_channel', 19.8
- `set_formatter_output_functions', 19.8
- `set_line_width', 24.1
- `set_margin', 19.8
- `set_max_boxes', 19.8
- `set_max_indent', 19.8
- `set_nonblock', 20.1
- `set_normalize_ratio', 21.2
- `set_normalize_ratio_when_printing', 21.2
- `set_signal', 19.31
- `set_state', 19.25
- `set_tab', 19.8
- `set_text_size', 24.1
- `setgid', 20.1
- `setitimer', 20.1
- `setsid', 20.1
- `setsockopt', 20.1
- `setuid', 20.1
- `shift_left', 19.12, 19.13, 19.19
- `shift_right', 19.12, 19.13, 19.19
- `shift_right_logical', 19.12, 19.13, 19.19
- `shutdown', 20.1
- `shutdown_connection', 20.1
- `sigabrt', 19.31
- `sigalrm', 19.31
- `sigchld', 19.31
- `sigcont', 19.31
- `sigfpe', 19.31
- `sighup', 19.31
- `sigill', 19.31
- `sigint', 19.31
- `sigkill', 19.31
- `sign_num', 21.1
- `signal', 19.31, 23.3
- `sigpending', 20.1
- `sigpipe', 19.31
- `sigprocmask', 20.1
- `sigprof', 19.31
- `sigquit', 19.31
- `sigsegv', 19.31
- `sigstop', 19.31
- `sigsuspend', 20.1
- `sigterm', 19.31
- `sigtstp', 19.31
- `sigttin', 19.31
- `sigttou', 19.31
- `sigusr1', 19.31
- `sigusr2', 19.31
- `sigvtalrm', 19.31
- `sin', 18.1
- `sinh', 18.1
- `size', 19.19
- `size_x', 24.1
- `size_y', 24.1
- `sleep', 20.1, 23.5
- `snd', 18.1
- `socket', 20.1, 23.5
- `socketpair', 20.1, 23.5
- `sort', 19.2, 19.16
- `sound', 24.1
- `split', 19.16, 22.1
- `split_delim', 22.1
- `sprintf', 19.8, 19.23
- `sqrt', 18.1
- `square_num', 21.1
- `stable_sort', 19.2, 19.16
- `stat', 19.9, 20.1
- `std_formatter', 19.8
- `stdbuf', 19.8
- `stderr', 18.1, 20.1
- `stdin', 18.1, 20.1
- `stdout', 18.1, 20.1
- `str_formatter', 19.8
- `string', 19.6
- `string_after', 22.1
- `string_before', 22.1
- `string_match', 22.1
- `string_of_bool', 18.1
- `string_of_float', 18.1
- `string_of_inet_addr', 20.1
- `string_of_int', 18.1
- `string_of_num', 21.1
- `string_partial_match', 22.1
- `sub', 19.2, 19.12, 19.13, 19.19, 19.30
- `sub_num', 21.1
- `substitute_first', 22.1
- `substring', 19.6
- `succ', 18.1, 19.12, 19.13, 19.19
- `succ_num', 21.1
- `symbol_end', 19.21
- `symbol_start', 19.21
- `symlink', 20.1
- `sync', 23.4
- `synchronize', 24.1
- `system', 20.1, 23.5
- `Thread' (module), 23.1
- `ThreadUnix' (module), 23.5
- `Tk' (module), 27.1
- `take', 19.24
- `tan', 18.1
- `tanh', 18.1
- `tcdrain', 20.1
- `tcflow', 20.1
- `tcflush', 20.1
- `tcgetattr', 20.1
- `tcsendbreak', 20.1
- `tcsetattr', 20.1
- `temp_file', 19.7
- `text_size', 24.1
- `time', 19.31, 20.1
- `timed_read', 23.5
- `timed_write', 23.5
- `times', 20.1
- `tl', 19.16
- `to_buffer', 19.18
- `to_channel', 19.18
- `to_float', 19.12, 19.13, 19.19
- `to_int', 19.12, 19.13, 19.19
- `to_int32', 19.13, 19.19
- `to_list', 19.2
- `to_nativeint', 19.13
- `to_string', 19.12, 19.13, 19.18, 19.19, 19.22
- `top', 19.28
- `total_size', 19.18
- `transp', 24.1
- `truncate', 18.1, 20.1
- `try_lock', 23.2
- `Undefined' (exception), 19.14
- `Unix' (module), 20.1
- `Unix_error' (exception), 20.1
- `umask', 20.1
- `uncapitalize', 19.30
- `unlink', 20.1
- `unlock', 23.2
- `update', 27.1
- `uppercase', 19.5, 19.30
- `usage', 19.1
- `utimes', 20.1
- `Weak' (module), 19.32
- `wait', 20.1, 23.3, 23.5
- `wait_next_event', 24.1
- `wait_pid', 23.1
- `wait_read', 23.1
- `wait_signal', 23.1
- `wait_timed_read', 23.1
- `wait_timed_write', 23.1
- `wait_write', 23.1
- `waitpid', 20.1, 23.5
- `white', 24.1
- `word_size', 19.31
- `wrap', 23.4
- `wrap_abort', 23.4
- `write', 20.1, 23.5
- `yellow', 24.1
- `yield', 23.1
- `zero', 19.12, 19.13, 19.19
Chapter 30 Index of keywords
********************************
- and, see let, type, class, 6.9.2, 6.9.3, 6.9.4, 6.9.5
- as, 6.4, 6.4, 6.4, 6.6, 6.6, 6.6, 6.9.2, 6.9.2
- assert, 7.3
- begin, 6.7, 6.7.1
- class, 6.9.3, 6.9.4, 6.9.5, 6.10, 6.10.2, 6.10.2, 6.11, 6.11.2, 6.11.2
- constraint, 6.8.1, 6.8.1, 6.9.1, 6.9.1, 6.9.2, 6.9.2
- do, see while, for
- done, see while, for
- downto, see for
- else, see if
- end, 6.7, 6.7.1, 6.9.1, 6.9.2, 6.10, 6.10.2, 6.11, 6.11.2
- exception, 6.8.2, 6.10, 6.10.2, 6.11, 6.11.2
- external, 6.10, 6.10.2, 6.11, 6.11.2
- false, 6.3
- for, 6.7, 6.7.2
- fun, 6.7, 6.7, 6.7.1, 6.9.2
- function, 6.7, 6.7, 6.7.1
- functor, 6.10, 6.10.3, 6.11, 6.11.3
- if, 6.7, 6.7, 6.7.2
- in, see let, 6.9.2
- include, 6.10, 6.10.2, 6.11, 6.11.2
- inherit, 6.9.1, 6.9.1, 6.9.2, 6.9.2
- initializer, 6.9.2, 6.9.2
- lazy, 7.4
- let, 6.7, 6.7, 6.7.1, 6.9.2, 6.11, 6.11.2, 7.6
- match, 6.7, 6.7, 6.7.2, 7.1
- when, 7.1
- method, 6.9.1, 6.9.1, 6.9.1, 6.9.2, 6.9.2, 6.9.2
- module, 6.10, 6.10.2, 6.10.2, 6.11, 6.11.2, 6.11.2, 7.6
- mutable, 6.8.1, 6.8.1, 6.9.1, 6.9.1, 6.9.2, 6.9.2
- new, 6.7, 6.7.5
- not, 6.7
- object, 6.9.1, 6.9.2
- of, see type, exception
- open, 6.10, 6.10.2, 6.11, 6.11.2
- or, 6.7, 6.7, 6.7.2
- parser, 7.1
- private, 6.9.1, 6.9.1, 6.9.1, 6.9.2, 6.9.2, 6.9.2
- rec, see let, 6.9.2
- sig, 6.10, 6.10.2
- struct, 6.11, 6.11.2
- then, see if
- to, see for
- true, 6.3
- try, 6.7, 6.7, 6.7.2
- type, 6.8.1, 6.9.5, 6.10, 6.10.2, 6.10.2, 6.10.2, 6.11, 6.11.2, 6.11.2,
6.11.2
- val, 6.9.1, 6.9.1, 6.9.2, 6.9.2, 6.10, 6.10.2
- virtual, 6.9.1, 6.9.1, 6.9.2, 6.9.2, 6.9.3, 6.9.3, 6.9.4, 6.9.5
- when, 6.7, 6.7.1
- while, 6.7.2
- with, see match, try, 6.10, 6.10.4, 7.5
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