ocaml/stdlib/list.mli

124 lines
5.5 KiB
OCaml

(***********************************************************************)
(* *)
(* Caml Special Light *)
(* *)
(* Xavier Leroy, projet Cristal, INRIA Rocquencourt *)
(* *)
(* Copyright 1995 Institut National de Recherche en Informatique et *)
(* Automatique. Distributed only by permission. *)
(* *)
(***********************************************************************)
(* $Id$ *)
(* Module [List]: list operations *)
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 flatten : 'a list list -> 'a list
(* Catenate (flatten) a list of lists. *)
(** Iterators *)
val iter : ('a -> 'b) -> 'a list -> unit
(* [List.iter f [a1; ...; an]] applies function [f] in turn to
[a1; ...; an], discarding all the results. It is equivalent to
[begin f a1; f a2; ...; f an; () end]. *)
val map : ('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]. *)
val fold_left : ('a -> 'b -> 'a) -> 'a -> 'b list -> 'a
(* [List.fold_left f a [b1; ...; bn]] is
[f (... (f (f a b1) b2) ...) bn]. *)
val fold_right : ('a -> 'b -> 'b) -> 'a list -> 'b -> 'b
(* [List.fold_right f [a1; ...; an] b] is
[f a1 (f a2 (... (f an b) ...))]. *)
(** Iterators on two lists *)
val iter2 : ('a -> 'b -> 'c) -> 'a list -> 'b list -> unit
(* [List.iter2 f [a1; ...; an] [b1; ...; bn]] calls in turn
[f a1 b1; ...; f an bn], discarding the results.
Raise [Invalid_argument] if the two lists have
different lengths. *)
val map2 : ('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. *)
val fold_left2 : ('a -> 'b -> 'c -> 'a) -> '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 : ('a -> 'b -> 'c -> 'c) -> 'a list -> 'b list -> '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. *)
(** List scanning *)
val for_all : ('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 : ('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) or (p a2) or ... or (p an)]. *)
val for_all2 : ('a -> 'b -> bool) -> 'a list -> 'b list -> bool
val exists2 : ('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. *)
(** 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 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 assq : 'a -> ('a * 'b) list -> 'b
(* Same as [assoc], but uses physical equality instead of structural
equality to compare keys. *)
(** 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])]
*)
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. *)