364 lines
13 KiB
OCaml
364 lines
13 KiB
OCaml
(**************************************************************************)
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(* *)
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(* OCaml *)
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(* *)
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(* Xavier Leroy, projet Cristal, INRIA Rocquencourt *)
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(* *)
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(* Copyright 1996 Institut National de Recherche en Informatique et *)
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(* en Automatique. *)
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(* *)
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(* All rights reserved. This file is distributed under the terms of *)
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(* the GNU Lesser General Public License version 2.1, with the *)
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(* special exception on linking described in the file LICENSE. *)
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(* *)
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(**************************************************************************)
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(** List operations.
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Some functions are flagged as not tail-recursive. A tail-recursive
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function uses constant stack space, while a non-tail-recursive function
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uses stack space proportional to the length of its list argument, which
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can be a problem with very long lists. When the function takes several
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list arguments, an approximate formula giving stack usage (in some
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unspecified constant unit) is shown in parentheses.
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The above considerations can usually be ignored if your lists are not
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longer than about 10000 elements.
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*)
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val length : 'a list -> int
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(** Return the length (number of elements) of the given list. *)
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val hd : 'a list -> 'a
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(** Return the first element of the given list. Raise
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[Failure "hd"] if the list is empty. *)
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val compare_lengths : 'a list -> 'b list -> int
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(** Compare the lengths of two lists. [compare_lengths l1 l2] is
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equivalent to [compare (length l1) (length l2)], except that
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the computation stops after itering on the shortest list.
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@since 4.05.0
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*)
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val compare_length_with : 'a list -> len:int -> int
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(** Compare the length of a list to an integer. [compare_length_with l n] is
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equivalent to [compare (length l) n], except that
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the computation stops after at most [n] iterations on the list.
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@since 4.05.0
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*)
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val cons : 'a -> 'a list -> 'a list
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(** [cons x xs] is [x :: xs]
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@since 4.05.0
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*)
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val tl : 'a list -> 'a list
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(** Return the given list without its first element. Raise
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[Failure "tl"] if the list is empty. *)
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val nth : 'a list -> int -> 'a
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(** Return the [n]-th element of the given list.
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The first element (head of the list) is at position 0.
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Raise [Failure "nth"] if the list is too short.
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Raise [Invalid_argument "List.nth"] if [n] is negative. *)
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val nth_opt: 'a list -> int -> 'a option
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(** Return the [n]-th element of the given list.
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The first element (head of the list) is at position 0.
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Return [None] if the list is too short.
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Raise [Invalid_argument "List.nth"] if [n] is negative.
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@since 4.05
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*)
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val rev : 'a list -> 'a list
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(** List reversal. *)
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val init : len:int -> f:(int -> 'a) -> 'a list
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(** [List.init len f] is [f 0; f 1; ...; f (len-1)], evaluated left to right.
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@raise Invalid_argument if [len < 0].
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@since 4.06.0
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*)
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val append : 'a list -> 'a list -> 'a list
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(** Catenate two lists. Same function as the infix operator [@].
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Not tail-recursive (length of the first argument). The [@]
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operator is not tail-recursive either. *)
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val rev_append : 'a list -> 'a list -> 'a list
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(** [List.rev_append l1 l2] reverses [l1] and concatenates it with [l2].
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This is equivalent to [(]{!List.rev}[ l1) @ l2], but [rev_append] is
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tail-recursive and more efficient. *)
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val concat : 'a list list -> 'a list
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(** Concatenate a list of lists. The elements of the argument are all
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concatenated together (in the same order) to give the result.
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Not tail-recursive
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(length of the argument + length of the longest sub-list). *)
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val flatten : 'a list list -> 'a list
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(** Same as [concat]. Not tail-recursive
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(length of the argument + length of the longest sub-list). *)
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(** {1 Iterators} *)
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val iter : f:('a -> unit) -> 'a list -> unit
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(** [List.iter f [a1; ...; an]] applies function [f] in turn to
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[a1; ...; an]. It is equivalent to
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[begin f a1; f a2; ...; f an; () end]. *)
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val iteri : f:(int -> 'a -> unit) -> 'a list -> unit
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(** Same as {!List.iter}, but the function is applied to the index of
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the element as first argument (counting from 0), and the element
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itself as second argument.
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@since 4.00.0
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*)
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val map : f:('a -> 'b) -> 'a list -> 'b list
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(** [List.map f [a1; ...; an]] applies function [f] to [a1, ..., an],
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and builds the list [[f a1; ...; f an]]
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with the results returned by [f]. Not tail-recursive. *)
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val mapi : f:(int -> 'a -> 'b) -> 'a list -> 'b list
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(** Same as {!List.map}, but the function is applied to the index of
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the element as first argument (counting from 0), and the element
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itself as second argument.
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@since 4.00.0
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*)
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val rev_map : f:('a -> 'b) -> 'a list -> 'b list
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(** [List.rev_map f l] gives the same result as
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{!List.rev}[ (]{!List.map}[ f l)], but is tail-recursive and
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more efficient. *)
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val fold_left : f:('a -> 'b -> 'a) -> init:'a -> 'b list -> 'a
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(** [List.fold_left f a [b1; ...; bn]] is
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[f (... (f (f a b1) b2) ...) bn]. *)
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val fold_right : f:('a -> 'b -> 'b) -> 'a list -> init:'b -> 'b
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(** [List.fold_right f [a1; ...; an] b] is
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[f a1 (f a2 (... (f an b) ...))]. Not tail-recursive. *)
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(** {1 Iterators on two lists} *)
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val iter2 : f:('a -> 'b -> unit) -> 'a list -> 'b list -> unit
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(** [List.iter2 f [a1; ...; an] [b1; ...; bn]] calls in turn
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[f a1 b1; ...; f an bn].
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Raise [Invalid_argument] if the two lists are determined
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to have different lengths. *)
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val map2 : f:('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
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(** [List.map2 f [a1; ...; an] [b1; ...; bn]] is
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[[f a1 b1; ...; f an bn]].
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Raise [Invalid_argument] if the two lists are determined
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to have different lengths. Not tail-recursive. *)
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val rev_map2 : f:('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
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(** [List.rev_map2 f l1 l2] gives the same result as
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{!List.rev}[ (]{!List.map2}[ f l1 l2)], but is tail-recursive and
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more efficient. *)
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val fold_left2 :
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f:('a -> 'b -> 'c -> 'a) -> init:'a -> 'b list -> 'c list -> 'a
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(** [List.fold_left2 f a [b1; ...; bn] [c1; ...; cn]] is
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[f (... (f (f a b1 c1) b2 c2) ...) bn cn].
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Raise [Invalid_argument] if the two lists are determined
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to have different lengths. *)
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val fold_right2 :
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f:('a -> 'b -> 'c -> 'c) -> 'a list -> 'b list -> init:'c -> 'c
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(** [List.fold_right2 f [a1; ...; an] [b1; ...; bn] c] is
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[f a1 b1 (f a2 b2 (... (f an bn c) ...))].
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Raise [Invalid_argument] if the two lists are determined
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to have different lengths. Not tail-recursive. *)
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(** {1 List scanning} *)
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val for_all : f:('a -> bool) -> 'a list -> bool
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(** [for_all p [a1; ...; an]] checks if all elements of the list
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satisfy the predicate [p]. That is, it returns
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[(p a1) && (p a2) && ... && (p an)]. *)
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val exists : f:('a -> bool) -> 'a list -> bool
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(** [exists p [a1; ...; an]] checks if at least one element of
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the list satisfies the predicate [p]. That is, it returns
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[(p a1) || (p a2) || ... || (p an)]. *)
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val for_all2 : f:('a -> 'b -> bool) -> 'a list -> 'b list -> bool
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(** Same as {!List.for_all}, but for a two-argument predicate.
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Raise [Invalid_argument] if the two lists are determined
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to have different lengths. *)
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val exists2 : f:('a -> 'b -> bool) -> 'a list -> 'b list -> bool
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(** Same as {!List.exists}, but for a two-argument predicate.
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Raise [Invalid_argument] if the two lists are determined
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to have different lengths. *)
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val mem : 'a -> set:'a list -> bool
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(** [mem a l] is true if and only if [a] is equal
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to an element of [l]. *)
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val memq : 'a -> set:'a list -> bool
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(** Same as {!List.mem}, but uses physical equality instead of structural
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equality to compare list elements. *)
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(** {1 List searching} *)
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val find : f:('a -> bool) -> 'a list -> 'a
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(** [find p l] returns the first element of the list [l]
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that satisfies the predicate [p].
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Raise [Not_found] if there is no value that satisfies [p] in the
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list [l]. *)
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val find_opt: f:('a -> bool) -> 'a list -> 'a option
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(** [find p l] returns the first element of the list [l]
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that satisfies the predicate [p].
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Returns [None] if there is no value that satisfies [p] in the
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list [l].
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@since 4.05 *)
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val filter : f:('a -> bool) -> 'a list -> 'a list
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(** [filter p l] returns all the elements of the list [l]
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that satisfy the predicate [p]. The order of the elements
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in the input list is preserved. *)
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val find_all : f:('a -> bool) -> 'a list -> 'a list
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(** [find_all] is another name for {!List.filter}. *)
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val partition : f:('a -> bool) -> 'a list -> 'a list * 'a list
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(** [partition p l] returns a pair of lists [(l1, l2)], where
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[l1] is the list of all the elements of [l] that
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satisfy the predicate [p], and [l2] is the list of all the
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elements of [l] that do not satisfy [p].
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The order of the elements in the input list is preserved. *)
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(** {1 Association lists} *)
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val assoc : 'a -> ('a * 'b) list -> 'b
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(** [assoc a l] returns the value associated with key [a] in the list of
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pairs [l]. That is,
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[assoc a [ ...; (a,b); ...] = b]
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if [(a,b)] is the leftmost binding of [a] in list [l].
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Raise [Not_found] if there is no value associated with [a] in the
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list [l]. *)
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val assoc_opt: 'a -> ('a * 'b) list -> 'b option
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(** [assoc_opt a l] returns the value associated with key [a] in the list of
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pairs [l]. That is,
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[assoc a [ ...; (a,b); ...] = b]
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if [(a,b)] is the leftmost binding of [a] in list [l].
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Returns [None] if there is no value associated with [a] in the
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list [l].
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@since 4.05
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*)
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val assq : 'a -> ('a * 'b) list -> 'b
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(** Same as {!List.assoc}, but uses physical equality instead of
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structural equality to compare keys. *)
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val assq_opt: 'a -> ('a * 'b) list -> 'b option
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(** Same as {!List.assoc_opt}, but uses physical equality instead of
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structural equality to compare keys.
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@since 4.05.0 *)
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val mem_assoc : 'a -> map:('a * 'b) list -> bool
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(** Same as {!List.assoc}, but simply return true if a binding exists,
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and false if no bindings exist for the given key. *)
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val mem_assq : 'a -> map:('a * 'b) list -> bool
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(** Same as {!List.mem_assoc}, but uses physical equality instead of
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structural equality to compare keys. *)
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val remove_assoc : 'a -> ('a * 'b) list -> ('a * 'b) list
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(** [remove_assoc a l] returns the list of
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pairs [l] without the first pair with key [a], if any.
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Not tail-recursive. *)
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val remove_assq : 'a -> ('a * 'b) list -> ('a * 'b) list
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(** Same as {!List.remove_assoc}, but uses physical equality instead
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of structural equality to compare keys. Not tail-recursive. *)
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(** {1 Lists of pairs} *)
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val split : ('a * 'b) list -> 'a list * 'b list
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(** Transform a list of pairs into a pair of lists:
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[split [(a1,b1); ...; (an,bn)]] is [([a1; ...; an], [b1; ...; bn])].
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Not tail-recursive.
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*)
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val combine : 'a list -> 'b list -> ('a * 'b) list
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(** Transform a pair of lists into a list of pairs:
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[combine [a1; ...; an] [b1; ...; bn]] is
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[[(a1,b1); ...; (an,bn)]].
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Raise [Invalid_argument] if the two lists
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have different lengths. Not tail-recursive. *)
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(** {1 Sorting} *)
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val sort : cmp:('a -> 'a -> int) -> 'a list -> 'a list
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(** Sort a list in increasing order according to a comparison
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function. The comparison function must return 0 if its arguments
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compare as equal, a positive integer if the first is greater,
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and a negative integer if the first is smaller (see Array.sort for
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a complete specification). For example,
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{!Stdlib.compare} is a suitable comparison function.
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The resulting list is sorted in increasing order.
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[List.sort] is guaranteed to run in constant heap space
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(in addition to the size of the result list) and logarithmic
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stack space.
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The current implementation uses Merge Sort. It runs in constant
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heap space and logarithmic stack space.
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*)
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val stable_sort : cmp:('a -> 'a -> int) -> 'a list -> 'a list
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(** Same as {!List.sort}, but the sorting algorithm is guaranteed to
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be stable (i.e. elements that compare equal are kept in their
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original order) .
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The current implementation uses Merge Sort. It runs in constant
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heap space and logarithmic stack space.
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*)
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val fast_sort : cmp:('a -> 'a -> int) -> 'a list -> 'a list
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(** Same as {!List.sort} or {!List.stable_sort}, whichever is
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faster on typical input. *)
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val sort_uniq : cmp:('a -> 'a -> int) -> 'a list -> 'a list
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(** Same as {!List.sort}, but also remove duplicates.
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@since 4.03.0 *)
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val merge : cmp:('a -> 'a -> int) -> 'a list -> 'a list -> 'a list
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(** Merge two lists:
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Assuming that [l1] and [l2] are sorted according to the
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comparison function [cmp], [merge cmp l1 l2] will return a
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sorted list containing all the elements of [l1] and [l2].
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If several elements compare equal, the elements of [l1] will be
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before the elements of [l2].
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Not tail-recursive (sum of the lengths of the arguments).
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*)
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(** {6 Iterators} *)
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val to_seq : 'a list -> 'a Seq.t
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(** Iterate on the list
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@since 4.07 *)
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val of_seq : 'a Seq.t -> 'a list
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(** Create a list from the iterator
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@since 4.07 *)
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