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(*
* BatList - additional and modified functions for lists.
* Copyright (C) 2003 Brian Hurt
* Copyright (C) 2003 Nicolas Cannasse
* Copyright (C) 2008 Red Hat Inc.
* Copyright (C) 2009 David Teller, LIFO, Universite d'Orleans
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version,
* with the special exception on linking described in file LICENSE.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*)
(** Additional and modified functions for lists.
The OCaml standard library provides a module for list functions.
This BatList module can be used to extend the List module or
as a standalone module. It provides new functions and modify
the behavior of some other ones (in particular all functions
are now {b tail-recursive}).
The following functions have the same behavior as the [List]
module ones but are tail-recursive: [map], [append], [concat],
[flatten], [fold_right], [remove_assoc], [remove_assq],
[split]. That means they will not
cause a [Stack_overflow] when used on very long list.
The implementation might be a little more slow in bytecode,
but compiling in native code will not affect performances.
This module extends Stdlib's
{{:http://caml.inria.fr/pub/docs/manual-ocaml/libref/List.html}List}
module, go there for documentation on the rest of the functions
and types.
*)
(** List operations.
@documents List
@author Xavier Leroy (base module)
@author Brian Hurt
@author Nicolas Cannasse
@author Richard W.M. Jones
@author David Teller
*)
type 'a t = 'a list
(**The type of lists*)
include BatEnum.Enumerable with type 'a enumerable = 'a t
include BatInterfaces.Mappable with type 'a mappable = 'a t
(**{6 Base operations}*)
val is_empty : 'a list -> bool
(** [is_empty e] returns true if [e] does not contains any element. *)
val cons : 'a -> 'a list -> 'a list
(** [cons h t] returns the list starting with [h] and continuing as [t] *)
val first : 'a list -> 'a
(** Returns the first element of the list, or @raise Empty_list if
the list is empty (similar to [hd]). *)
val hd : 'a list -> 'a
(** Similar to [first], but @raise Failure if the list is empty. *)
val tl : 'a list -> 'a list
(** Return the given list without its first element.
@raise Failure if the list is empty. *)
val last : 'a list -> 'a
(** Returns the last element of the list, or @raise Empty_list if
the list is empty. This function takes linear time. *)
val length : 'a list -> int
(** Return the length (number of elements) of the given list. *)
val at : 'a list -> int -> 'a
(** [at l n] returns the n-th element of the list [l] or
@raise Invalid_argument is the index is outside of [l] bounds. O(l) *)
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 [@].
Tail-recursive O(length of the first argument).*)
val rev_append : 'a list -> 'a list -> 'a list
(** [List.rev_append l1 l2] reverses [l1] and concatenates it to [l2]. *)
val concat : 'a list list -> 'a list
(** Concatenate a list of lists. The elements of the argument are all
concatenated together (in the same order) to give the result.
Tail-recursive
(length of the argument + length of the longest sub-list). *)
val flatten : 'a list list -> 'a list
(** Same as [concat]. *)
(**{6 Constructors}*)
val make : int -> 'a -> 'a list
(** Similar to [String.make], [make n x] returns a
list containing [n] elements [x]. *)
val init : int -> (int -> 'a) -> 'a list
(** Similar to [Array.init], [init n f] returns the list containing
the results of (f 0),(f 1).... (f (n-1)).
@raise Invalid_argument if n < 0.*)
(**{6 Iterators}*)
val iter : ('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 iteri : (int -> 'a -> unit) -> 'a list -> unit
(** [iteri f l] will call [(f 0 a0);(f 1 a1) ... (f n an)] where
[a0..an] are the elements of the list [l]. *)
val map : ('a -> 'b) -> 'a list -> 'b list
(** [map f [a0; a1; ...; an]] applies function [f] to [a0, a1, ..., an],
and builds the list [[f a0; f a1; ...; f an]]
with the results returned by [f]. Tail-recursive. *)
(* why that formulation emphasizing "applies function f to
..." ? Because map is specifically designed to respect
a left-to-right order of evaluation *)
val rev_map : ('a -> 'b) -> 'a list -> 'b list
(** [List.rev_map f l] gives the same result as
{!List.rev}[ (]{!List.map}[ f l)]. *)
val mapi : (int -> 'a -> 'b) -> 'a list -> 'b list
(** [mapi f l] will build the list containing
[(f 0 a0);(f 1 a1) ... (f n an)] where [a0..an] are the elements of
the list [l]. *)
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 [a0; a1; ...; an] b] is
[f a0 (f a1 (... (f an b) ...))]. Tail-recursive. *)
val reduce : ('a -> 'a -> 'a) -> 'a list -> 'a
(** [List.reduce f h::t] is [fold_left f h t].
@raise Empty_list on empty lists. *)
val max : 'a list -> 'a
(** [max l] returns the largest value in [l] as judged by
[Pervasives.compare] *)
val min : 'a list -> 'a
(** [min l] returns the smallest value in [l] as judged by
[Pervasives.compare] *)
val sum : int list -> int
(** [sum l] returns the sum of the integers of [l] *)
val fsum : float list -> float
(** [fsum l] returns the sum of the floats of [l] *)
(** {6 Iterators on two lists} *)
val iter2 : ('a -> 'b -> unit) -> 'a list -> 'b list -> unit
(** [List.iter2 f [a0; a1; ...; an] [b0; b1; ...; bn]] calls in turn
[f a0 b0; f a1 b1; ...; f an bn].
@raise Different_list_size if the two lists have
different lengths. *)
val map2 : ('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
(** [List.map2 f [a0; a1; ...; an] [b0; b1; ...; bn]] is
[[f a0 b0; f a1 b1; ...; f an bn]].
@raise Different_list_size if the two lists have
different lengths. Tail-recursive. *)
val rev_map2 : ('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
(** [List.rev_map2 f l1 l2] gives the same result as
{!List.rev}[ (]{!List.map2}[ f l1 l2)], but is tail-recursive and
more efficient. *)
val fold_left2 : ('a -> 'b -> 'c -> 'a) -> 'a -> 'b list -> 'c list -> 'a
(** [List.fold_left2 f a [b0; b1; ...; bn] [c0; c1; ...; cn]] is
[f (... (f (f a b0 c0) b1 c1) ...) bn cn].
@raise Different_list_size if the two lists have
different lengths. *)
val fold_right2 : ('a -> 'b -> 'c -> 'c) -> 'a list -> 'b list -> 'c -> 'c
(** [List.fold_right2 f [a0; a1; ...; an] [b0; b1; ...; bn] c] is
[f a0 b0 (f a1 b1 (... (f an bn c) ...))].
@raise Different_list_size if the two lists have
different lengths. Tail-recursive. *)
(**{6 List scanning}*)
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 {!List.mem}, but uses physical equality instead of structural
equality to compare list elements. *)
(**{7 Unary predicate, One list}*)
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) || (p a2) || ... || (p an)]. *)
(**{7 Binary predicate, Two lists}*)
val for_all2 : ('a -> 'b -> bool) -> 'a list -> 'b list -> bool
(** Same as {!List.for_all}, but for a two-argument predicate.
@raise Invalid_argument if the two lists have
different lengths. *)
val exists2 : ('a -> 'b -> bool) -> 'a list -> 'b list -> bool
(** Same as {!List.exists}, but for a two-argument predicate.
@raise Invalid_argument if the two lists have
different lengths. *)
(**{6 List searching}*)
val find : ('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 find_exn : ('a -> bool) -> exn -> 'a list -> 'a
(** [find_exn p e l] returns the first element of [l] such as [p x]
returns [true] or raises [e] if such an element has not been found. *)
val findi : (int -> 'a -> bool) -> 'a list -> (int * 'a)
(** [findi p e l] returns the first element [ai] of [l] along with its
index [i] such that [p i ai] is true, or @raise Not_found if no
such element has been found. *)
val find_map : ('a -> 'b option) -> 'a list -> 'b
(** [find_map pred list] finds the first element of [list] for which
[pred element] returns [Some r]. It returns [r] immediately
once found or @raise Not_found if no element matches the
predicate. See also {!filter_map}. *)
val rfind : ('a -> bool) -> 'a list -> 'a
(** [rfind p l] returns the last element [x] of [l] such as [p x] returns
[true] or @raise Not_found if such element as not been found. *)
val filter : ('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. *)
val filter_map : ('a -> 'b option) -> 'a list -> 'b list
(** [filter_map f l] calls [(f a0) (f a1).... (f an)] where [a0,a1..an] are
the elements of [l]. It returns the list of elements [bi] such as
[f ai = Some bi] (when [f] returns [None], the corresponding element of
[l] is discarded). *)
val find_all : ('a -> bool) -> 'a list -> 'a list
(** [find_all] is another name for {!List.filter}. *)
val partition : ('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. *)
val index_of : 'a -> 'a list -> int option
(** [index_of e l] returns the index of the first occurrence of [e]
in [l], or [None] if there is no occurrence of [e] in [l] *)
val index_ofq : 'a -> 'a list -> int option
(** [index_ofq e l] behaves as [index_of e l] except it uses
physical equality*)
val rindex_of : 'a -> 'a list -> int option
(** [rindex_of e l] returns the index of the last occurrence of [e]
in [l], or [None] if there is no occurrence of [e] in [l] *)
val rindex_ofq : 'a -> 'a list -> int option
(** [rindex_ofq e l] behaves as [rindex_of e l] except it uses
physical equality*)
val unique : ?eq:('a -> 'a -> bool) -> 'a list -> 'a list
(** [unique cmp l] returns the list [l] without any duplicate element.
The default comparator ( = ) is used if no comparison function
specified.
Implementation Note: The current implementation removes any
elements where the tail of the list contains an equal element,
thus it keeps the *last* copy of each equal element.
This function takes O(n^2) time.
@see 'sort_unique' to save time in cases when reordering the list is
acceptable
@since 2.0
*)
val unique_cmp : ?cmp:('a -> 'a -> int) -> 'a list -> 'a list
(** As [unique], except comparator parameter returns an int. Default
comparator is [Pervasives.compare]. This function takes O(n log n)
time.
Implementation Note: The current implementation removes subsequent
elements that compare as equal to earlier elements in the list,
thus it keeps the *first* copy of each equal element.
@since 1.3.0 *)
val unique_hash : ?hash:('a -> int) -> ?eq:('a -> 'a -> bool) -> 'a list -> 'a list
(** As [unique], except uses a hash table to cut down the expected
runtime to linear, assuming a good hash function. [?hash]
defaults to [Hashtbl.hash] and [?eq] defaults to [(=)].
Implementation Note: The current implementation removes subsequent
elements that hash and compare as equal to earlier elements in the
list, thus it keeps the *first* copy of each equal element.
@since 2.0.0
*)
(**{6 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 assoc_inv : 'b -> ('a * 'b) list -> 'a
(** [assoc_inv b l] returns the key associated with value [b] in the list of
pairs [l]. That is, [assoc b [ ...; (a,b); ...] = a]
if [(a,b)] is the leftmost binding of [a] in list [l].
@raise Not_found if there is no key associated with [b] in the
list [l]. *)
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.
Tail-recursive. *)
val mem_assoc : 'a -> ('a * 'b) list -> bool
(** Same as {!List.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 {!List.assoc}, but uses physical equality instead of structural
equality to compare keys. *)
val assq_inv : 'b -> ('a * 'b) list -> 'a
(** Same as {!List.assoc_inv}, but uses physical equality instead of structural
equality to compare keys. *)
val remove_assq : 'a -> ('a * 'b) list -> ('a * 'b) list
(** Same as {!List.remove_assoc}, but uses physical equality instead
of structural equality to compare keys. Tail-recursive. *)
val mem_assq : 'a -> ('a * 'b) list -> bool
(** Same as {!List.mem_assoc}, but uses physical equality instead of
structural equality to compare keys. *)
(** {6 List transformations}*)
val split_at : int -> 'a list -> 'a list * 'a list
(** [split_at n l] returns two lists [l1] and [l2], [l1] containing the
first [n] elements of [l] and [l2] the others. @raise Invalid_argument if
[n] is outside of [l] size bounds. *)
val split_nth : int -> 'a list -> 'a list * 'a list
(** Obsolete. As [split_at]. *)
val remove : 'a list -> 'a -> 'a list
(** [remove l x] returns the list [l] without the first element [x] found
or returns [l] if no element is equal to [x]. Elements are compared
using ( = ). *)
val remove_if : ('a -> bool) -> 'a list -> 'a list
(** [remove_if cmp l] is similar to [remove], but with [cmp] used
instead of ( = ). *)
val remove_all : 'a list -> 'a -> 'a list
(** [remove_all l x] is similar to [remove] but removes all elements that
are equal to [x] and not only the first one. *)
val take : int -> 'a list -> 'a list
(** [take n l] returns up to the [n] first elements from list [l], if
available. *)
val drop : int -> 'a list -> 'a list
(** [drop n l] returns [l] without the first [n] elements, or the empty
list if [l] have less than [n] elements. *)
val take_while : ('a -> bool) -> 'a list -> 'a list
(** [take_while p xs] returns the (possibly empty) longest prefix of
elements of [xs] that satisfy the predicate [p].*)
val drop_while : ('a -> bool) -> 'a list -> 'a list
(** [drop_while p xs] returns the suffix remaining after
[takeWhile p xs]. *)
val interleave : ?first:'a -> ?last:'a -> 'a -> 'a list -> 'a list
(** [interleave ~first ~last sep [a0;a1;a2;...;an]] returns
[first; a0; sep; a1; sep; a2; sep; ...; sep; an; last] *)
(** {6 BatEnum functions}
Abstraction layer.*)
val enum : 'a list -> 'a BatEnum.t
(** Returns an enumeration of the elements of a list. This enumeration may
be used to visit elements of the list in forward order (i.e. from the
first element to the last one)*)
val of_enum : 'a BatEnum.t -> 'a list
(** Build a list from an enumeration. In the result, elements appear in the
same order as they did in the source enumeration. *)
val backwards : 'a list -> 'a BatEnum.t
(** Returns an enumeration of the elements of a list. This enumeration may
be used to visit elements of the list in backwards order (i.e. from the
last element to the first one)*)
val of_backwards : 'a BatEnum.t -> 'a list
(** Build a list from an enumeration. The first element of the enumeration
becomes the last element of the list, the second element of the
enumeration
becomes the second-to-last element of the list... *)
(** {6 List of pairs}*)
val split : ('a * 'b) list -> 'a list * 'b list
(** Transform a list of pairs into a pair of lists:
[split [(a0,b0); (a1,b1); ...; (an,bn)]] is [([a0; a1; ...; an], [b0;
b1; ...; bn])].
Tail-recursive.
*)
val combine : 'a list -> 'b list -> ('a * 'b) list
(** Transform a pair of lists into a list of pairs:
[combine [a0; a1; ...; an] [b0; b1; ...; bn]] is
[[(a0,b0); (a1,b1); ...; (an,bn)]].
@raise Different_list_size if the two lists
have different lengths. Tail-recursive. *)
(** {6 Sorting}*)
val sort : ('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 its arguments
compare as equal, a positive integer if the first is greater,
and a negative integer if the first is smaller (see Array.sort for
a complete specification). For example,
{!Pervasives.compare} 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. It runs in constant
heap space and logarithmic stack space.
*)
val stable_sort : ('a -> 'a -> int) -> 'a list -> 'a list
(** Same as {!List.sort}, but the sorting algorithm is guaranteed to
be stable (i.e. elements that compare equal are kept in their
original order) .
The current implementation uses Merge Sort. It runs in constant
heap space and logarithmic stack space.
*)
val fast_sort : ('a -> 'a -> int) -> 'a list -> 'a list
(** Same as {!List.sort} or {!List.stable_sort}, whichever is faster
on typical input. *)
val merge : ('a -> 'a -> int) -> 'a list -> 'a list -> 'a list
(** Merge two lists:
Assuming that [l1] and [l2] are sorted according to the
comparison function [cmp], [merge cmp l1 l2] will return a
sorted list containting all the elements of [l1] and [l2].
If several elements compare equal, the elements of [l1] will be
before the elements of [l2].
Not tail-recursive (sum of the lengths of the arguments).
*)
val sort_unique : ('a -> 'a -> int) -> 'a list -> 'a list
(** [sort_unique cmp l] returns the list [l] sorted and without any duplicate
element. [cmp] is a usual comparison function providing total order.
This function takes O(n log n) time.
*)
(** {6 Utilities}*)
val group : ('a -> 'a -> int) -> 'a list -> 'a list list
(** [group cmp l] returns list of groups and each group consists of
elements judged equal by comparison function [cmp]. Groups in the resulting
list appear in order given by [cmp]. All groups are always nonempty. [group]
returns [[]] only if [l] is empty.
For example [group cmp [f;c;b;e;d;a]] can give [[[a;b];[c];[d;e;f]]] if
following conditions are met:
[cmp a b = 0], [cmp b c = -1], [cmp c d = -1], [cmp d e = 0],...
*)
val cartesian_product : 'a list -> 'b list -> ('a * 'b) list
(** Different from [List.combine], this returns every pair
of elements formed out of the two lists.
[cartesian_product [a0; a1; ...; an] [b0; b1; ...; bn] =
[(a0,b0);(a0,b1); ...; (a0,bn); (a1,b0); ..; (a1, bn);
...; (an,bn)]]. The lists can be of unequal size. *)
val n_cartesian_product : 'a list list -> 'a list list
(** Given n lists, return the n-way cartesian product of
these lists. Given [[a;b];[c];[d;e;f]], returns
[[a;c;d];[a;c;e];[a;c;f];[b;c;d];[b;c;e];[b;c;f]], all
ways of choosing one element from each input list. *)
val transpose : 'a list list -> 'a list list
(** Transposes a list of lists, turning rows of the input into columns
of the output and vice versa.
@since 2.0.0
*)
(** {6 Boilerplate code}*)
(** {7 Printing}*)
val print : ?first:string -> ?last:string -> ?sep:string -> ('a
BatInnerIO.output -> 'b -> unit) -> 'a BatInnerIO.output -> 'b list -> unit
(**Print the contents of a list*)
open BatOrd
val eq : 'a eq -> 'a list eq
val ord : 'a ord -> 'a list ord
val compare : 'a comp -> 'a list comp
(** Comparison and equality for lists based on element comparison and
equality *)
module Eq (T : Eq) : Eq with type t = T.t list
module Ord (T : Ord) : Ord with type t = T.t list
module Comp (T : Comp) : Comp with type t = T.t list
(** {6 Obsolete functions} *)
val nth : 'a list -> int -> 'a
(** Obsolete. As [at]. *)
val takewhile : ('a -> bool) -> 'a list -> 'a list
(** obsolete, as {!take_while} *)
val dropwhile : ('a -> bool) -> 'a list -> 'a list
(** obsolete, as {!drop_while} *)
(** {6 Override modules}*)
(**
The following modules replace functions defined in {!List} with functions
behaving slightly differently but having the same name. This is by
design:
the functions meant to override the corresponding functions of {!List}.
*)
(** Exceptionless counterparts for error-raising operations*)
module Exceptionless : sig
val find : ('a -> bool) -> 'a list -> 'a option
(** [find p l] returns [Some x] where [x] is the first element
of [l] such as [p x] returns [true] or [None] if such an
element has not been found.*)
val rfind : ('a -> bool) -> 'a list -> 'a option
(** [rfind p l] returns [Some x] where [x] is the last element of [l]
such
that [p x] returns [true] or [None] if such element as not been found. *)
val findi : (int -> 'a -> bool) -> 'a list -> (int * 'a) option
(** [findi p e l] returns [Some (i, ai)] where [ai] and [i] are
respectively the
first element of [l] and its index, such that [p i ai] is true,
or [None] if no such element has been found. *)
val split_at : int -> 'a list -> [`Ok of ('a list * 'a list) |
`Invalid_argument of string]
(** Whenever [n] is inside of [l] size bounds, [split_at n l] returns
[Ok(l1,l2)], where [l1] contains the first [n] elements of [l] and [l2]
contains the others. Otherwise, returns [`Invalid_argument n] *)
val at : 'a list -> int -> [`Ok of 'a | `Invalid_argument of string]
(** If [n] is inside the bounds of [l], [at l n] returns [Ok x], where
[x] is the n-th element of the list [l]. Otherwise, returns [Error
(`Invalid_argument(n))].*)
val assoc : 'a -> ('a * 'b) list -> 'b option
(** [assoc a l] returns [Some b] where [b] is the value associated with
key [b]
in the list of pairs [l]. That is, [assoc a [ ...; (a,b); ...] = Some b]
if [(a,b)] is the leftmost binding of [a] in list [l].
Return [None] if there is no value associated with [a] in the
list [l]. *)
val assoc_inv : 'b -> ('a * 'b) list -> 'a option
(** [assoc_inv b l] returns [Some a] where [a] is the key associated with
value [b]
in the list of pairs [l]. That is, [assoc b [ ...; (a,b); ...] = Some a]
if [(a,b)] is the leftmost binding of [a] in list [l].
Return [None] if there is no key associated with [b] in the
list [l]. *)
val assq : 'a -> ('a * 'b) list -> 'b option
(** As {!assoc} but with physical equality. *)
val find_map : ('a -> 'b option) -> 'a list -> 'b option
(** [find_map f xs] returns [Some y] such that [x] is the first
element of the list where [f x] returns [Some y]. It returns [None]
if no such element exists. *)
val hd : ('a list -> 'a option)
(** [hd l] returns [Some x] such that [x] is the first element of the given
list [l].
Returns [None] if list [l] is empty. *)
val tl : ('a list -> 'a list option)
(** [tl l] returns [Some x] such that [x] is the given list [l] without its
first element.
Returns [None] if list [l] is empty *)
val last : 'a list -> 'a option
(** [last l] returns either [Some x] where [x] is the last element of the list, or [None] if
the list is empty. This function takes linear time. *)
end
(** {6 Infix submodule regrouping all infix operators} *)
module Infix : sig
val ( @ ) : 'a list -> 'a list -> 'a list
end
(** Operations on {!List} with labels.
This module overrides a number of functions of {!List} by
functions in which some arguments require labels. These labels are
there to improve readability and safety and to let you change the
order of arguments to functions. In every case, the behavior of the
function is identical to that of the corresponding function of {!List}.
*)
module Labels : sig
val init : int -> f:(int -> 'a) -> 'a list
val iter : f:('a -> unit) -> 'a list -> unit
val iteri : f:(int -> 'a -> unit) -> 'a list -> unit
val map : f:('a -> 'b) -> 'a list -> 'b list
val mapi : f:(int -> 'a -> 'b) -> 'a list -> 'b list
val rev_map : f:('a -> 'b) -> 'a list -> 'b list
val fold_left : f:('a -> 'b -> 'a) -> init:'a -> 'b list -> 'a
val fold_right : f:('a -> 'b -> 'b) -> 'a list -> init:'b -> 'b
val iter2 : f:('a -> 'b -> unit) -> 'a list -> 'b list -> unit
val map2 : f:('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
val rev_map2 : f:('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
val fold_left2 : f:('a -> 'b -> 'c -> 'a) -> init:'a -> 'b list -> 'c list -> 'a
val fold_right2 : f:('a -> 'b -> 'c -> 'c) -> 'a list -> 'b list -> init:'c -> 'c
val for_all : f:('a -> bool) -> 'a list -> bool
val exists : f:('a -> bool) -> 'a list -> bool
val for_all2 : f:('a -> 'b -> bool) -> 'a list -> 'b list -> bool
val exists2 : f:('a -> 'b -> bool) -> 'a list -> 'b list -> bool
val find : f:('a -> bool) -> 'a list -> 'a
val find_exn : f:('a -> bool) -> exn -> 'a list -> 'a
val findi : f:(int -> 'a -> bool) -> 'a list -> (int * 'a)
val rfind : f:('a -> bool) -> 'a list -> 'a
val filter : f:('a -> bool) -> 'a list -> 'a list
val filter_map : f:('a -> 'b option) -> 'a list -> 'b list
val find_all : f:('a -> bool) -> 'a list -> 'a list
val partition : f:('a -> bool) -> 'a list -> 'a list * 'a list
val remove_if : f:('a -> bool) -> 'a list -> 'a list
val take_while : f:('a -> bool) -> 'a list -> 'a list
val drop_while : f:('a -> bool) -> 'a list -> 'a list
val stable_sort : ?cmp:('a -> 'a -> int) -> 'a list -> 'a list
val fast_sort : ?cmp:('a -> 'a -> int) -> 'a list -> 'a list
val merge : ?cmp:('a -> 'a -> int) -> 'a list -> 'a list -> 'a list
module LExceptionless : sig
val find : f:('a -> bool) -> 'a list -> 'a option
val rfind : f:('a -> bool) -> 'a list -> 'a option
val findi : f:(int -> 'a -> bool) -> 'a list -> (int * 'a) option
val split_at : int -> 'a list ->
[`Ok of ('a list * 'a list) |`Invalid_argument of string]
val at : 'a list -> int -> [`Ok of 'a | `Invalid_argument of string]
val assoc : 'a -> ('a * 'b) list -> 'b option
val assoc_inv : 'b -> ('a * 'b) list -> 'a option
val assq : 'a -> ('a * 'b) list -> 'b option
end
end
val ( @ ) : 'a list -> 'a list -> 'a list
(** Tail recursive [List.append]. *)
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