package containers

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package containers
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Complements to list

include module type of ListLabels
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 compare_lengths : 'a list -> 'b list -> int

Compare the lengths of two lists. compare_lengths l1 l2 is equivalent to compare (length l1) (length l2), except that the computation stops after itering on the shortest list.

  • since 4.05.0
val compare_length_with : 'a list -> len:int -> int

Compare the length of a list to an integer. compare_length_with l n is equivalent to compare (length l) n, except that the computation stops after at most n iterations on the list.

  • since 4.05.0
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. Raise Invalid_argument "List.nth" if n is negative.

val nth_opt : 'a list -> int -> 'a option

Return the n-th element of the given list. The first element (head of the list) is at position 0. Return None if the list is too short. Raise Invalid_argument "List.nth" if n is negative.

  • since 4.05
val rev : 'a list -> 'a list

List reversal.

val rev_append : 'a list -> 'a list -> 'a list

List.rev_append l1 l2 reverses l1 and concatenates it with 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

Concatenate a list of lists. The elements of the argument are all concatenated together (in the same order) to give the result. 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 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.

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 are determined to 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 are determined to have different lengths. Not tail-recursive.

val rev_map2 : f:('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 : 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 are determined to 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 are determined to 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

Same as List.for_all, but for a two-argument predicate. Raise Invalid_argument if the two lists are determined to have different lengths.

val exists2 : f:('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 are determined to have different lengths.

val memq : 'a -> set:'a list -> bool

Same as List.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 find_opt : f:('a -> bool) -> 'a list -> 'a option

find p l returns the first element of the list l that satisfies the predicate p. Returns None if there is no value that satisfies p in the list l.

  • since 4.05
val find_all : f:('a -> bool) -> 'a list -> 'a list

find_all is another name for List.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 assq : 'a -> ('a * 'b) list -> 'b

Same as List.assoc, but uses physical equality instead of structural equality to compare keys.

val mem_assq : 'a -> map:('a * 'b) list -> bool

Same as List.mem_assoc, 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. 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 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 : cmp:('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 : cmp:('a -> 'a -> int) -> 'a list -> 'a list

Same as List.sort or List.stable_sort, whichever is faster on typical input.

val merge : cmp:('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 containing 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).

Iterators
type 'a t = 'a list
val empty : 'a t

empty is .

val is_empty : _ t -> bool

is_empty l returns true iff l = [].

  • since 0.11
val map : f:('a -> 'b) -> 'a t -> 'b t

Safe version of List.map.

val (>|=) : 'a t -> ('a -> 'b) -> 'b t

Infix version of map with reversed arguments.

  • since 0.5
val cons : 'a -> 'a t -> 'a t

cons x l is x::l.

  • since 0.12
val append : 'a t -> 'a t -> 'a t

Safe version of List.append. Concatenate two lists.

val cons_maybe : 'a option -> 'a t -> 'a t

cons_maybe (Some x) l is x :: l. cons_maybe None l is l.

  • since 0.13
val (@) : 'a t -> 'a t -> 'a t

Like append. Concatenate two lists.

val filter : f:('a -> bool) -> 'a t -> 'a t

Safe version of List.filter. 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 fold_right : ('a -> 'b -> 'b) -> 'a t -> 'b -> 'b

Safe version of fold_right. fold_right f [a1; ...; an] b is f a1 (f a2 (... (f an b) ...)). Not tail-recursive.

val fold_while : f:('a -> 'b -> 'a * [ `Stop | `Continue ]) -> init:'a -> 'b t -> 'a

Fold until a stop condition via ('a, `Stop) is indicated by the accumulator.

  • since 0.8
val fold_map : f:('acc -> 'a -> 'acc * 'b) -> init:'acc -> 'a list -> 'acc * 'b list

fold_map ~f ~init l is a fold_left-like function, but it also maps the list to another list.

  • since 0.14
val fold_map2 : f:('acc -> 'a -> 'b -> 'acc * 'c) -> init:'acc -> 'a list -> 'b list -> 'acc * 'c list

fold_map2 is to fold_map what List.map2 is to List.map.

  • raises Invalid_argument

    if the lists do not have the same length.

  • since 0.16
val fold_filter_map : f:('acc -> 'a -> 'acc * 'b option) -> init:'acc -> 'a list -> 'acc * 'b list

fold_filter_map ~f ~init l is a fold_left-like function, but also generates a list of output in a way similar to filter_map.

  • since 0.17
val fold_flat_map : f:('acc -> 'a -> 'acc * 'b list) -> init:'acc -> 'a list -> 'acc * 'b list

fold_flat_map f acc l is a fold_left-like function, but it also maps the list to a list of lists that is then flatten'd.

  • since 0.14
val init : int -> f:(int -> 'a) -> 'a t

init len ~f is f 0; f 1; ...; f (len-1).

  • raises Invalid_argument

    if len < 0.

  • since 0.6
val compare : ('a -> 'a -> int) -> 'a t -> 'a t -> int
val equal : ('a -> 'a -> bool) -> 'a t -> 'a t -> bool
val flat_map : f:('a -> 'b t) -> 'a t -> 'b t

Map and flatten at the same time (safe). Evaluation order is not guaranteed.

val flatten : 'a t t -> 'a t

Safe flatten. Concatenate a list of lists.

val product : f:('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t

Cartesian product of the two lists, with the given combinator.

val fold_product : f:('c -> 'a -> 'b -> 'c) -> init:'c -> 'a t -> 'b t -> 'c

Fold on the cartesian product.

val diagonal : 'a t -> ('a * 'a) t

All pairs of distinct positions of the list. list_diagonal l will return the list of List.nth i l, List.nth j l if i < j.

val partition_map : f:('a -> [< `Left of 'b | `Right of 'c | `Drop ]) -> 'a list -> 'b list * 'c list

partition_map ~f l maps f on l and gather results in lists:

  • if f x = `Left y, adds y to the first list.
  • if f x = `Right z, adds z to the second list.
  • if f x = `Drop, ignores x.
  • since 0.11
val sublists_of_len : ?last:('a list -> 'a list option) -> ?offset:int -> len:int -> 'a list -> 'a list list

sublists_of_len n l returns sub-lists of l that have length n. By default, these sub-lists are non overlapping: sublists_of_len 2 [1;2;3;4;5;6] returns [1;2]; [3;4]; [5;6].

See CCList.sublists_of_len for more details.

  • since 1.5
val pure : 'a -> 'a t

pure is return.

val (<*>) : ('a -> 'b) t -> 'a t -> 'b t

funs <*> l is product fun f x -> f x) funs l.

val (<$>) : ('a -> 'b) -> 'a t -> 'b t

(<$>) is map.

val return : 'a -> 'a t

return x is x.

val (>>=) : 'a t -> ('a -> 'b t) -> 'b t

l >>= f is flat_map f l.

val take : int -> 'a t -> 'a t

Take the n first elements, drop the rest.

val drop : int -> 'a t -> 'a t

Drop the n first elements, keep the rest.

val hd_tl : 'a t -> 'a * 'a t

hd_tl (x :: l) returns hd, l.

  • raises Failure

    if the list is empty.

  • since 0.16
val take_drop : int -> 'a t -> 'a t * 'a t

take_drop n l returns l1, l2 such that l1 @ l2 = l and length l1 = min (length l) n.

val take_while : f:('a -> bool) -> 'a t -> 'a t

take_while ~f l returns the longest prefix of l for which f is true.

  • since 0.13
val drop_while : f:('a -> bool) -> 'a t -> 'a t

drop_while ~f l drops the longest prefix of l for which f is true.

  • since 0.13
val last : int -> 'a t -> 'a t

last n l takes the last n elements of l (or less if l doesn't have that many elements.

val head_opt : 'a t -> 'a option

First element.

  • since 0.20
val tail_opt : 'a t -> 'a t option

Return the given list without its first element.

  • since 2.0
val last_opt : 'a t -> 'a option

Last element.

  • since 0.20
val find_pred : f:('a -> bool) -> 'a t -> 'a option

find_pred p l finds the first element of l that satisfies p, or returns None if no element satisfies p.

  • since 0.11
val find_pred_exn : f:('a -> bool) -> 'a t -> 'a

Unsafe version of find_pred.

  • raises Not_found

    if no such element is found.

  • since 0.11
val find_map : f:('a -> 'b option) -> 'a t -> 'b option

find_map ~f l traverses l, applying f to each element. If for some element x, f x = Some y, then Some y is returned. Otherwise the call returns None.

  • since 0.11
val find_mapi : f:(int -> 'a -> 'b option) -> 'a t -> 'b option

Like find_map, but also pass the index to the predicate function.

  • since 0.11
val find_idx : f:('a -> bool) -> 'a t -> (int * 'a) option

find_idx p x returns Some (i,x) where x is the i-th element of l, and p x holds. Otherwise returns None.

val remove : eq:('a -> 'a -> bool) -> key:'a -> 'a t -> 'a t

remove ~key l removes every instance of key from l. Tail-recursive.

  • parameter eq

    equality function.

  • since 0.11
val filter_map : f:('a -> 'b option) -> 'a t -> 'b t

filter_map ~f l is the sublist of l containing only elements for which f returns Some e. Map and remove elements at the same time.

val sorted_merge : cmp:('a -> 'a -> int) -> 'a list -> 'a list -> 'a list

Merges elements from both sorted list.

val sort_uniq : cmp:('a -> 'a -> int) -> 'a list -> 'a list

Sort the list and remove duplicate elements.

val sorted_merge_uniq : cmp:('a -> 'a -> int) -> 'a list -> 'a list -> 'a list

sorted_merge_uniq l1 l2 merges the sorted lists l1 and l2 and removes duplicates.

  • since 0.10
val is_sorted : cmp:('a -> 'a -> int) -> 'a list -> bool

is_sorted l returns true iff l is sorted (according to given order).

  • parameter cmp

    the comparison function (default Pervasives.compare).

  • since 0.17
val sorted_insert : cmp:('a -> 'a -> int) -> ?uniq:bool -> 'a -> 'a list -> 'a list

sorted_insert x l inserts x into l such that, if l was sorted, then sorted_insert x l is sorted too.

  • parameter uniq

    if true and x is already in sorted position in l, then x is not duplicated. Default false (x will be inserted in any case).

  • since 0.17
val uniq_succ : eq:('a -> 'a -> bool) -> 'a list -> 'a list

uniq_succ l removes duplicate elements that occur one next to the other. Examples: uniq_succ [1;2;1] = [1;2;1]. uniq_succ [1;1;2] = [1;2].

  • since 0.10
val group_succ : eq:('a -> 'a -> bool) -> 'a list -> 'a list list

group_succ ~eq l groups together consecutive elements that are equal according to eq.

  • since 0.11

Indices

val mapi : f:(int -> 'a -> 'b) -> 'a t -> 'b t

Like map, but the function is applied to the index of the element as first argument (counting from 0), and the element itself as second argument.

val iteri : f:(int -> 'a -> unit) -> 'a t -> unit

Like iter, but the function is applied to the index of the element as first argument (counting from 0), and the element itself as second argument.

val foldi : f:('b -> int -> 'a -> 'b) -> init:'b -> 'a t -> 'b

Like fold but it also passes in the index of each element to the folded function. Tail-recursive.

val get_at_idx : int -> 'a t -> 'a option

Get by index in the list. If the index is negative, it will get element starting from the end of the list.

val get_at_idx_exn : int -> 'a t -> 'a

Get the i-th element, or

  • raises Not_found

    if the index is invalid. If the index is negative, it will get element starting from the end of the list.

val set_at_idx : int -> 'a -> 'a t -> 'a t

Set i-th element (removes the old one), or does nothing if index is too high. If the index is negative, it will set element starting from the end of the list.

val insert_at_idx : int -> 'a -> 'a t -> 'a t

Insert at i-th position, between the two existing elements. If the index is too high, append at the end of the list. If the index is negative, it will insert element starting from the end of the list.

val remove_at_idx : int -> 'a t -> 'a t

Remove element at given index. Does nothing if the index is too high. If the index is negative, it will remove element starting from the end of the list.

Set Operators

Those operations maintain the invariant that the list does not contain duplicates (if it already satisfies it).

val add_nodup : eq:('a -> 'a -> bool) -> 'a -> 'a t -> 'a t

add_nodup x set adds x to set if it was not already present. Linear time.

  • since 0.11
val remove_one : eq:('a -> 'a -> bool) -> 'a -> 'a t -> 'a t

remove_one x set removes one occurrence of x from set. Linear time.

  • since 0.11
val mem : eq:('a -> 'a -> bool) -> 'a -> 'a t -> bool

Membership to the list. Linear time.

val subset : eq:('a -> 'a -> bool) -> 'a t -> 'a t -> bool

Test for inclusion.

val uniq : eq:('a -> 'a -> bool) -> 'a t -> 'a t

Remove duplicates w.r.t the equality predicate. Complexity is quadratic in the length of the list, but the order of elements is preserved. If you wish for a faster de-duplication but do not care about the order, use sort_uniq.

val union : eq:('a -> 'a -> bool) -> 'a t -> 'a t -> 'a t

List union. Complexity is product of length of inputs.

val inter : eq:('a -> 'a -> bool) -> 'a t -> 'a t -> 'a t

List intersection. Complexity is product of length of inputs.

Other Constructors

val range_by : step:int -> int -> int -> int t

range_by ~step i j iterates on integers from i to j included, where the difference between successive elements is step. use a negative step for a decreasing list.

  • raises Invalid_argument

    if step=0.

  • since 0.18
val range : int -> int -> int t

range i j iterates on integers from i to j included. It works both for decreasing and increasing ranges.

val range' : int -> int -> int t

Like range but the second bound is excluded. For instance range' 0 5 = [0;1;2;3;4].

val (--) : int -> int -> int t

Infix alias for range.

val (--^) : int -> int -> int t

Infix alias for range'.

  • since 0.17
val replicate : int -> 'a -> 'a t

Replicate the given element n times.

val repeat : int -> 'a t -> 'a t

Concatenate the list with itself n times.

Association Lists

module Assoc : sig ... end
val assoc : eq:('a -> 'a -> bool) -> 'a -> ('a * 'b) t -> 'b

Like Assoc.get_exn.

  • since 2.0
val assoc_opt : eq:('a -> 'a -> bool) -> 'a -> ('a * 'b) t -> 'b option

Like Assoc.get.

  • since 2.0
val assq_opt : 'a -> ('a * 'b) t -> 'b option

Safe version of assq.

  • since 2.0
val mem_assoc : eq:('a -> 'a -> bool) -> 'a -> ('a * _) t -> bool

Like Assoc.mem.

  • since 2.0
val remove_assoc : eq:('a -> 'a -> bool) -> 'a -> ('a * 'b) t -> ('a * 'b) t

Like Assoc.remove.

  • since 2.0

References on Lists

  • since 0.3.3
module Ref : sig ... end
module type MONAD = sig ... end
module Traverse (M : MONAD) : sig ... end

Conversions

type 'a sequence = ('a -> unit) -> unit
type 'a gen = unit -> 'a option
type 'a klist = unit -> [ `Nil | `Cons of 'a * 'a klist ]
type 'a printer = Format.formatter -> 'a -> unit
type 'a random_gen = Random.State.t -> 'a
val random : 'a random_gen -> 'a t random_gen
val random_non_empty : 'a random_gen -> 'a t random_gen
val random_len : int -> 'a random_gen -> 'a t random_gen
val random_choose : 'a t -> 'a random_gen

Randomly choose an element in the list.

  • raises Not_found

    if the list is empty.

val random_sequence : 'a random_gen t -> 'a t random_gen
val to_seq : 'a t -> 'a sequence

Return a sequence of the elements of the list.

val of_seq : 'a sequence -> 'a t

Build a list from a given sequence.

val to_gen : 'a t -> 'a gen

Return a gen of the elements of the list.

val of_gen : 'a gen -> 'a t

Build a list from a given gen.

val to_klist : 'a t -> 'a klist

Return a klist of the elements of the list.

val of_klist : 'a klist -> 'a t

Build a list from a given klist.

Infix Operators

It is convenient to openCCList.Infix to access the infix operators without cluttering the scope too much.

  • since 0.16
module Infix : sig ... end

IO

val pp : ?start:string -> ?stop:string -> ?sep:string -> 'a printer -> 'a t printer

Print the contents of a list.

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