CCSeq (u.313963eda8ee4be42095ea3bc154b4f0.containers.3.15.doc.containers.CCSeq)

type 'a iter = ('a -> unit) -> unit

type 'a gen = unit -> 'a option

type 'a equal = 'a -> 'a -> bool

type 'a ord = 'a -> 'a -> int

type 'a printer = Format.formatter -> 'a -> unit

Basics

Functional Iterators

The type 'a t is a delayed list, i.e. a list where some evaluation is needed to access the next element. This makes it possible to build infinite sequences, to build sequences as we traverse them, and to transform them in a lazy fashion rather than upfront.

since 4.07

type 'a t = unit -> 'a node

The type of delayed lists containing elements of type 'a. Note that the concrete list node 'a node is delayed under a closure, not a lazy block, which means it might be recomputed every time we access it.

and +'a node =

| Nil
| Cons of 'a * 'a t
(*
A fully-evaluated list node, either empty or containing an element and a delayed tail.
*)

val nil : 'a t

val empty : 'a t

val cons : 'a -> 'a t -> 'a t

val singleton : 'a -> 'a t

val init : int -> (int -> 'a) -> 'a t

init n f corresponds to the sequence f 0; f 1; ...; f (n-1).

raises Invalid_argument
if n is negative.

since 3.10

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

repeat ~n x repeats x n times then stops. If n is omitted, then x is repeated forever.

val forever : (unit -> 'a) -> 'a t

forever f corresponds to the infinite sequence containing all the f ().

since 3.10

val cycle : 'a t -> 'a t

Cycle through the iterator infinitely. The iterator shouldn't be empty.

val iterate : ('a -> 'a) -> 'a -> 'a t

iterate f a corresponds to the infinite sequence containing a, f a, f (f a), ...

since 3.10

val unfold : ('b -> ('a * 'b) option) -> 'b -> 'a t

unfold f acc calls f acc and:

if f acc = Some (x, acc'), yield x, continue with unfold f acc'.
if f acc = None, stops.

val is_empty : 'a t -> bool

is_empty xs checks in the sequence xs is empty

val head : 'a t -> 'a option

Head of the list.

val head_exn : 'a t -> 'a

Unsafe version of head.

raises Not_found
if the list is empty.

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

Tail of the list.

val tail_exn : 'a t -> 'a t

Unsafe version of tail.

raises Not_found
if the list is empty.

val uncons : 'a t -> ('a * 'a t) option

uncons xs return None if xs is empty other

since 3.10

val equal : 'a equal -> 'a t equal

Equality step by step. Eager.

val compare : 'a ord -> 'a t ord

Lexicographic comparison. Eager.

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

Fold on values.

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

Alias for fold

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

fold_lefti f init xs applies f acc i x where acc is the result of the previous computation or init for the first one, i is the index in the sequence (starts at 0) and x is the element of the sequence.

since 3.10

val fold_lefti : ('a -> int -> 'b -> 'a) -> 'a -> 'b t -> 'a

Alias of foldi.

since 3.10

val iter : ('a -> unit) -> 'a t -> unit

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

Iterate with index (starts at 0).

val length : _ t -> int

Number of elements in the list. Will not terminate if the list if infinite: use (for instance) take to make the list finite if necessary.

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

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

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

val drop_while : ('a -> bool) -> 'a t -> 'a t

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

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

Map with index (starts at 0).

val fmap : ('a -> 'b option) -> 'a t -> 'b t

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

val append : 'a t -> 'a t -> 'a t

val product_with : ('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t

Fair product of two (possibly infinite) lists into a new list. Lazy. The first parameter is used to combine each pair of elements.

val map_product : ('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t

Alias of product_with.

since 3.10

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

Specialization of product_with producing tuples.

val group : 'a equal -> 'a t -> 'a t t

group eq l groups together consecutive elements that satisfy eq. Lazy. For instance group (=) [1;1;1;2;2;3;3;1] yields [1;1;1]; [2;2]; [3;3]; [1].

val uniq : 'a equal -> 'a t -> 'a t

uniq eq l returns l but removes consecutive duplicates. Lazy. In other words, if several values that are equal follow one another, only the first of them is kept.

val for_all : ('a -> bool) -> 'a t -> bool

for_all p [a1; ...; an] checks if all elements of the sequence satisfy the predicate p. That is, it returns (p a1) && ... && (p an) for a non-empty list and true if the sequence is empty. It consumes the sequence until it finds an element not satisfying the predicate.

since 3.3

val exists : ('a -> bool) -> 'a t -> bool

exists p [a1; ...; an] checks if at least one element of the sequence satisfies the predicate p. That is, it returns (p a1) || ... || (p an) for a non-empty sequence and false if the list is empty. It consumes the sequence until it finds an element satisfying the predicate.

since 3.3

val find : ('a -> bool) -> 'a t -> 'a option

find p [a1; ...; an] return Some ai for the first ai satisfying the predicate p and return None otherwise.

since 3.10

val find_map : ('a -> 'b option) -> 'a t -> 'b option

find f [a1; ...; an] return Some (f ai) for the first ai such that f ai = Some _ and return None otherwise.

since 3.10

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

scan f init xs is the sequence containing the intermediate result of fold f init xs.

since 3.10

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

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

Alias of flat_map

since 3.10

val filter_map : ('a -> 'b option) -> 'a t -> 'b t

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

val concat : 'a t t -> 'a t

Alias of flatten.

since 3.10

val range : int -> int -> int t

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

a -- b is the range of integers containing a and b (therefore, never empty).

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

a -- b is the integer range from a to b, where b is excluded.

Operations on two Collections

val fold2 : ('acc -> 'a -> 'b -> 'acc) -> 'acc -> 'a t -> 'b t -> 'acc

Fold on two collections at once. Stop as soon as one of them ends.

val fold_left2 : ('acc -> 'a -> 'b -> 'acc) -> 'acc -> 'a t -> 'b t -> 'acc

Alias for fold2.

since 3.10

val map2 : ('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t

Map on two collections at once. Stop as soon as one of the arguments is exhausted.

val iter2 : ('a -> 'b -> unit) -> 'a t -> 'b t -> unit

Iterate on two collections at once. Stop as soon as one of them ends.

val for_all2 : ('a -> 'b -> bool) -> 'a t -> 'b t -> bool

val exists2 : ('a -> 'b -> bool) -> 'a t -> 'b t -> bool

val merge : 'a ord -> 'a t -> 'a t -> 'a t

Merge two sorted iterators into a sorted iterator.

val sorted_merge : 'a ord -> 'a t -> 'a t -> 'a t

Alias of merge.

since 3.10

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

Combine elements pairwise. Stop as soon as one of the lists stops.

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

Split each tuple in the list.

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

Alias of unzip.

since 3.10

val zip_i : 'a t -> (int * 'a) t

zip_i seq zips the index of each element with the element itself.

since 3.8

Misc

val sort : cmp:'a ord -> 'a t -> 'a t

Eager sort. Require the iterator to be finite. O(n ln(n)) time and space.

val sort_uniq : cmp:'a ord -> 'a t -> 'a t

Eager sort that removes duplicate values. Require the iterator to be finite. O(n ln(n)) time and space.

val memoize : 'a t -> 'a t

Avoid recomputations by caching intermediate results.

Fair Combinations

val interleave : 'a t -> 'a t -> 'a t

Fair interleaving of both streams.

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

Fair version of flat_map.

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

Fair version of (<*>).

Implementations

val return : 'a -> 'a t

val pure : 'a -> 'a t

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

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

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

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

Infix version of fair_flat_map.

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

Infix version of fair_app.

Infix operators

module Infix : sig ... end

module type MONAD = sig ... end

module Traverse (M : MONAD) : sig ... end

Conversions

val of_list : 'a list -> 'a t

val to_list : 'a t -> 'a list

Gather all values into a list.

val of_array : 'a array -> 'a t

Iterate on the array.

val to_array : 'a t -> 'a array

Convert into array.

val to_rev_list : 'a t -> 'a list

Convert to a list, in reverse order. More efficient than to_list.

val to_iter : 'a t -> 'a iter

val to_gen : 'a t -> 'a gen

val of_gen : 'a gen -> 'a t

of_gen g consumes the generator and caches intermediate results.

val of_string : string -> char t

Iterate on characters.

since 3.7

IO

val pp : 
  ?pp_start:unit printer ->
  ?pp_stop:unit printer ->
  ?pp_sep:unit printer ->
  'a printer ->
  'a t printer

pp ~pp_start ~pp_stop ~pp_sep pp_item ppf s formats the sequence s on ppf. Each element is formatted with pp_item, pp_start is called at the beginning, pp_stop is called at the end, pp_sep is called between each elements. By defaults pp_start and pp_stop does nothing and pp_sep defaults to (fun out -> Format.fprintf out ",@ ").