Module CCSeq

Helpers for the standard Seq type

See oseq for a richer API.

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 = Stdlib.Format.formatter -> 'a -> unit

Basics

type +'a t = unit -> 'a node
and +'a node = 'a Stdlib.Seq.node =
| Nil
| Cons of 'a * 'a t
val nil : 'a t
val empty : 'a t
val cons : 'a -> 'a t -> 'a t
val singleton : 'a -> 'a t
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 cycle : 'a t -> 'a t

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

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
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 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 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 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 flat_map : ( 'a -> 'b t ) -> 'a t -> 'b t
val filter_map : ( 'a -> 'b option ) -> 'a t -> 'b t
val flatten : 'a t t -> 'a t
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 at soon as one of them ends.

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 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 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 ",@ ").