NAME

       Seq - Sequences (functional iterators).

Module

       Module   Seq

Documentation

       Module Seq
        : sig end

       Sequences (functional iterators).

       The  type  'a  Seq.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.

       type 'a node =
        | Nil
        | Cons of 'a * 'a t

       A fully-evaluated list node, either empty or containing an element and a delayed tail.

       val empty : 'a t

       The empty sequence, containing no elements.

       val return : 'a -> 'a t

       The singleton sequence containing only the given element.

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

       cons x xs is the sequence containing the element x followed by the sequence xs

       Since 4.11

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

       append xs ys is the sequence xs followed by the sequence ys

       Since 4.11

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

       map f seq returns a new sequence whose elements are the elements of  seq  ,  transformed  by  f  .   This
       transformation is lazy, it only applies when the result is traversed.

       If seq = [1;2;3] , then map f seq = [f 1; f 2; f 3] .

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

       Remove  from  the  sequence the elements that do not satisfy the given predicate.  This transformation is
       lazy, it only applies when the result is traversed.

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

       Apply the function to every element; if f x = None then x is dropped; if f x = Some y then y is returned.
       This transformation is lazy, it only applies when the result is traversed.

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

       concatenate a sequence of sequences.

       Since 4.13

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

       Map each element to a subsequence,  then  return  each  element  of  this  sub-sequence  in  turn.   This
       transformation is lazy, it only applies when the result is traversed.

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

       Alias for Seq.flat_map .

       Since 4.13

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

       Traverse  the  sequence  from  left to right, combining each element with the accumulator using the given
       function.  The traversal happens immediately and will not terminate on infinite sequences.

       Also see List.fold_left

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

       Iterate on the sequence, calling the (imperative) function  on  every  element.   The  traversal  happens
       immediately and will not terminate on infinite sequences.

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

       Build a sequence from a step function and an initial value.  unfold f u returns empty if f u returns None
       , or fun () -> Cons (x, unfold f y) if f u returns Some (x, y) .

       For example, unfold (function [] -> None | h::t -> Some (h,t)) l is equivalent to List.to_seq l .

       Since 4.11

OCamldoc                                           2022-01-24                                            Seq(3o)