lwd/lib/lwd/lwd_utils.mli

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OCaml

type 'a monoid = 'a * ('a -> 'a -> 'a)
(** A monoid, defined by a default element and an associative operation *)
val lift_monoid : 'a monoid -> 'a Lwd.t monoid
(** Use a monoid inside [Lwd] *)
(** {1 List reduction functions}
All reductions are balanced, relying on operator associativity.
[fold_left] would compute a chain like:
[fold f [a; b; c; d] = f a (f b (f c d)]
[reduce] uses tree-shaped computations like:
[reduce f [a; b; c; d] = f (f a b) (f c d)]
The depth of the computation grows in O(log n) where n is the length of the
input sequence.
*)
val pack : 'a monoid -> 'a Lwd.t list -> 'a Lwd.t
(** Reduce a list of elements in [Lwd] monad *)
val pack_seq : 'a monoid -> 'a Lwd.t Seq.t -> 'a Lwd.t
(** Reduce an (OCaml) [Seq.t] with a monoid *)
val reduce : 'a monoid -> 'a list -> 'a
(** Reduce a list with a monoid **)
val map_reduce : ('a -> 'b) -> 'b monoid -> 'a list -> 'b
(** Map and reduce a list with a monoid **)
(** {1 Other Lwd list functions} *)
val map_l : ('a -> 'b Lwd.t) -> 'a list -> 'b list Lwd.t
val flatten_l : 'a Lwd.t list -> 'a list Lwd.t
(** Commute [Lwd] and [list] *)