Singleton.On
On
implements applicative folding and mapping operators for a given applicative M
, including arity-1 specific operators.
include Travesty.Traversable_types.Generic_on_applicative
with type ('a, 'phantom) t := 'a t
and type 'a elt := 'a
with module M := M
include Travesty.Traversable_types.Basic_generic_on_applicative
with type ('a, 'phantom) t := 'a t
with type 'a elt := 'a
with module M := M
Generic
refers to the container type as 'a t
, and the element type as 'a elt
; substitute t
/elt
(arity-0) or 'a t
/'a
(arity-1) accordingly below.
include Travesty.Generic_types.Generic
with type ('a, 'phantom) t := 'a t
with type 'a elt := 'a
map_m c ~f
maps f
over every t
in c
, threading through an applicative functor.
Example:
(* Travesty_base_exts.List adds applicative traversals to a list;
With_errors (in S1_container) implements them on the On_error
applicative functor. *)
let f x =
Or_error.(if 0 < x then error_string "negative!" else ok x)
in
List.With_errors.map_m integers ~f