Traversable_types.Generic_on_monad
Generic_on_monad
extends Generic_on_applicative
to contain various derived operators that require monads; we use it to derive the signatures of the various On_monad
modules.
'a t
becomes t
and 'a elt
becomes elt
.'a t
becomes 'a t
and 'a elt
becomes 'a
.All applicative operators are available through lowering the monad to an applicative functor.
include Generic_on_applicative with module M := Monad_exts.App(M)
include Basic_generic_on_applicative with module M := Monad_exts.App(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 Generic_types.Generic
val map_m :
('a, 'phantom) t ->
f:('a elt -> 'b elt Travesty.Monad_exts.App(M).t) ->
('b, 'phantom) t Travesty.Monad_exts.App(M).t
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
val fold_map_m :
('a, 'phantom) t ->
f:('acc -> 'a elt -> ('acc * 'b elt) M.t) ->
init:'acc ->
('acc * ('b, 'phantom) t) M.t
fold_map_m c ~f ~init
folds f
applicatively over every t
in c
, threading through an accumulator with initial value init
.
fold_m x ~init ~f
folds the applicative computation f
over x
, starting with initial value init
, and returning the final value inside the applicative effect.
iter_m x ~f
iterates the computation f
over x
, returning the final applicative effect.