Module type WithM.MonadError

module type MonadError = sig .. end

type +'a m 

val return : 'a -> 'a m

val bind : ('a -> 'b m) ->
       'a m -> 'b m

val bind_rev : 'a m ->
       ('a -> 'b m) -> 'b m

val error : exn -> 'a m

val catch : (unit -> 'a m) ->
       (exn -> 'a m) -> 'a m