Of_monad2.1-M
type ('a, 'e) t
val return : 'a -> ('a, _) t
val map : ('a, 'e) t -> f:('a -> 'b) -> ('b, 'e) t
val apply : [ `Custom of ('a -> 'b, 'e) t -> ('a, 'e) t -> ('b, 'e) t | `Define_using_bind ]
val bind : ('a, 'e) t -> f:('a -> ('b, 'e) t) -> ('b, 'e) t