Make.2-P
type 'a t
val map : f:('a -> 'b) -> 'a t -> 'b t
val map2 : f:('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t
val iter : f:('a -> unit) -> 'a t -> unit
val iter2 : f:('a -> 'b -> unit) -> 'a t -> 'b t -> unit