include PT
type 'a t
val map : f:('a -> 'b) -> 'a t -> 'b tval map2 : f:('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c tval iter : f:('a -> unit) -> 'a t -> unitval iter2 : f:('a -> 'b -> unit) -> 'a t -> 'b t -> unit
val unpack : 'a t -> 'a * 'aval pack : ('a * 'a) -> 'a t