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module type PT = sig
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
end
module Single = struct
type 'a t = S of 'a
let unpack : 'a t -> 'a = fun (S x) -> x
let pack : 'a -> 'a t = fun x -> S x
let map ~f a = pack (f (unpack a))
let map2 ~f a b = pack (f (unpack a) (unpack b))
let iter ~f a = f (unpack a)
let iter2 ~f a b = f (unpack a) (unpack b)
end
module Pair = struct
type 'a t = P of 'a * 'a
let unpack : 'a t -> 'a * 'a = fun (P (x, y)) -> x, y
let pack : 'a * 'a -> 'a t = fun (x, y) -> P (x, y)
let map ~f a =
let x, y = unpack a in
pack (f x, f y)
let map2 ~f a b =
let xa, ya = unpack a in
let xb, yb = unpack b in
pack (f xa xb, f ya yb)
let iter ~f a =
let x, y = unpack a in
f x;
f y
let iter2 ~f a b =
let xa, ya = unpack a in
let xb, yb = unpack b in
f xa xb;
f ya yb
end