(* An Interface Intervenes *)

let ap : (int -> int) -> int -> int =
  fun (f: int -> int) ->
    fun (x: int) ->
      f x

let iap = (ap :> (int -o int) -> int -o int)

let inc : int -> int =
  fun (y: int) ->
    (fun (g: int -o int) ->
       iap g y)
    (fun (z: int) -> z + 1)

in print (inc 5)