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

let inc : int -> int =
  fun y: int ->
    let g = (fun z:int  -> z + 1 : int -> int :> int -o int) in
      ap g y         (* g: (int -o int) is used as an (int -> int) *)

in print[int] (inc 5)