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 (inc 5)