type pt = {
  get_x : unit -> int; 
  set_x : int -> unit;
  distance : pt -> int;
}
let point1_constructor () = (* unit -> pt *)
  let x = ref 0 in
  let rec self =
    { get_x = (fun () -> !x);
      set_x = (fun y -> x := y);
      distance = (fun p -> p.get_x() - self.get_x() )
    } 
  in self

(* this won't type-check, but even if it did, it would not
   do dynamic dispatch, the essence of OOP *)
(*
let point2_constructor () =
  let r = point1_constructor () in
  let y = ref 0 in
  let rec self =
    { get_x = (fun () -> 34 + r.get_x());
      set_x = r.set_x;
      distance = r.distance;
      get_y = (fun () -> !y) } 
  in self
*)