class type num = 
object
  method get_val : float
  method add : num -> unit
  method parse : string -> unit
end

class int = 
object
  val mutable x = 1
  method get_val = float x
  method add : num -> unit = fun o -> x <- (int_of_float o#get_val) + x
  method parse s = x <- int_of_string s
end

class float = 
object
  val mutable x = 1.
  method get_val = x
  method add : num -> unit = fun o -> x <- o#get_val +. x
  method parse s = x <- float_of_string s
end

let make_obj = function
  | "float" -> (new float :> num)
  | "int" -> (new int :> num)
  | _ -> invalid_arg "which module"

let parse s = make_obj s
    
let do_repetitive_work x =
  let y = Oo.copy x in
  y#add x;
  y#add (Oo.copy x);
  y

let () = 
  let x = parse Sys.argv.(1) in
  Printf.printf "%g\n" (do_repetitive_work x)#get_val