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

class int = 
object
  val mutable x = 0
  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 = 0.
  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 parse s =
  let ret = if String.contains s '.' then (new float :> num) else (new int :> num) in
  ret#parse s;
  ret