open Batteries

class type ['a] number = object ('b)
  method value: 'a
  method plus: 'b -> 'b
end

class int_wrap (i: int) = object
  val i = i
  method value = i
  method plus (other: int number) = {< i = i + other#value >}
end

class float_wrap (f: float) = object
  val f = f
  method value = f
  method plus (other: float number) = {< f = f +. other#value >}
end

let parse: string -> 'a number = fun s ->
  if String.exists s "." then
    float_of_string s |> new float_wrap
  else
    int_of_string s |> new int_wrap