binary_module.ml

module Shapes : sig
  type shape_repr
  type shape =
    < repr : shape_repr; equals : shape -> bool; area: float >

  class square : int ->
    object
      method width : int
      method area : float
      method repr : shape_repr
      method equals : shape -> bool
    end
end = struct
  type shape_repr = 
  | Square of int 
  | Circle of int 
  ...
end