objects.ml

class virtual abox rc = object(self)
val mutable children = []
end;;
class virtual abox : 'a -> object val mutable children : 'b list end                                                                                          

class vbox = object(self)
inherit abox "vbox" end;;
class vbox : object val mutable children : 'a list end                                                                                                        
class polling_box =
object
inherit vbox
method replace_children () =
children <- [] end;;
class polling_box : object val mutable children : 'a list method replace_children : unit -> unit end