David Chemouil writes:
> > # class a (arg : a -> b) = object(self)
> >     val ob = arg self
> >   end
> >   and b = object
> >   end;;
> > The instance variable self
> > cannot be accessed from the definition of another instance variable
> > I don't understand why it is forbidden for an object to pass itself to
> > another one
> >  (which is possible in Java or Eiffel for example). 

You can write your example just like in Java, by 1- making the
instance variable mutable, and 2- using an option type to play the
role of Java's null pointers.  You'd get:

class a arg = object(self)
    val mutable ob = (None : b option)
    initializer ob <- Some(arg self)
  end;;

It's not pretty, but that's exactly what's going on "under the hood"
in the equivalent Java code.

- Xavier Leroy