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Date: Fri, 10 Mar 2000 09:33:24 +0100
From: Xavier Leroy <Xavier.Leroy@inria.fr>
To: Didier Remy <remy@pacherenc.inria.fr>,
        David Chemouil <David.Chemouil@enseeiht.fr>
Cc: caml-list@inria.fr
Subject: Re: typing of a class
References: <38C50056.9A272C81@enseeiht.fr> <m38bt4n3n7u.fsf@pacherenc.inria.fr>
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In-Reply-To: <m38bt4n3n7u.fsf@pacherenc.inria.fr>; from Didier Remy on Thu, Mar 09, 2000 at 09:25:25PM +0100
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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