From mboxrd@z Thu Jan  1 00:00:00 1970
Received: (from weis@localhost) by pauillac.inria.fr (8.7.6/8.7.3) id JAA16508 for caml-redistribution; Tue, 14 Sep 1999 09:22:20 +0200 (MET DST)
Received: from nez-perce.inria.fr (nez-perce.inria.fr [192.93.2.78]) by pauillac.inria.fr (8.7.6/8.7.3) with ESMTP id QAA03672 for <caml-list@pauillac.inria.fr>; Mon, 13 Sep 1999 16:07:29 +0200 (MET DST)
Received: from isil.maya.com (isil.maya.com [192.70.254.5])
	by nez-perce.inria.fr (8.8.7/8.8.7) with ESMTP id QAA18336;
	Mon, 13 Sep 1999 16:07:15 +0200 (MET DST)
Received: (from prevost@localhost)
	by isil.maya.com (8.9.3/8.9.3) id KAA23083;
	Mon, 13 Sep 1999 10:10:09 -0400
Sender: weis
To: Didier.Remy@inria.fr
Cc: caml-list@inria.fr, Kim Bruce <kim@bull.cs.williams.edu>
Subject: Re: Ocaml 2 object system origins
References: <m33dws495j.fsf@isil.maya.com> <19990913151557.26714@morgon.inria.fr>
From: John Prevost <prevost@maya.com>
Date: 13 Sep 1999 10:10:08 -0400
In-Reply-To: Didier.Remy@inria.fr's message of "Mon, 13 Sep 1999 15:15:57 +0200"
Message-ID: <m3so4inbr3.fsf@isil.maya.com>
User-Agent: Gnus/5.070096 (Pterodactyl Gnus v0.96) Emacs/20.4
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii

Ahh.  Thanks very much--I recalled that there were some papers about
this, but poked around the web page a bit ineffectually.

On the topic of folklore and matching, you say:

> On the other hand, the language LOOM uses a new notion called
> matching (<#) and primitive self-types. It is folklore (but I don't
> think it has ever been checked formally) that matching does not
> accomplish more than polymorphism over row-variables.

Hmm.  My intuition on looking at the two systems is to believe that,
if anything, polymorphism over row-variables *might* be more powerful.

Unfortunately, the comparison is complicated, since LOOM allows
variables of type #foo, and in O'Caml #foo is a synonym for a
type-expression with an unbound type variable (implying that this type
must be unified to a single type except in polymorphic function
types.)  (It's so worrying when intuition can be confused in this
way.)

In any case, I'll have to do more reading and comparison now that I
have descriptions of both systems available to me.

Thanks very much for the excellent explanation.

John