Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ames!think!barmar
From: barmar@think.COM (Barry Margolin)
Newsgroups: comp.lang.lisp
Subject: Re: Comparison of CLOS and New Flavors
Keywords: CLOS, New Flavors
Message-ID: <28870@news.Think.COM>
Date: 5 Sep 89 23:34:30 GMT
References: <4640@lindy.Stanford.EDU> <34538@apple.Apple.COM>
Sender: news@Think.COM
Organization: Thinking Machines Corporation, Cambridge MA, USA
Lines: 36

In article <34538@apple.Apple.COM> malcolm@Apple.COM (Malcolm Slaney) writes:
>As near as I can tell.....CLOS is the superset of all existing lisp 
>object oriented extensions :-).

Not quite.  There are a numberof features in Flavors that don't exist
in CLOS.  Symbolics sent a document, "Getting Ready for CLOS", to
their customers a couple of months ago (they also gave out copies at
the SLUG conference in June).

The most noticeable difference between Flavors (old and new) and CLOS
is the lack of SELF.  CLOS permits methods to be specialized on the
data type of more than one argument, so there is no distinguished
argument that should be SELF.  A corollary to this is that it SELF's
instance variables (called "slots" in CLOS) are not automatically made
accessible as if they were local variables; the macros WITH-SLOTS and
WITH-ACCESSORS can be used to make a particular variable's slots
accessible as variables.

Various New Flavors facilities that exist only for compatibility with
Old Flavors do not exist in CLOS.  For instance, the SEND function
doesn't exist.

CLOS doesn't have any of the DEFxxx-IN-FLAVOR macros.  They don't
really make much sense when methods aren't associated with particular
classes.  CLOS also doesn't have wrappers.

Many DEFFLAVOR options don't have analogous DEFCLASS options.  Some of
these are esoteric (e.g. :SPECIAL-INSTANCE-VARIABLES, which I think
was created just to make it easier to flavorize Zwei), but others may
have been used by many users (e.g. all the :REQUIRED-xxx options).

Barry Margolin
Thinking Machines Corp.

barmar@think.com
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