Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!uunet!odi!dlw
From: dlw@odi.com (Dan Weinreb)
Newsgroups: comp.object
Subject: Re: Examples of Multiple Inheritance?
Message-ID: <1990Dec7.202753.22656@odi.com>
Date: 7 Dec 90 20:27:53 GMT
References: <60700005@inmet> <1990Dec6.020928.13319@Think.COM>
Reply-To: dlw@odi.com
Organization: Object Design, Inc.
Lines: 21
In-Reply-To: barmar@think.com's message of 6 Dec 90 02:09:28 GMT

In article <1990Dec6.020928.13319@Think.COM> barmar@think.com (Barry Margolin) writes:

				    and C++ doesn't make it nearly as easy to
   make use of MI (perhaps Dan Weinreb, who has migrated from Flavors to C++,
   could comment on this).

That's right.  In a nutshell, the basic difference is that in CLOS, a
"mixin" flavor can be an independent, reusable module.  You can build
new flavors by inheriting from pre-existing mixins, and they all join
together and work, without modification of code.  C++ does not have
this concept, and modification of code is needed much more frequently,
because individual classes in C++ have the names of parent classes
textually embedded within them.  The fundamental facility of CLOS that
C++ lacks is "call-next-method".

(I bet that another reason that there is presently less experience
than you might expect with C++ MI is that the AT&T-based
implementations still have some implementation problems, particularly
with virtual base classes.  This has nothing to do with C++, the
language definition, of course, but it affects its manner of usage in
the short term.)