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From: franka@mentor.com (Frank A. Adrian)
Newsgroups: comp.object
Subject: Re: Inheritance explained... finaly...
Keywords: inheritance
Message-ID: <1990Jan11.154007.3947@mentor.com>
Date: 11 Jan 90 15:40:07 GMT
References: <1130005@gore.com> <14185@lambda.UUCP> <1831@osc.COM>
Reply-To: franka@mntgfx.UUCP (Frank A. Adrian)
Organization: /etc/organization
Lines: 39

In article <1831@osc.COM> jgk@osc.COM (Joe Keane) writes:
:In article <14185@lambda.UUCP> jlg@lambda.UUCP (Jim Giles) writes:
:>In any case, I still have doubts about the future of Object-oriented
:>programming.  After all, except for inheritance, the whole concept
:>is a subset of what can be done with generic functions and overloading.
:>Maybe the correct approach is to add inheritance to a language which
:>has generic functions - it can't be THAT hard.
:
:Mr. Giles has a number of good points.  Let me quickly enumerate the bad
:points of the object-oriented paradigm as it stands today.
:
:Type system...
:Multiple inheritance fixes a number
:of these problems, but usually complicated things even further.  I have yet to
:see a language which does multiple inheritance cleanly.
:
:Multiple arguments.  Forcing the first (implicit) argument to be special is
:bogus...
:Polymorphism should not be indexed on the class of the first argument.
:
:Side effects.  Object orientation includes a vague assumption that messages
:modify their receivers, but not their parameters.

So what's the problem?  You have a language that does somewhat better on ALL
of these - CLOS.  Not only does it have multimethods and generic functions
(See Mr. Giles' suggestion and the stuff about multiple arguments), it
also has a fairly controllable multiple inheritance system (although I agree,
it sometimes isn't exactly clean - is that simply a problem with describing
real world multiple roles which objects can play?).  Side effects can be
performed on message parameters (or not).

All in all, it seems like a pretty good language (especially if you like LISP
in the first place :-).

Just my own somewhat grumpy opinion...

Frank A. Adrian
Mentor Graphics, Inc.
franka@mntgfx.com