Path: utzoo!attcan!uunet!snorkelwacker!apple!shebanow
From: shebanow@Apple.COM (Andrew Shebanow)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Multiple Inheritance -- Is It A Luxury?
Message-ID: <9007@goofy.Apple.COM>
Date: 5 Jul 90 23:09:20 GMT
References: <15132@reed.UUCP> <268BA8DC.4CD4@intercon.com> <8937@goofy.Apple.COM> <268C032E.5137@intercon.com> <1990Jul2.181147.1672@efi.com>
Organization: Apple Computer Inc., Cupertino, CA
Lines: 34

In article <1990Jul2.181147.1672@efi.com> tim@efi.com (Tim Maroney) writes:
>The people doing the MPW compilers seem to think that multiple
>inheritance is not important.  It's not possible at all in Object
>Pascal, and apparently is impossible to use in real (handle-based)
>applications in C++.  I think this is a cavalier attitude.  I've only
>been using Object Pascal for a couple of months now, and my only
>earlier OOP experience was with a flavored dialect of Franz Lisp many
>years ago; but I have already encountered a number of cases where the
>lack of multiple inheritance imposes inelegant solutions.  The
>"seaplane" analogy seems to be a frivolous way of dismissing this
>important technique.

Although it might seem hard to believe given the inflammatory tone
of Tim's missive, there are many people here at Apple who think
that MI is important. I suggest that you all read the article by
David Goldsmith and Jack Palevich in the latest issue of
d e v e l o p for some useful MI guidelines that we use internally.

The limitations on the use of MI in handle based objects are caused
by C++'s object model, and not by a lack of concern on the part
of Apple's engineers. If anyone can figure out a good way to solve
this problem without rewriting all of CFront, we would of course be
very interested in hearing about it.

Object Pascal doesn't support MI primarily for historical reasons.
The language wasn't designed with MI in mind, and adding MI
to it would be a decidedly non-trivial change. However, Apple's
Advanced Technology Group is looking at doing an updated
version of the Object Pascal language - for more information,
see the last issue of the MacApp Developer's Association publication,
Frameworks".

Andy Shebanow
Apple Computer, Inc.