Xref: utzoo comp.lang.c++:3349 comp.lang.eiffel:194 comp.lang.smalltalk:1082
Path: utzoo!attcan!uunet!tektronix!sequent!mntgfx!plogan
From: plogan@mntgfx.mentor.com (Patrick Logan)
Newsgroups: comp.lang.c++,comp.lang.eiffel,comp.lang.smalltalk
Subject: Re: Use of inheritance for classification?
Message-ID: <1989May16.112934.14250@mntgfx.mentor.com>
Date: 16 May 89 18:29:32 GMT
References: <30582@apple.Apple.COM>
Organization: Mentor Graphics Corporation, Beaverton Oregon
Lines: 38
In-reply-to: kmcentee@Apple.COM's message of 12 May 89 23:16:07 GMT


In article <30582@apple.Apple.COM> kmcentee@Apple.COM (Kevin McEntee) asks:
=?   Can code sharing outside of the natural taxonomy of the problem
=? space happen gracefully?

Here are some thoughts, written humbly as a would-be OO programmer not
as an expert sage. (Just in case it comes across that way.)

Perhaps in "Object Oriented Programming" there is no difference
between code sharing and classes sharing a common class. In languages
that are nearly "pure" OOLs (e.g. Smalltalk, Eiffel) it seems there is
no way to share code without specifying the sharing as a common super
class.

Is there a reason to share code some other way? In hybrid OOLs such as
CLOS and C++ it's possible to revert to creating good old procedures.
What would be a reasonable situation to do so? I usually think of
doing so in order to create a local procedure as a part of
implementing a particular method. Or to be shared between methods of a
particular class. If I was sharing a procedure in methods of disparate
classes I would probably look for a missing link in the class
taxonomy.

Also, there's an article* that suggests an "algorithm" should in some
cases be considered an object, e.g. FFTs. So one could create a class
for a particular procedure or group of procedures that may not usually
be considered objects. These would probably be few and far between.



* "Using Types and Inheritance in Object Oriented Programming",
  Halbert, Daniel C. and Patrick O'Brien, (both at DEC)
  IEEE Software, Sept. 1987

-- 
Patrick Logan                | ...!{decwrl,sequent,tessi}!mntgfx!plogan 
Mentor Graphics Corporation  | plogan@pdx.MENTOR.COM                    
Beaverton, Oregon            | "My other computer is a Lisp machine."