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Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!dali.cs.montana.edu!uakari.primate.wisc.edu!samsung!uunet!bony1!richieb
From: richieb@bony1.bony.com (Richard Bielak)
Newsgroups: comp.object,comp.lang.eiffel
Subject: Unification: Class=Type=Module
Message-ID: <1991Apr23.142800.12215@bony1.bony.com>
Date: 23 Apr 91 14:28:00 GMT
Reply-To: richieb@bony1.UUCP (Richard Bielak)
Organization: Bank of New York
Lines: 25


One of the things I liked about "Object Oriented Software Construction"
by B. Meyer, was the idea that a class is both a type and a module.
This idea clears up the confusion as to whether inheritance extends or
specializes.

When a class is considered to be a type, inheritance specializes the
type. The descendent type is type-compatible with fewer things, so it
is more specialized.

When a class is considered to be a module, inheritance adds more
routines and attributes. Since the class can do more things it has
been  extended.

I also like the "cleanness" and simplicity of this idea. 

I am curious whether other people think about this, and whether such
"unification" has any disadvantages.

...richie
-- 
*-----------------------------------------------------------------------------*
| Richie Bielak  (212)-815-3072    | Programs are like baby squirrels. Once   |
| Internet:      richieb@bony.com  | you pick one up and handle it, you can't |
| Bang:       uunet!bony1!richieb  | put it back. The mother won't feed it.   |