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Re: Clean Object Class Design -- Circle/Ellipse

From: Jan Hidders <hidders_at_REMOVE.THIS.win.tue.nl>
Date: 1 Sep 2001 18:04:52 GMT
Message-ID: <9mr804$a3a$1@news.tue.nl>


Bob Badour wrote:
>
> Jan Hidders wrote in message <9md6po$fp4$1_at_news.tue.nl>...
> >Bob Badour wrote:
> >>
> >> Fair enough. If one overrides a property such that it alters the
> >> semantics of the inherited property, one no longer has a subtype.
> >> However, I would consider such an override as nothing more than an
> >> abuse of the subtyping mechanism.
> >
> >Er, you mean the 'inheritance mechinism'? :-) But I agree with you that
> >such overriding would be bad design.
>
> No, I mean subtyping mechanism. If I use my screwdriver to stir a
> cocktail, I misuse my screw driving mechanism and not my drink
> stirring mechanism. <g>

Overriding is not a meaningful concept in the context of subtyping. There is a difference between subtyping and inheritance, you know. The first is about specification and the latter is about implementation. Somehow I get the feeling you think these concepts are the same. Please don't mix the two. You'll get a headache or at least waste a lot of time with discussions that are caused by misunderstandings. I've seen a lot of discussions between database researchers and programming language researchers go wrong that way.

-- 
  Jan Hidders
Received on Sat Sep 01 2001 - 13:04:52 CDT

Original text of this message

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