Re: Clean Object Class Design -- Circle/Ellipse

Jan Hidders wrote in message <9mr804$a3a$1_at_news.tue.nl>...
>Bob Badour wrote:
>>
>> Jan Hidders wrote in message <9md6po$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.

Of course.

>The
>first is about specification and the latter is about implementation.

I agree -- that's why I called inheritance the mechanism for subtyping.

>Somehow I get the feeling you think these concepts are the same.

No more than I think fastening with screws is the same as a screwdriver. Received on Sun Sep 02 2001 - 05:05:27 CEST