Re: Clean Object Class Design -- Circle/Ellipse

"Marc Gluch" <marc.gluch_at_mindtap.com> wrote in message news:3b81d266.3858753634_at_news.grpvine1.tx.home.com...
> On Mon, 20 Aug 2001 03:19:30 GMT, "Richard MacDonald"
> <macdonaldrj_at_att.net> wrote:
>
>
> >> I think I mentioned it in some earlier post.
> >> Magnitude provides axiomatization of the ordering relationship ("<").
> >> Number (derived from Magnitude) overrides "< " appropriately for its
> >> domain.
> >>
> >Got it. You moved that up a little higher again. (I am a Smalltalker.)
> >I'm still lost on the issue of the operations that "jump outside" the
> >argument's domain. Are you saying that any operation that does so
> >must move up the hierarchy until it encompasses both the argument
> >and the result? So you disallow the "jump"?
>
> I'm not sure about the meaning you assign to "jump".

Lousy word on my part. Having the result of an operation be a type unrelated to the argument type. The age of a Person is an Integer. Person and Integer are not related types.

> The way I prefer to put it is to say that
> one specialization/implementation should not redefine another.
> They all should be (parallel) implementations of a generic
> (ala CLOS) function.
>

Ok, but this confuses me. You seemed to be trying to build up the type theory strictly from axioms that were limited to staying "within" a type hierarchy. The above statement does not have this limitation.

P.S. If I'm confused, I bet I'm not the only one. I am stealing Bob's example, after all :-) Received on Mon Aug 20 2001 - 23:34:13 CDT