Re: Should MI be supported (was: Can MI be supported?)

["Robert I. Eachus" <rieachus@attbi.com>]

Matthew Heaney wrote:

> Bob Eachus showed how to use generic mixins to translate Hyman's example
> into Ada95, but the classes in the C++ example didn't strike me as being
> proper "mixin" classes.  Usually it's pretty obvious when a class is a
> mixin.
> 
> So can you use generic mixins to effect MI in Ada95?  Probably, yes.
> Did I think Bob's translation was very natural?  Not really, no.

I guess we just have to agree to disagree on this.  I personally find 
the mixin idiom to be more natural than the view conversion approach. 
But Ada allows both, and in fact several other ways to code the same 
example, and we are talking about adding one more.

But this is how it should be.  Ada should allow you to express a model 
using whatever patterns are most appropriate.  If we disagree on which 
patterns to use, well that is a style issue, not something where there 
is a definite right or wrong.

Of course, the other discussion in this thread is one of right and 
wrong.  If you insist on "true" isa multiple inheritance, it has to be 
inconsistant.

For those who haven't studied such fun Theory of Computation topics as 
G�del's Proof, the Halting problem, and Post's correspondence problem, 
If you have one inconsistant axiom you can prove anything. G�del's Proof 
basically says that any programming language must be either incomplete 
or inconsistant. Problems like the Halting problem and Post's 
correspondence problem cannot be solved in general in any consistant 
language. Ada is incomplete, and it will stay that way, thank you very much.

-- 
                                           Robert I. Eachus

"As far as I'm concerned, war always means failure." -- Jacques Chirac, 
President of France
"As far as France is concerned, you're right." -- Rush Limbaugh