Re: Multiple Inheritance in Ada 9X

[odi!dlw@uunet.uu.net (Dan Weinreb)]

In article <22010@alice.att.com> bs@alice.att.com (Bjarne Stroustrup) writes:

   As with other features that are new to the majority of programmers there
   has been quite a debate about multiple inheritance. My impression is that
   most of the debate has been among language laywers and that much have been
   misguided in that it has focussed on obscure points of language law and
   at best weakly supported by experience or notions of programming style.

Yes, I think you've stated it very well.

There have indeed been debates, at OOPSLA and in other forums, about
various designs for multiple inheritance features.  I think most
reasonable people agree that none of the present designs seems to be
perfect.  None is the absolute undisputed last word about the Right
Way to do MI.  In most of them, it is possible to construct complex
scenarios in which the behavior of the language, although
well-defined, can become difficult to understand and possibly
surprising.

But to say that this means that MI should be shunned or banned is to
let the perfect become the enemy of the good.  After all, I think
there are flaws in many areas of many languages, but that doesn't mean
we should all go back to assembly language.  Present MI features are
very useful for many everyday practical purposes despite their flaws,
and this has been shown by many years of experience.  The problems are
of much more interest to language designers and theoreticians (who are
strongly represented at OOPSLA) than to practical programmers.  The
language designers and theoreticians should, by all means, spend time
analyzing the flaws in all the existing languages, and attempting to
come up with improved approaches.  Meanwhile, though, the practical
programmers need not shun existing MI languages.  Instead, they should
understand how to use them as well as they can be used, and I think
they'll find that the effort is worthwhile.