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Date: 29 Apr 93 16:02:59 GMT
From: netnews!schonberg!dewar@nyu.edu  (Robert Dewar)
Subject: Re: A measure of Ada's death in the database world
Message-ID: <dewar.736099379@schonberg>
List-Id: <comp.lang.ada>

	class type x is new a,b,c;

Well first of all, that syntax isn't quite right, since it doesn't allow
for extensions, and also we don't use class in 9X in this way, so what I
would expect would be something like:

	type x is new a,b,c with ...;


It's easy enough to write syntax like this, but there are big semantic problems
and big implementation problems (just to mention a couple, what about virtual
base classes, and how do you avoid distributed overehead from the *possibility*
of MI even if it isn't used -- C++ compilers usually pay such a distributed
overhead).

It's these semantic and implementation problems that make one think twice (or 
perhaps ten times) before including MI in 9X. I certainly haven't seen anyone
complete a thorough design for such a feature which addresses all these
problems.

The real question is whether it is worth it. The post that this responds to
talks about using kludges, but one guys kludge is another guys elegant
approach. For instance, to an Ada programmer, having to use classes in C++
for what are better represented as packages, and then having to use multiple
inheritance for what is better represented by multiple package dependencies
is indeed a kludge -- but the kludge is in C++, not in Ada.

Despite a lot of attempts and requests, the discussion of MI in 9X has
generated a lot of suggestions that it should be included, but precious
few examples of programming examples that make this case in even a
semi-convincing form.