Re: Q: access to subprogram

[dewar@cs.nyu.edu (Robert Dewar)]

Jon says

"While the lack of direct support for recursive types across package
boundaries and lack of assertions are more important (IMO) goofs, and
while the evinced reasons for the latter one are mind numbingly
incomprehensible, this latest example would appear to take the crown
for the most stupefying goof."

Well it is always easy for users to decide that they want everything
and don't want to worry about the required resources, but a language
design can't be quite that cavalier in balancing requirements.

The fact of the matter is that providing for displays to work reasonably
easy *has* had value in getting at least some Ada 95 compilers to market
more easily than might have otherwise been the case.

I think everyone agrees that it is valuable to have several compilers
competing, and the balance in features vs implementability was always
a tricky one. Note that we did lose one compiler (the DEC Ada compiler),
and a large part of the reason for DEC's decision to get out of the
Ada compiler business was that they estimated it was too expensive
to modify their technology for Ada 95.

We have also lost at least one front end (the old Alsys technology, and
before that the Systeam technology), and more may dissappear before we
are through. At least the Alsys code generators proved largely adaptable
to Ada 95. Of course we have gained at least two new front ends (GNAT and
Intermetrics, so the front end situation looks healthy, although it is
interesting that both of these front ends were "from scratch".

One of the key requirements in the design was that Ada 95 not be such
a big change that it would be impractical to adapt existing Ada 83
front ends. At some points in the design, some people expressed the
opinion that this was impractical, and that we should assume that
"from scratch" development was the only practical path, but WG9
insisted on a  viewpoint that we should not restrict things in this
way. It appears that we at least partially succeeded, since at least
two Ada 95 front ends *are* adaptations of Ada 83 frontends.

There is certainly no doubt that Ada 95 is close to the limits of
acceptable front end complexity. Of course when you look at individual
features, it is hard to label any one feature as a back-breaking straw,
but that's what that little fable is all about after all :-)