Re: GNAT versions ( was :Ada compiler for PC?)

[Robert Dewar <robert_dewar@my-dejanews.com>]

In article <FB8DLq.BH6@kithrup.com>,
  mrs@kithrup.com (Mike Stump) wrote:
> In article <7gbjhg$s98$1@rtl.cygnus.com>,

> I don't think any of this was related to GNAT.  My take is just a
> simple conflict of styles.  It only delayed EH by 2-7 years.  My
> choice, would have been to not delay it, and just get it working, then
> working well, then well ported, then clean up the interfaces and
> documentation.


That certainly seems backwards to me, for me the sequence of
software production goes like:

design and document the interfaces
refine the interfaces till they are correct
then implement

I find the style of doing things backwards worrisome, though I
realize it is common enough, especially in the C community.

We certainly follow this procedure internally at ACT. If someone
thinks a new feature is useful, then first we have a general
discussion of the idea, then we design the feature (e.g. package
specs are produced and reviewed), then we do the implementation
of the bodies. I doubt this description of normal software
design procedures seems strange, at least I would expect it
was entirely familiar to the comp.lang.ada users reading this!

The trouble with doing things backwards is that you are realying
FAR too heavily on testing alone as the criterion for correctness.
Even if there were a comprehensive and systematic test suite,
including significant amounts of code, testing is never sufficient
on its own to ensure that your design is correct.

I must say I am a little puzzled by Mike's reluctance to document
things. If EH was really delayed 7 years because of this (I think
that's a bit of an exaggeration :-) it is a pity ...

As to whether one should bend the rules and allow things to be
implemented without documentation, and instead hope for documentation
to appear later, it's hard to say. Sometimes you DO have to make
this compromise, but it often does not work out well. The trouble
is that many people who have this code-now, document-later approach
have a lot of trouble coming through with the documentation later.

For me personally, writing well documented code is a pleasure, sort
of like writing a text book that students like to read. If code is
accessible and easy to understand, and good documentation is part
of the reason, then that is a pleasing achievment in itself. I get
the impression that a lot of programmers don't share this view, and
find documentation a nuisance -- too bad.

P.S. I still find the documentation of the exception handling stuff
in GCC inadequate. This may be just lack of skill on my part in
reading C code of this kind (clearly there is an expectation that
you figure out some of the details of the specification by looking
at the details of the coding, which I find uncomfortable.

One unfortunate consequence is that the GNAT exception handling has
been developed entirely independently, and I suspect that there
could be more merging, though I am not sure of this, because to have
an exception handling mechanism usable by both C++ and Ada 95, a
perfectly reasonable goal, would require careful examination of
the specifications *before* starting to implement.

Anyway, I do agree with Mike on one important point, the exception
handling requirements for GNAT had nothing at all to do with the
development of EH handling in GCC!

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