Re: calenday (was Re: IBM Acquires Rational Ada

["Marin David Condic" <mcondic.auntie.spam@acm.org>]

Rants? Well, perhaps I have a bad habbit of typing with a "shrill" accent.
:-)

Actually, I don't really care about portability. In my business, we'd seldom
have to port something that was this machine-dependent. I'll accept a
totally vendor/processor specific answer - as is usually a requirement when
you've got to dip into rep clauses anyway.

And I wouldn't really characterize the need as relating to "weird" hardware.
I've not usually found much problem, for example, getting a rep-clause to
work to line up with some register word or other device. Usually, its a case
of someone with a communication link packing things together as tightly as
possible or from hardware substantially different from the thing doing the
reading. You get odd-sized bit fields, things that span byte or word or
longword boundaries, unusual numeric formats (1750a 48-bit float, for
example?) and things of that nature. You try to create a record that will
deal with the data and you discover your compiler is going to whine and
snivel about being asked to span things across unusual boundaries. The
instant the possibility exists that you aren't going to be able to make one
message in your catalog work with the compiler in hand, you're likely to
head for an overall solution that *will* work in all cases - id est
twiddling the bits by hand in some manner. You don't usually want to
implement 90% of the messages as records with rep-clauses and then the
remaining 10% as a byte array & access routines. You'd end up building two
totally different infrastructures and should one of your 90% ever change and
the compiler refuse to help, you're rebuilding something dramatically.

Hence (at least part of) my angst over the rep-clause. :-)

MDC
--
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Marin David Condic
I work for: http://www.belcan.com/
My project is: http://www.jast.mil/

Send Replies To: m c o n d i c @ a c m . o r g

    "I'd trade it all for just a little more"
        --  Charles Montgomery Burns, [4F10]
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Robert A Duff <bobduff@shell01.TheWorld.com> wrote in message
news:wcc3cov1hlu.fsf@shell01.TheWorld.com...
>
> On the other hand, I agree with your rants about the non-portability of
> rep clauses.  If I were designing a language from scratch, I would try
> to nail down the rules for rep clauses so that all compilers support
> exactly the same ones.  Or, at least, all compilers for the same machine
> (where "same machine" can be interpreted to mean that the various values
> in System, such as Storage_Unit and Word_Size are the same).  I think I
> would also require fairly "complete" support, in the sense of requiring
> "weird" bit fields that are extremely inefficient to access.  As you
> say, it's very frustrating to use rep clauses for 90% of the cases, and
> then be forced to use a completely different mechanism when you run
> across "weird" hardware you need to interface to.
>
> - Bob