Re: OS Bindings (was: Where is the elusive jump command?)

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

In article <wccbt3fayqe.fsf@world.std.com>,
  Robert A Duff <bobduff@world.std.com> wrote:

> I agree about subscripts and entry families, but I don't see
> the problem
> with case statements.

Because it is not significantly useful to have case statements
operating with 256-bit integer values, and it is likely that
standard optimizers etc do not deal with this special case,
meaning that it has to be special cased by the compiler,
creating special cases that require lots of extra testing
work etc.

>  Loops?  I dunno.

Same thing.

It is really surprising to many people that Ada compilers often
do not support 64-bit arithmetic. In GNAT, we do guarantee
64-bit integer arithmetic on all targets (Long_Long_Integer
is at least 64-bits), but it does take extra work, and I
suspect that a significant part of the reason that it is not
done on all targets is that it is too much work to deal with
loops, case statements, subscripts etc, and if you are allowed
to simply avoid these issues by refusing to support it at all
then that's the easier choice.

> I think that is clear.  I'm too lazy to look up the RM
reference.  I do
> remember that William Whitaker griped about this allowance
rather
> strongly, which surprised me, because it seemed to me silly to
say (to a
> compiler writer) you don't have to support X, but if you do
support X,
> you have to *fully* support it.

Indeed, and that is my point, I think we are in basic
agreement here.



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