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

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

In article <8d457u$5n33@ftp.kvaerner.com>,
  "Tarjei T. Jensen" <tarjei.jensen@kvaerner.com> wrote:

> I think it is a glaring oversight in the standard if it not
> only allows, but
> requires compilers to honour a definition like the one above.
> I don't have the
> final version of the RM here, only the June 94 version.


Great, so here we go again. Obviously we can't mandate 64-bit
integer support, since the burden would be too great on small
processors. And if you disagree, just change 64 to a larger
power of 2.

Tarjei says

"if you implement n-bit arithmetic, then you must implement
full range unsigned n-bit arithmetic with overflow checking."

AARGH! the Ada 83 mentality at work again. The mentality that
says, you don't need to implement X, but if you implement X
you must implement Y.

I trust that Tarjei understands that it would be a lot of
extra work to implement this new form of checked arithmetic.
The consequence of Tarjei's suggested change might well be
that compilers decide, "oh well, 64-bit integer arithmetic
is too much of a pain anyway", and simply don't do it at all.

Suppose this "glaring defect" were fixed in the RM.

Then GNAT would have a lot of extra work to do, maybe we would
do it, but maybe we would simply remove 64-bit arithmetic
completely (actually put it under an extension switch) so it
was not considered part of the core.

Never encourage implementors to do less by making it harder
than necessary for them to do more!

We have unsigned 64-bit arithmetic similar to the capabilities
of C (well at least GNU-C) and Java in Ada. Yes, that's not
ideal, and for many applications a range checked 64-bit range
would be better. But please don't let best be the enemy of good.


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