Re: Fixed point design error in Ada95

[dewarr@my-dejanews.com]

In article <6t9dlk$e0t1@onews.collins.rockwell.com>,

> I'll certainly agree with you that there aren't a lot of uses for
> fixed-point operator overloading.
>
> We are running host-based simulations of avionics systems which run
> on a special avionics processor.  That processor does not have
> floating point, but has something called fractional arithmetic.
>
> The fractional arithmetic does not work exactly the same way as
> Ada's fixed point.  There is no overflow detection with this
> hardware, which is why the operator must be overloaded in order
> to properly simulate the way the software will operate in the
> target.  The target compiler is an Ada83 compiler, but the host
> compiler is an Ada95 compiler.
>
> It is unfortunate that Ada95 is not 100% backward compatible in
> this area, even if it has little impact on the user community.
>
> A pragma to give Ada83 operation would be a good solution.
>
> Thanks,
> Wayne.


First, a note, Ada does not require overflow detection for
fixed-point, you seem from the above to think it does, so
that is not a problem with your processor. The provision of
the Machine_Overflows attribute is intended precisely to
take care of this situation.

Second, you obviously don't need operator overloading, there
are perfectly reasonable work arounds here. They are a bit
annoying, but certainly acceptable for new code.

I agree that with legacy code you are in trouble, this is
indeed one of the most severe incompatibilities between
Ada 83 and Ada 95. I shouted around insisting that we should
fix it when it was first noticed (which was rather late), but
it seemed "too-late-at-this-stage" to do anything about it
to most people, and perhaps they were right.

-----== Posted via Deja News, The Leader in Internet Discussion ==-----
http://www.dejanews.com/rg_mkgrp.xp   Create Your Own Free Member Forum