Re: Dimensionality Checking (Ada 20XX)

["Nick Roberts" <nickroberts@adaos.worldonline.co.uk>]

"Mark Johnson" <Mark_H_Johnson@Raytheon.com> wrote in message
news:3C168DB0.C139DC2@Raytheon.com...

> > But nothing prevents a compiler from implementing fixed point
> > operations/representations using the hardware's floating point
unit/format.
> > (Am I wrong?)

> Its been a while since I've done fixed point arithmetic, but I believe
> you are wrong.
> ...
> You can't represent a Bam in a 32 bit floating point - not enough
> precision. Of course, our orbital models are now done in 64 bit floating
> point, so the original comment is certainly accurate on a lot of systems
> these days.

That's actually exactly what I meant.

> I would tend to use fixed point for the following cases...
>  - interfaces to hardware
>  - small target systems
>  - where I need absolute control of error
> and floating point everywhere else.

With respect, Mark (and in deference to the practicalities of actual Ada
implementations), perhaps you shouldn't.

Or at least, perhaps in many of those cases where you use floating point
(because fixed point offers no great advantage), you would use a fixed point
(unit-specific) type so as to gain the advantage of dimension checking (or
unit conversion). Would it actually be problem to do this?

--
Best wishes,
Nick Roberts