Re: conversions between fixed-point types

["Jeffrey R. Carter" <spam.jrcarter.not@spam.acm.org>]

sjw wrote:
>> "Adam Beneschan" <a...@irvine.com> wrote in message
>> news:c8af7daf-9f00-4dbb-ad0d-9ca65e0a83d6@f18g2000prf.googlegroups.com...
>>
>>> If FpB'Machine_Rounds is FALSE, though, the situation is interesting.
>>> 4.9(38) requires that static expressions get *truncated* toward zero,
>>> as I read it.  But there's no similar requirement for expressions
>>> computed at runtime.

> This is all very weird. Can I point you to my earlier post at
> http://groups.google.com/group/comp.lang.ada/msg/f79a71b9abe7e287
> which (unless I'm deluded) shows GNAT rounding away from zero for
> dynamic values even though 'Machine_Rounds is False!! (and I get the
> same results on Ubuntu 8.04 with GNAT GPL 2008.

I think Beneschan's quote about what the ARM requires when 'Machine_Rounds is 
False explains this. The compiler is truncating for static expressions as 
required, but not for dynamic expressions. Perhaps it's rounding, or perhaps 
taking the value furthest from zero, for dynamic expressions. The ARM doesn't 
seem to require a specific way of converting for dynamic expressions when 
'Machine_Rounds is False.

-- 
Jeff Carter
"You cheesy lot of second-hand electric donkey-bottom biters."
Monty Python & the Holy Grail
14