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Re: Specifying signs when f(0)=0
Vincent Lefevre <vincent@xxxxxxxxxx> wrote:
One that I heard, but haven't checked out thoroughly, is that it is
needed for interval arithmetic. The claim was that the interval
[-0,x] includes true zero, whereas [+0,x] doesn't. I was and am
unconvinced, but would need to study the matter further to be sure.
This would mean that pow(-0, 2) should return -0 when rounding toward
negative.
Yes.
However, if the tests are a problem, enabling traps allows to avoid them.
They are more-or-less deprecated by IEEE 754, IEEE 754R and C99.
Where did you see that?
In those documents. Many implementors read them as forbidding traps,
even as an option, and I have had heated and unsuccessful arguments
pointing out that is not so.
C99, of course, DOES forbid them even as an option in IEEE 754 mode.
So does Java, all the time. Fortran has had to fight to resist the
people who claim that non-stop mode should be mandated.
Regards,
Nick Maclaren,
University of Cambridge Computing Service,
New Museums Site, Pembroke Street, Cambridge CB2 3QH, England.
Email: nmm1@xxxxxxxxx
Tel.: +44 1223 334761 Fax: +44 1223 334679