Re: As simple as it is now, I am still against motion 24.03...
On 2011-06-13 14:21:29 +0100, John Pryce wrote:
> Vincent wrote:
> > Note that if x is a real, then [x,x] is a valid interval.
> > As [x,x] must be supported, then it also makes sense to support just x
> > as input. ... if not in tight mode, do you still require that f(x) and
> > f([x,x]) should return the same interval? ...
>
> I think so. Any problem in that?
No, but then this should be specified in the standard.
Even in floating-point, on the same platform, with the same compiler
and the same compilation options, f(x) doesn't always return the same
value in practice. You can see my slides on
http://www.vinc17.net/research/slides/sieste2010.pdf
(Slide 11 and the following ones). IMHO, P1788 should avoid that.
Note: due to maintainance, my web server may be temporarily
unavailable in the next few days.
> >> I suggest that on 754-compliant systems the operations be
> > Why 754-compliant systems only?
>
> Because "formatOf" is explicitly provided in 754-2008, so on such
> systems this comes for free, if I read the standard correctly.
But this is optional. And conversely, non-754 systems can provide
such functions.
> >> parameterised by the output interval format, like a 754 "formatOf"
> >> operation, and that interval format shall be of infsup type only. So
> >> one can input data of any FP format having the *same radix* as the
> >> output format.
> > I think that different input formats (whether in the same radix or
> > not) should be optional (and not forbidden). Perhaps recommended for
> > the same radix.
>
> Sorry, yes, I didn't mean "forbidden" (and "not permitted", below),
> just not required.
OK.
--
Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / Arénaire project (LIP, ENS-Lyon)