Re: Motion P1788/M0006.04_Level_2_Multi-format NO
On 2009-09-08 11:13:05 +0200, Frédéric Goualard wrote:
> John Pryce wrote:
> > Ah yes. I share your concerns. But I don't see that voting no on
> > motion 6 avoids the difficulties.
> >
> > - There are bound to be interval constructors, for instance in a C++
> > "double" version, we surely can't avoid one that looks like
> > interval(double x, double y)
> >
> > - Then you can't avoid the fact that possible calls are
> > interval(Inf, Inf)
> > interval(NaN,3)
> > interval(4,3)
> >
> > The system has to respond to these invalid calls in SOME way.
> > Frédéric: what would YOU have it do?
>
> State that any invalid form is mapped to the empty set, which Motion 6
> seems to forbid (at least for interval(inf, inf)). No exceptional
> behavior, no NaI.
I don't see why Motion 6 would forbid it. Motion 6 introduces here
a Level-1 *notation*. This does not imply anything for interval
constructors (that would be defined at Level 2 essentially): even
though [+oo,+oo] is an invalid notation, one could decide that for
an interval constructor, interval(+inf,+inf) is the empty set.
In any case, NaN does not exist at Level 1. So, interval constructors
may need to be "different" from the notation.
--
Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.org/>
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Work: CR INRIA - computer arithmetic / Arénaire project (LIP, ENS-Lyon)