Re: YES P1788/M0029.02:Level3-InterfaceOnly, *BUT*
Baker wrote:
> On 12/29/2011 05:00 PM, Michel Hack wrote:
> > Lee Winter wrote:
> >> I believe the exclusion of overflows of the same sign is unnecessary
> >> for the interchange format.
> >
> > I suppose you mean two infinities of the same sign. Infinities may
> > indeed be the result of containing overflow, but they can also simply
> > mean "unbounded". Decorations should tell these cases apart. (In 754
> > it is the overflow flag that does the job -- unfortunately globally.)
>
> Although we have been discussing this for a while, the distinction
> is still not clear to me, at least on a philosophical level.
Remember my claim that there are two philosophically different interpretations
of intervals: (a) imprecise single values, and (b) ranges of multiple values.
In case (a) the concept of unbounded only arises when dividing by an imprecise
value which could be zero -- and perhaps an exception should be noted. In
case (b) a range may be naturally unbounded on one or both sides.
> Can't an overflow be viewed simply as a "round to unbounded?"
Yes, but only because we have no other way to preserve containment when
using traditional floating-point representations. There are in fact
representations that avoid overflow, such as level-index representations.
Michel.
---Sent: 2011-12-31 00:12:42 UTC