Re: YES P1788/M0029.02:Level3-InterfaceOnly, *BUT*
Lee Winter replied:
> > 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".
>
> What IEEE-754 operation produces an "unbounded" result from numeric
> inputs? AFAIK there are none.
Division of finite by zero yields infinity without raising overflow.
This is arithmetic in R* -- extended reals. It is true that 754 does
not have a concept of "unbounded", as it deals with individual numbers.
A given number is finite or infinite, but only a set can be unbounded.
In any case, we are talking about 1788, which does have the concept
of unbounded. Intervals ARE sets of finite numbers. (Cf. Motion 3)
> > Decorations should tell these cases apart. (In 754
> > it is the overflow flag that does the job -- unfortunately globally.)
>
> By the term "overflow flag" do you mean the overflow exception?
Setting the overflow flag is the result of the 754 default action for
the overflow exception. The flag and the exception are related but
not the same. But I could just as well have said "overflow exception"
because a non-default handler could in fact set a local flag that is
attached to the result, just as 1788 decorations are. In fact, some
numeric packages do just that (e.g. Mike Cowlishaw's DecNumber).
As for Siegfried Rump's Dec 5 posting: I did not get it. I lost access
to stds-1788 from Nov 23 through Nov 28 and have no posts dated Nov 23
through Dec 2, but lots of Dec 3 posts; no Dec 4 but a couple of Dec 5.
I had asked whether I had missed anything, but got no reply, and the
listserver's index function does not work. I see now that the archive
serves that function (but requires web access), and found Siegfried's
posting; I can also check what I missed...
Michel.
---Sent: 2011-12-30 14:59:19 UTC