Simple. Allow (+inf,+inf) as an
interval (understanding that it is not a point interval). Then it
encloses +inf.
If you don't like that, you could decide
the result is NaI. One of the possible meanings of NaI is "The
result should be (-Inf,-Inf) or (+Inf,+Inf) but we decided to disallow
those so we're using NaI."
- Ian Toronto
IBM Lab 8200 Warden D2-445 905-413-3411
----- Forwarded by Ian
McIntosh/Toronto/IBM on 10/09/2009 03:00 PM -----
John Pryce <j.d.pryce@xxxxxxxxxxxx>
10/09/2009 01:42 PM
Please respond to
John Pryce <j.d.pryce@xxxxxxxxxxxx>
To
Ian McIntosh/Toronto/IBM@IBMCA
cc
Subject
Re: Request for motion [Fwd: Input from
IFIP WG 2.5 to IEEE Interval Standards Working Group]
Arnold
On 10 Sep 2009, at 12:25, Arnold Neumaier wrote:
> Dan Zuras Intervals wrote:
>>
If we are to pursue this at this time, please include accurate
>>
versions of all of sum, dot product, sum of squares, &
sum of
>>
absolute values for all supported precisions.
> ...
> I think only interval-valued results for noninterval inputs should
> be provided by the standard. Then there are no problems.
>
> If some element is NaN or two terms in the sum are +inf and -inf,
> the result should be the empty set; otherwise the tightest enclosing
> interval of the exact result should be returned.
Am I missing something? Suppose we implement as you say, "interval-
valued results for noninterval inputs", and just ONE term of the sum
is, say, +inf, the rest being finite numbers. Then the result is
+inf, but since P1788 is based on the reals, there is no interval
that encloses this. What to do?