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### Re: How do I create/detect/handle Infinity?

by shmem (Chancellor)
 on Jul 25, 2009 at 11:04 UTC ( #783158=note: print w/replies, xml ) Need Help??

in reply to How do I create/detect/handle Infinity?

Creating Inf/NaN:

```use Devel::Peek;
\$inf = (~@~)**(~@~);
\$nan = \$inf / \$inf;
Dump \$_ for \$inf, \$nan;
__END__
SV = NV(0x9e15f84) at 0x9dfc11c
REFCNT = 2
FLAGS = (NOK,pNOK)
NV = inf
SV = NV(0x9e15f9c) at 0x9dfc59c
REFCNT = 2
FLAGS = (NOK,pNOK)
NV = nan

Detecting Inf/NaN: since they are numeric values, Inf and NaN can be tested for with the numeric equality/inequality operators == and !=. For Inf, greater and less also work.

Handling: not useful ;-)

Devel::Peek

Replies are listed 'Best First'.
Re: Answer: How do I create/detect/handle Infinity?
by ysth (Canon) on Jul 26, 2009 at 06:26 UTC
NaN doesn't test as == anything, even another NaN.
NaN doesn't test as == anything, even another NaN.

I was wondering:
```unless (\$x <= \$inf) { print "\\$x is definitely a NaN\n" }
else { print "\\$x is definitely NOT a NaN\n" }
Is that reliable ? ... assuming, of course, that \$inf is in fact + infinity, and that there are no bugs present.
Seems to me that ought to be good enough.

Cheers,
Rob
Yes. Other ways:
```\$isnan = (\$x != \$x);
\$isnan = ! defined(\$x <=> 0);

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