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from FAQ

Scalar::Util (distributed with 5.8) provides access to perl's internal function looks_like_number for determining whether a variable looks like a number.

update

despite older discussions recommending that way I do have problems on my system:

DB<243> $nan=sin(9**9**9) => "nan" DB<244> looks_like_number($nan) => 8704 DB<245> $nan eq "nan" => 1 DB<246> Scalar::Util::looks_like_number($nan) => 36

I know that NaN is plattform/C-compiler depended, so better test which way works.

update

according to perlop#Equality Operators

DB<106> $nan=sin(9**9**9) => "nan" DB<107> print "NaN support here" if $nan != $nan => 1 NaN support here DB<108>

Cheers Rolf

( addicted to the Perl Programming Language)


In reply to Re^3: Perl returns NaN after addition by LanX
in thread Perl returns NaN after addition by pimperator

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