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Re^3: Perl returns NaN after addition

by LanX (Saint)
on Oct 17, 2013 at 01:09 UTC ( [id://1058574]=note: print w/replies, xml ) Need Help??


in reply to Re^2: Perl returns NaN after addition
in thread Perl returns NaN after addition

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)

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