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Re: Perl returns NaN after addition

by LanX (Saint)
on Oct 17, 2013 at 00:45 UTC ( [id://1058572]=note: print w/replies, xml ) Need Help??


in reply to Perl returns NaN after addition

Thanks to my good relation to the NSA I was able to break into your computer and look at the data you are hiding from us. :)

It looks like you had a non-numeric variable in the data file!

> so how would I test for that?

stop reading the file as soon as you get NaN. Print the line number '$.' and dump line and column with Data::Dumper

BTW: did you use warnings?

Cheers Rolf

( addicted to the Perl Programming Language)

Replies are listed 'Best First'.
Re^2: Perl returns NaN after addition
by pimperator (Acolyte) on Oct 17, 2013 at 01:03 UTC
    What is the regex for testing if a variable is NaN? and warnings did not spit out anything. thanks!
      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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