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)

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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!
[reply]
      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

      [download]

      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>

      [download]

      Cheers Rolf

      ( addicted to the Perl Programming Language)

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