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Re^2: nans, infs, and vomit

by syphilis (Bishop)
on Sep 01, 2008 at 14:17 UTC ( #708228=note: print w/replies, xml ) Need Help??


in reply to Re: nans, infs, and vomit
in thread nans, infs, and vomit

No IEEE rationale

In a nutshell then ... what is it that inspired this notion that the strings "nan"/"inf" should actually become nans/infs when used numerically ? Was it something that the perl porters dreamed up all by themselves ?

It sure has been giving me some headaches lately. (Actually, it's the lack of uniformity across different operating systems that's the problem. If they all did the same thing, no matter how distasteful that "same thing" was, life would be much simpler :-)

Cheers,
Rob

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Re^3: nans, infs, and vomit
by Anonymous Monk on Sep 01, 2008 at 14:28 UTC
      http://www.perl.com/doc/FMTEYEWTK/is_numeric.html

      Yes - that puts this behaviour into context. When any string is put into numeric context, perl just hands that string over to the underlying C implementation of atof(), and we're then at the mercy of what that function does with the string it has been passed.

      On some systems, atof turns the strings 'nan' and 'inf' into actual nans and infinities. On other implementations of atof,a nan/inf will never result from a call to atof - irrespective of what string it receives. This is not a very convenient situation ... but we can't blame perl for differences in the underlying C libraries.

      Thanks for the link Anonymous Monk.

      Cheers,
      Rob

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