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Re^5: Converting to number doesn't always work...

by haukex (Bishop)
on Nov 22, 2019 at 13:04 UTC ( #11109063=note: print w/replies, xml ) Need Help??


in reply to Re^4: Converting to number doesn't always work... (updated)
in thread Converting to number doesn't always work...

Yes, I guess I was a little too unspecific in what I wrote: Given a string $x, looks_like_number($x) should accurately report whether the warning will occur.

Note that Scalar::Util::looks_like_number() is a different function. (That is, it doesn't simply wrap the perl API function of the same name ... it does some other stuff as well.)

True, it's a different function - AFAICT, Scalar::Util::looks_like_number just adds get-magic to Perl_looks_like_number in sv.c, which in turn calls Perl_grok_number in numeric.c, if the scalar has a valid string component (SvPOK). And my understanding is that grok_number is the same internal function that is used to inspect strings for their numeric content - see e.g. Perl_sv_2nv_flags in sv.c, which is called by the SvNV macro, and which calls not_a_number to generate the "Argument isn't numeric" warning.

I had done all this research in the past, and perhaps remembered it a little too simplified, thanks for poking me on this :-)

Update: Well, to nitpick: I did write "the exact internal function that Perl uses to check strings", and you didn't give it a string ;-P But "exact" is indeed inaccurate.

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Re^6: Converting to number doesn't always work...
by syphilis (Bishop) on Nov 22, 2019 at 13:31 UTC
    Well, to nitpick: I did write "the exact internal function that Perl uses to check strings"

    Actually, I did pick that up on a subsequent (but not first) reading of your post.
    But I decided to ignore that.... as to do otherwise was of absolutely no advantage to me ;-)

    Cheers,
    Rob

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