http://www.perlmonks.org?node_id=852509


in reply to Re^2: Numification of strings
in thread Numification of strings

in Perl, everything is a string until used in a numeric context

I don't think that is true.

In your example you put quotation-marks around the value, so little surprise that you end up with a string...

Consider this:

use Devel::Peek;

my $a = "1";
my $b = 2;

print Dump($a);
print Dump($b);

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This produces:

SV = PV(0x98c9700) at 0x98ea3f8
  REFCNT = 1
  FLAGS = (PADMY,POK,pPOK)
  PV = 0x98e6368 "1"\0
  CUR = 1
  LEN = 4
SV = IV(0x98ea474) at 0x98ea478
  REFCNT = 1
  FLAGS = (PADMY,IOK,pIOK)
  IV = 2

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As you can see $a is a string "PV", while $b is an int "IV", even thought it was never used in an numeric context.

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Re^4: Numification of strings
by ww (Archbishop) on Aug 02, 2010 at 18:27 UTC
    "As you can see $a is a string "PV", while $b is an int "IV", even thought it was never used in an numeric context."

    If you mean what I think you mean -- that $b is an int BECAUSE it was never used in a numeric content -- I think you're wrong, morgon: $b IS an IV, because it was instantiated that way... as an integer, without quotes that would have made it a string.

    Update: Maybe I have the code tags right... at last.

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[d/l]
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      If you mean what I think you mean ...

      :-)

      I meant to disprove the theory that a value becomes an int only after being used in a numeric context by showing an example in which a value is only instantiated (and never used in a numeric context), yet still is numeric.

      Or less convoluted: I probably meant what you said.

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Re^4: Numification of strings
by Marshall (Canon) on Aug 02, 2010 at 18:11 UTC
    I updated my post above:
    re: Also of note is that in Perl, a string that looks like a number is still a string until used in a numeric context. Feel free to suggest alternate wording for this sentence.

    These leading zero situations can happen when reading DB files of various formats, say from a split() or whatever.

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