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Re: Mystery state (possibly about whether an argument is numeric?) being maintained across calls to a sub

by poj (Priest)
on Jun 15, 2013 at 15:21 UTC ( #1039129=note: print w/ replies, xml ) Need Help??

Comment on Re: Mystery state (possibly about whether an argument is numeric?) being maintained across calls to a sub
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Re^2: Mystery state (possibly about whether an argument is numeric?) being maintained across calls to a sub
by vsespb (Hermit) on Jun 15, 2013 at 18:38 UTC
    Seems no, not related to bitwise ops. Actually yes, this example shows that addition is not affected.
    use Devel::Peek; use strict; no warnings "numeric"; sub xx { my $arg=shift; Dump( $arg ); print "ARG+1=".($arg+1)."\n"; } xx("ff"); xx(7); xx("ff"); __END__ SV = PV(0x729b78) at 0x754ae0 REFCNT = 1 FLAGS = (PADMY,POK,pPOK) PV = 0x747d90 "ff"\0 CUR = 2 LEN = 8 ARG+1=1 SV = PVNV(0x72b5f0) at 0x754ae0 REFCNT = 1 FLAGS = (PADMY,IOK,pIOK) IV = 7 NV = 0 PV = 0x747d90 "ff"\0 CUR = 2 LEN = 8 ARG+1=8 SV = PVNV(0x72b5f0) at 0x754ae0 REFCNT = 1 FLAGS = (PADMY,POK,pPOK) IV = 7 NV = 0 PV = 0x747d90 "ff"\0 CUR = 2 LEN = 8 ARG+1=1

      It's not the operation, it is whether the argument is forced from numeric to string.


      With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
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      From my slightly cargo-culty perspective on what's going on here, I think that bug looks like it - especially given that non-bitwise ops don't seem to show the weirdness, and since nor does putting the constant string in a variable before doing the &:

      use Devel::Peek; use strict; no warnings "numeric"; sub xx { my $arg = shift; my $const = ""; print "(" . ($arg & $const) . ")\n"; } xx("ff"); xx(7); xx("ff");
      This code gives:
      SV = PV(0x100802558) at 0x1008474e0 REFCNT = 1 FLAGS = (PADMY,POK,pPOK) PV = 0x1002074f0 "ff"\0 CUR = 2 LEN = 8 () SV = PVIV(0x100803c58) at 0x1008474e0 REFCNT = 1 FLAGS = (PADMY,IOK,pIOK) IV = 7 PV = 0x1002074f0 "ff"\0 CUR = 2 LEN = 8 (0) SV = PVIV(0x100803c58) at 0x1008474e0 REFCNT = 1 FLAGS = (PADMY,POK,pPOK) IV = 7 PV = 0x1002074f0 "ff"\0 CUR = 2 LEN = 8 ()

        This code gives:

        Not without a call to Dump it doesn't :)

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