Re: map a list - segfault

The block that caused the segfault doesn't work the way you think it does, because of precedence:

perl -MO=Deparse -e '               
(@n=(1,2) && ($n[1],$n[0]));                  
(@n=(1,2) && ($n[1],$n[0]));                   
(@n=(1,2) && ($n[1],$n[0]));                   
'
@n = ('???', 2) && ($n[1], $n[0]);
@n = ('???', 2) && ($n[1], $n[0]);
@n = ('???', 2) && ($n[1], $n[0]);
[download]

Using 'and' instead of && would work, or an extra set of parens.

perl -MO=Deparse -e '
(@n=(1,2) && ($n[1],$n[0]));
((@n=(1,2)) && ($n[1],$n[0]));
(@n=(1,2) and ($n[1],$n[0]));  
'
@n = ('???', 2) && ($n[1], $n[0]);
$n[1], $n[0] if @n = (1, 2);
$n[1], $n[0] if @n = (1, 2);
[download]

As for the segfault itself, I don't grok why it breaks but Devel::Peek gives a hint:

perl -MDevel::Peek -le '
(@n=(1,2) && ($n[1],$n[0])); print Dump \@n;
(@n=(1,2) && ($n[1],$n[0])); print Dump \@n;'
SV = RV(0x3c02b018) at 0x3c0062dc
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x3c011718
  SV = PVAV(0x3c0084dc) at 0x3c011718
    REFCNT = 2
    FLAGS = ()
    IV = 0
    NV = 0
    ARRAY = 0x3c02a4f0
    FILL = 1
    MAX = 3
    ARYLEN = 0x0
    FLAGS = (REAL)
    Elt No. 0
    SV = NULL(0x0) at 0x3c006168
      REFCNT = 1
      FLAGS = ()
    Elt No. 1
    SV = NULL(0x0) at 0x3c006264
      REFCNT = 1
      FLAGS = ()

SV = RV(0x3c02b018) at 0x3c0062dc
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x3c011718
  SV = PVAV(0x3c0084dc) at 0x3c011718
    REFCNT = 2
    FLAGS = ()
    IV = 0
    NV = 0
    ARRAY = 0x3c02a4f0
    FILL = 1
    MAX = 3
    ARYLEN = 0x0
    FLAGS = (REAL)
    Elt No. 0
    SV = UNKNOWN(0xff) (0x0) at 0x3c006168
      REFCNT = 1
      FLAGS = ()
    Elt No. 1
    SV = UNKNOWN(0xff) (0x0) at 0x3c006264
      REFCNT = 1
      FLAGS = ()
[download]

Note that the array entries changed from :

SV = NULL(0x0) at 0x3c006168
[download]

To:

SV = UNKNOWN(0xff) (0x0) at 0x3c006168
[download]

Comment on Re: map a list - segfault Select or Download Code


Just another Perl shrine
	PerlMonks