Re: A new perl {cough} feature?

This seems to be a bug in Data::Dumper. With the perl debugger (before the grep, thanks tye):

main::(-:1):    my @matrix = ();
  DB<1> n
main::(-:2):    $matrix[2]->[3] = "What's goin' on?";
  DB<1> n
main::(-:3):    grep {/Huh?/}@$_ for @matrix;
  DB<1> print @matrix
ARRAY(0x8103f2c)
  DB<2> x @matrix
0  undef
1  undef
2  ARRAY(0x8103f2c)
   0  empty slot
   1  empty slot
   2  empty slot
   3  'What\'s goin\' on?'
  DB<3>
[download]

With Data::Denter:

Before grep:
@
    ?
    ?
    @
        ?
        ?
        ?
        What's goin on?

After grep:
@
    @
    @
    @
        ?
        ?
        ?
        What's goin on?
[download]

... indicating undef (?) before the grep, as normal, and empty array refs (@) after the grep, as normal due to autovivification upon array dereference. Only Data::Dumper seems to get it wrong, or at least what seems to be wrong.

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Re: Re: A new perl {cough} feature? by Anarion (Hermit) on Feb 17, 2002 at 16:32 UTC
Yes, but try this one: `use Data::Denter; my @matrix = (); $matrix[2]->[3]= "What's goin on?"; print "Before grep:\n", Denter(\@matrix); #print grep{ /Huh?/ }@$_ for @matrix; print map { grep{ /Huh?/ }@$_ } @matrix; print "\nAfter grep:\n", Denter(\@matrix);` [download] Where is the bug then in Data::Dumper or in Data::Denter or in map, grep, for or autovivification? $anarion=\$anarion; s==q^QBY_^=,$_^=$[x7,print	[reply] [d/l]
Re: Re: A new perl {cough} feature? by belg4mit (Prior) on Feb 17, 2002 at 17:28 UTC
It's not unreasonable that it is a Data::Dumper flaw. Recently I was using Data::Dumper on some not so complex structures and some of the values it output were array-refs (where no array-ref ought to live) i.e. it output the scalar form of the array-ref, not even an evalable form. `-- perl -pe "s/\b;([st])/'\1/mg"`	[reply]
(tye)Re: A new perl {cough} feature? by tye (Sage) on Feb 18, 2002 at 14:16 UTC
Quick clarification: Note that the first set of output is from before grep gets run. It is the grep that autovivifies those empty array references. - tye (but my friends call me "Tye")	[reply]