Re: Sort mechanics problems with objects and potentially contradicting comparisons (would cause infinite loop)

But strangely, the code below which shifts the first parameter magically DWIMmed by getting the right object.

I don't believe you.

perl -e'
   use strict;
   use warnings;

   use Data::Dumper qw( Dumper );

   sub _DBsort4create {
      my $obj = shift;
      print(Dumper($obj));
      0
  }

   my $csvQ = { x => 123, y => 456 };
   for my $csvq ( sort _DBsort4create keys %$csvQ ) {
   }
'
$VAR1 = undef;
[download]

If it does happen to return the right object, you are modifying a stack you shouldn't be modifying, which should lead to dire repercussions.

Comment on Re: Sort mechanics problems with objects and potentially contradicting comparisons (would cause infinite loop) Download Code

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Re^2: Sort mechanics problems with objects and potentially contradicting comparisons (would cause infinite loop) by anonymized user 468275 (Curate) on Jun 02, 2016 at 07:47 UTC
In your example no object has been blessed One world, one people	[reply]
Re^3: Sort mechanics problems with objects and potentially contradicting comparisons (would cause infinite loop) by ikegami (Patriarch) on Jun 02, 2016 at 15:03 UTC
Do you really think that adding `my $o = bless({});` is going to make a difference? Why? Did you try it?	[reply] [d/l]
Re^4: Sort mechanics problems with objects and potentially contradicting comparisons (would cause infinite loop) by anonymized user 468275 (Curate) on Jun 06, 2016 at 15:54 UTC
It was already blessed in the constructor and all methods including the sort routine are in the same class. I don't understand why you are so surprised under the circumstances. Also, why would they call it bless if it had no magic about it? However, I do expect it has something to do with the inheritance magic as I can't reproduce it in an inherticance free case. One world, one people	[reply]
Re^5: Sort mechanics problems with objects and potentially contradicting comparisons (would cause infinite loop) by ikegami (Patriarch) on Jun 08, 2016 at 15:12 UTC
Re^2: Sort mechanics problems with objects and potentially contradicting comparisons (would cause infinite loop) by Anonymous Monk on Jun 02, 2016 at 16:31 UTC
You're right, ik, the code will not work as the OP claims. @_ does not get set when _DBsort4create is called by sort; it's left holding the argument list of the sub that called sort. `sub compare { my $x = shift; print "\$a = $a, \$b = $b, \$x = $x, \@_ = @_\n"; $a cmp $b; } sub test { sort compare 'z','a','b' } my @z = test('foo', 'bar', 'baz'); print "\@z = @z\n"; output: $a = z, $b = a, $x = foo, @_ = bar baz $a = a, $b = b, $x = bar, @_ = baz $a = b, $b = z, $x = baz, @_ = @z = a b z` [download]	[reply] [d/l]