nysus has asked for the wisdom of the Perl Monks concerning the following question:

I've got an array of anonymous hashes. Each hash has a string for a key. Each value of this hash is an anonymous hash keyed with numerical keys. I'm trying to use Dumper to print this data structure. I have the $Data::Dumper::Sortkey variable set to this subroutine: 
sub hash_sort {
  my ($hash) = @_;
  return [
  (sort {$a <=> $b} keys %$hash)
   ];
}

[download]
The problem is that this throws errors like 'Argument "apwu749_d5" isn't numeric in sort at update_settings.pl line 87' because it's trying to sort the hash keyed with a string numerically. What's the best way to modify this subroutine so it works for all kinds of hashes?

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Re: Using Data::Dumpers Sortkeys subroutine
by almut (Canon) on Nov 27, 2008 at 07:18 UTC
    "apwu749_d5" isn't numeric in sort

    Maybe cmp instead of <=> ?

    (some sample data together with the expected (sorted) output might help...)

[reply]
[d/l]
[select]
      Here is some sample data: 
      $VAR3 = {
          'apwu749_d5' => {
                            '1' => 'anonymous user',
                            '13' => 'Elected Officer',
                            '17' => 'APWU Staff',
                            '2' => 'authenticated user',
                            '3' => 'member',
                            '4' => 'web site committee',
                            '5' => 'administrator',
                            '9' => 'Shop Steward'
                          }
        };
$VAR4 = {
          'atu1700_drupal5' => {
                                 '1' => 'anonymous user',
                                 '2' => 'authenticated user',
                                 '3' => 'administrator',
                                 '4' => 'member',
                                 '5' => 'superuser',
                                 '6' => 'web site committee',
                                 '7' => 'steward',
                                 '9' => 'Executive Board Member'
                               }
        };

      [download]
      Notice how the numeric keys are sorted 1, 13, 17, 2, 3... in the first hash. That's what I'm trying to correct.

      $PM = "Perl Monk's";
      $MCF = "Most Clueless Friar Abbot Bishop Pontiff Deacon";
      $nysus = $PM . $MCF;
      Click here if you love Perl Monks

[reply]
[d/l]
      Right, but what's the best way to make this subroutine intelligent enough to distinguish between a has with strings as keys and a hash with numeric values. The problem is Data::Dumper just blindly uses this subroutine for all hashes. I need to build intelligence into it so it knows which sort algorithm to use.

      $PM = "Perl Monk's";
      $MCF = "Most Clueless Friar Abbot Bishop Pontiff Deacon";
      $nysus = $PM . $MCF;
      Click here if you love Perl Monks

[reply]
[reply]
Re: Using Data::Dumpers Sortkeys subroutine
by nysus (Parson) on Nov 27, 2008 at 07:37 UTC
    I solved it with this less-than-ideal hack which works for this special case: 
     84 sub hash_sort {
 85   my ($hash) = @_;
 86   if (ref %$hash != 'REF') {
 87     return [
 88       (sort {$a <=> $b} keys %$hash)
 89     ];
 90   } else {
 91     return [
 92       (sort {$a cmp $b} keys %$hash)
 93     ];
 94   }
 95 }

    [download]
    It tests to see if the value of the has is a reference to the anonymous hash. If not, it sorts it numerically, otherwise it gets sorted alphabetically. What would be a more robust way of solving this?

    $PM = "Perl Monk's";
    $MCF = "Most Clueless Friar Abbot Bishop Pontiff Deacon";
    $nysus = $PM . $MCF;
    Click here if you love Perl Monks

[reply]
[d/l]
      What would be a more robust way of solving this?

      I think natural sort - as Corion suggested - would fit the bill quite well: 

      use Data::Dumper;
use Sort::Naturally;

$Data::Dumper::Sortkeys = sub {
  my ($hash) = @_;
  return [ nsort( keys %$hash ) ];
};

      [download]
[reply]
[d/l]
        Hmm, that results in an error: 
        Bizarre copy of ARRAY in return at /usr/lib/perl/5.8/Data/Dumper.pm li
+ne 511, <FH> line 130.
Segmentation fault

        [download]

        $PM = "Perl Monk's";
        $MCF = "Most Clueless Friar Abbot Bishop Pontiff Deacon";
        $nysus = $PM . $MCF;
        Click here if you love Perl Monks

[reply]
[d/l]

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