use Perl

• make use of the indices of the $tiers (Score:1)

  by danboo (2604) on 2004.04.28 16:25 (#30434) Journal

  The only real innovation is using only one hash, and using the tier indices to avoid the backing up.
  
use strict;
use warnings;

use Data::Dumper;

my $hash = {};

set_multi_level_hash($hash, [qw/ a b c d /], 'potato');

print Dumper $hash;

sub set_multi_level_hash
      {
      my ( $hash, $tiers, $value ) = @_;

      for (0 .. $#$tiers)
            {
            $hash->{$tiers->[$_]} ||= ( $_ == $#$tiers ? $value : {} );
            $hash = $hash->{$tiers->[$_]};
            }
      }


  Reply to This

  • Re:make use of the indices of the $tiers (Score:1)

    by danboo (2604)

    Oops, to be able to change the value, I suppose the first line in the for loop should be split into:
    
    $hash->{$tiers->[$_]} = {} unless exists $hash->{$tiers->[$_]};
$hash->{$tiers->[$_]} = $value if $_ == $#$tiers;

  • Re:make use of the indices of the $tiers (Score:2)

    by brian_d_foy (44)

    Yeah, I thought about something like that, but then I should go through 0..$#$tiers-1, and do the special case for the last value.
    
    Oh well, too late now. It is out of my hands.
    
    Thanks for the code :)
    
    • Re:make use of the indices of the $tiers (Score:2)

      by jhi (318)

      I think one needs to specify what happens in this case:
      
      set_multi_level_hash($h, [qw(a b c)], 42);
      set_multi_level_hash($h, [qw(a b)], 66);
      
      Oops, we just nuked the first value and the whole "subhash".
      
      In other words, is the level of multiness going to stay the same?
      
      Personally, I would either create a class that guards against the multiness changing, or would make the data structure to be an array reference of hash references, keyed off in the array reference on the depth of $tiers (the latter can of course
      • Re:make use of the indices of the $tiers (Score:2)

        by brian_d_foy (44)

        What you are "supposed" to get depends on what your requirements are. In this case, you assign a different value to a hash key, you replace the value, just like you do if you had written it out as "$h->{a}{b} = 42".
        
        I suppose you could create a class to limit operations, but then, you probably would have need ed a lot more time to deliver the code. One of the requirements was "right now". I didn't build in a lot of extra stuff to make variables not be variable.
        
        There is no get_multi_level_hash functio