Re: Re-orderable keyed access structure?

[CombatSquirrel]

Maybe this does what you want:

#!perl

use strict;
use warnings;

my (@array, %hash);

sub push_item {
   # push_item(key => value)
   return 0
      if defined $hash{$_[0]};
   push @array, [$_[1], $_[0], scalar @array];
   $hash{$_[0]} = $array[-1];
   return 1;
}

sub swap_array {
   # swap_array(index1, index2)
   @array[$_[0], $_[1]] = @array[$_[1], $_[0]];
   ($array[$_[0]]->[2], $array[$_[1]]->[2])
      = ($array[$_[1]]->[2], $array[$_[0]]->[2]);
}

sub get_array_pos_by_key {
   # get_array_pos_by_key(key)
   return undef
      unless exists $hash{$_[0]};
   $hash{$_[0]}->[2];
}

sub get_hash_key_by_index {
   # get_hash_key_by_index(index)
   return undef
      unless $_[0] < @array;
   $array[$_[0]]->[1];
}

# populate

push_item('foo'    => 'bar');
push_item('joe'    => 'banana');
push_item('foe'    => 'friend');
push_item('gin'    => 'tonic');
push_item('ice'    => 'age');

print get_array_pos_by_key('gin'), "\n";
print get_array_pos_by_key('joe'), "\n";
print $hash{'gin'}->[0], ' ', $hash{'joe'}->[0], "\n";
print $array[3]->[0], ' ', $array[1]->[0], "\n";
swap_array(get_array_pos_by_key('gin'), get_array_pos_by_key('joe'));
print get_array_pos_by_key('gin'), "\n";
print get_array_pos_by_key('joe'), "\n";
print $hash{'gin'}->[0], ' ', $hash{'joe'}->[0], "\n";
print $array[3]->[0], ' ', $array[1]->[0], "\n";

I'm in a bit of a hurry now, but it maintains both a hash and an array of array references whith item, array index and hash key in it. The data structures don't have to be moved, which is an advantage for large data structures, but more than one data item has to be modified when items are swapped. I hope the code explains the rest.
Hope this helped.
CombatSquirrel.