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Further to my ramblings here about creating a hash that has multiple values per key I have gone the whole hog and written an object to perform this function having been advised that no such object currently exists. I don't think that it is comprehensive enough to be placed on CPAN but I do think that it may be useful to other users so I am posting it here.

Example usage and other details are included in the pod docs at the top of the file. Any constructive suggestions greatly appreciated. Code below:

=head1 NAME

Datastruct::MultiMap

=head1 DESCRIPTION

This object provides a simple front to a hash mapping keys to arrays o
+f
values thus allowing multiple values for a single key.

=head1 AUTHOR

Arun Horne (arun@simbios.net)

=head1 VERSION HISTORY

1.0 - Initial version (27 May 2003)

=head1 USAGE

 use strict;
 use warnings;

 use Datastruct::MultiMap;
 use Data::Dumper;

 # Create a multimap object
 my $map = Datastruct::MultiMap->new();

 # Add some keys
 $map->put('K1','V1');
 $map->put('K1','V2');
 $map->put('K2','V3');
 $map->put('K3','V4');
 print Dumper $map;

 # Get values
 my @values = $map->get('K1');
 print Dumper \@values;

 # Remove keys
 $map->remove('K1');
 print Dumper $map;

 # Can still access as a normal hash if you want
 print join(",", sort keys %$map), "\n";

=cut


package Datastruct::MultiMap;


use strict;
use warnings;


#
# Creates an empty multimap.
#
sub new()
{
  my $class = shift;
  my $self = {};
  bless $self, $class;
  return $self;
}


#
# Stores a (key, value) pair into the map
#
sub put()
{
  my ($self, $key, $value) = @_;
  unless (exists $self->{$key})
  {
    $self->{$key} = [];
  }
  push @{$self->{$key}}, $value;
}


#
# Returns an array of all the values mapped by the specific key
#
sub get()
{
  my ($self, $key) = @_;
  return @{$self->{$key}};
}


#
# Removes all of the values mapped by the specified key.
#
sub remove()
{
  my ($self, $key) = @_;
  delete $self->{$key};
}


# Package must return true
1;
[download]

____________
Arun

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