# $Id: Cycle.pm,v 1.6 2002/12/17 20:19:16 comdog Exp $ package Tie::Cycle; use strict; use vars qw( $VERSION ); $VERSION = sprintf "%d.%02d", q$Revision: 1.6 $ =~ m/ (\d+) \. (\d+) /xg; sub TIESCALAR { my $class = shift; my $list_ref = shift; my @shallow_copy = map { $_ } @$list_ref; return unless UNIVERSAL::isa( $list_ref, 'ARRAY' ); return unless @$list_ref > 1; my $self = [ 0, scalar @shallow_copy, \@shallow_copy ]; bless $self, $class; } sub FETCH { my $self = shift; my $index = $$self[0]++; $$self[0] %= $self->[1]; return $self->[2]->[ $index ]; } sub STORE { my $self = shift; my $list_ref = shift; return unless ref $list_ref eq ref []; return unless @$list_ref > 1; $self = [ 0, scalar @$list_ref, $list_ref ]; } sub reset { my $self = shift; $$self[0] = 0; } sub previous { my $self = shift; my $index = $$self[0] - 1; $$self[0] %= $self->[1]; return $self->[2]->[ $index ]; } sub next { my $self = shift; my $index = $$self[0] + 1; $$self[0] %= $self->[1]; return $self->[2]->[ $index ]; } "Tie::Cycle"; __END__ =head1 NAME Tie::Cycle - Cycle through a list of values via a scalar. =head1 SYNOPSIS use Tie::Cycle; tie my $cycle, 'Tie::Cycle', [ qw( FFFFFF 000000 FFFF00 ) ]; print $cycle; # FFFFFF print $cycle; # 000000 print $cycle; # FFFF00 print $cycle; # FFFFFF back to the beginning (tied $cycle)->reset; # back to the beginning =head1 DESCRIPTION You use C<Tie::Cycle> to go through a list over and over again. Once you get to the end of the list, you go back to the beginning. You don't have to worry about any of this since the magic of tie does that for you. The tie takes an array reference as its third argument. The tie should succeed unless the argument is not an array reference or the referenced array contains fewer than two elements. During the tie, this module makes a shallow copy of the array reference. If the array reference contains references, and those references are changed after the tie, the elements of the cycle will change as well. See the included test.pl script for an example of this effect. =head1 OBJECT METHODS You can call methods on the underlying object (which you access with tied().). =over 4 =item reset Roll the iterator back to the starting position. The next access will give the first element in the list. =item previous Give the previous element. This does not affect the current position. =item next Give the next element. This does not affect the current position. You can peek at the next element if you like. =back =head1 SOURCE AVAILABILITY This source is part of a SourceForge project which always has the latest sources in CVS, as well as all of the previous releases. https://sourceforge.net/projects/brian-d-foy/ If, for some reason, I disappear from the world, one of the other members of the project can shepherd this module appropriately. =head1 AUTHOR brian d foy, E<lt>bdfoy@cpan.orgE<gt> =head1 COPYRIGHT and LICENSE Copyright 2000, brian d foy, All rights reserved. This software is available under the same terms as perl. =cut