# Implement a simple queue in terms of a list.
#
# $Id: Queue.pm,v 1.2 2003/04/18 06:10:47 albertel Exp $
#
# Copyright Michigan State University Board of Trustees
#
# This file is part of the LearningOnline Network with CAPA (LON-CAPA).
#
# LON-CAPA is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# LON-CAPA is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with LON-CAPA; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
#
# /home/httpd/html/adm/gpl.txt
#
# http://www.lon-capa.org/
#
=pod
=head1 Queue
An object oriented implementation of a queue data structure. queues
are first in last out data structures.
=head1 Member functions:
=cut
package Queue;
=pod
=head2 new
Construct a new queue.
=cut
sub new {
my $class = shift; # Class name to bless into.
my $self = []; # Our data is a reference to an anon. array.
bless($self, $class); # Type this as an object.
return $self;
}
=pod
=head2 enqueue
Add an element to the tail of the queue.
=cut
sub enqueue {
my $self = shift; # Get object reference.
my $item = shift; # Get the item to enqueue...
push(@$self, $item); # Push the item to the back of the array.
}
=pod
=head2 dequeue
Remove an element from the front of the queue.
=cut
sub dequeue {
my $self = shift; # Get object reference....
return shift @$self; # Remove from the front of the queue.
}
1;
=pod
=head1 Theory
The queue is implemented as an array... enqueue is a thinly disguised
push, and dequeue is a thinly disguised shift. This is probably quite
in efficient for large queues, but should be fine for reasonably sized
queues.
Note that since Perl is a dynamically typed language, queues can
contain objects of any data type and can even be heterogenously typed.
=cut
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