# Copyright (c) 2009 bivio Software, Inc.  All Rights Reserved.
#
# Visit http://www.bivio.biz for more info.
# 
# This library is free software; you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as
# published by the Free Software Foundation; either version 2.1 of the
# License, or (at your option) any later version.
# 
# This library 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
# Lesser General Public License for more details.
# 
# You should have received a copy of the GNU Lesser General Public
# License along with this library;  If not, you may get a copy from:
# http://www.opensource.org/licenses/lgpl-license.html
# 
# $Id: NullBoolean.pm,v 1.1 2009/12/05 05:17:37 nagler Exp $
package Bivio::Type::NullBoolean;
use strict;
use Bivio::Base 'Type.Boolean';

our($VERSION) = sprintf('%d.%02d', q$Revision: 1.1 $ =~ /\d+/g);

sub from_literal {
    my($self, $value) = @_;
    return undef
	unless defined($value);
    return shift->SUPER::from_literal(@_);
}

1;