#
# This file contains the Ruby code from Program 5.1 of
# "Data Structures and Algorithms
# with Object-Oriented Design Patterns in Ruby"
# by Bruno R. Preiss.
#
# Copyright (c) 2004 by Bruno R. Preiss, P.Eng.  All rights reserved.
#
# http://www.brpreiss.com/books/opus8/programs/pgm05_01.txt
#
class AbstractObject < ::Object

    def initialize
        super
    end

    include ::Comparable

    def <=>(obj)
	if is_a?(obj.type)
            return compareTo(obj)
        elsif obj.is_a?(type)
            return -obj.compareTo(self)
        else
	    return type.name <=> obj.type.name
	end
    end

    abstractmethod :compareTo

    protected :compareTo

end