# File lib/Domain.rb, line 12
        def initialize(values=nil)
            if not (values.nil? or values.kind_of?(Set))
                raise ArgumentError, "Values must be a set!"
            end
            @values = values.nil? ? Set.new : values
            @undoStack = Array.new
        end

# File lib/Domain.rb, line 21
        def <<(value)
            @values << value
        end

# File lib/Domain.rb, line 81
        def ==(domain)
            return false unless domain.kind_of?(Domain)
            (@values == domain.values) and (@undoStack == domain.undoStack)
        end

# File lib/Domain.rb, line 40
        def collect(&block)
            values.collect(&block)
        end

# File lib/Domain.rb, line 26
        def delete(value)
            @values.delete(value)
        end

# File lib/Domain.rb, line 30
        def each
            @values.each { |value|
                yield value
            }
        end

# File lib/Domain.rb, line 44
        def empty?
            @values.empty?
        end

# File lib/Domain.rb, line 73
        def include?(value)
            @values.include?(value)
        end

# File lib/Domain.rb, line 49
        def prune(values)
            if not values.kind_of?(Set)
                values = Set.new([ values ])
            end
            if values.empty?
                return
            end
            @undoStack.push(@values)
            @values -= values
            if @values.empty?
                self.undoPruning
                raise DomainWipeoutException
            end
        end

# File lib/Domain.rb, line 36
        def sort(&block)
            @values.sort(&block)
        end

# File lib/Domain.rb, line 77
        def to_s
            "{" + @values.entries.join(", ") + "}"
        end

# File lib/Domain.rb, line 66
        def undoPruning
            if @undoStack.empty?
                raise UndoStackEmptyException, "No more prunes to undo!"
            end
            @values = @undoStack.pop
        end