# File lib/xpath/expression.rb, line 102
      def to_xpath(predicate=nil)
        if @right.is_a?(Literal)
          "#{@left.to_xpath(predicate)}/@#{@right.to_xpath(predicate)}"
        else
          "#{@left.to_xpath(predicate)}/attribute::node()[name(.) = #{@right.to_xpath(predicate)}]"
        end
      end