# File lib/xpath/expression.rb, line 54
      def to_xpath(predicate=nil)
        if @expressions.length == 1
          "#{@left.to_xpath(predicate)}//#{@expressions.first.to_xpath(predicate)}"
        elsif @expressions.length > 1
          "#{@left.to_xpath(predicate)}//*[#{@expressions.map { |e| "self::#{e.to_xpath(predicate)}" }.join(" | ")}]"
        else
          "#{@left.to_xpath(predicate)}//*"
        end
      end