# File lib/xml/xpath.rb, line 778
    def round
      f = @value
      unless f.nan? or f.infinite? then
        if f >= 0.0 then
          @value = f.round.to_f
        elsif f - f.truncate >= -0.5 then
          @value = f.ceil.to_f
        else
          @value = f.floor.to_f
        end
      end
      self
    end