def parse_float attr_name, xpath
      v = parse_value xpath
      v = v.to_f if v.respond_to?(:to_f)
      send("#{attr_name}=", v)
    end
def parse_float attr_name, xpath
      v = parse_value xpath
      v = v.to_f if v.respond_to?(:to_f)
      send("#{attr_name}=", v)
    end
parse, convert and assign node text to float