XPath expression to convert XSD enumerations into a r

Hi Folks,

I have an XSD simpleType with enumeration values:

<xsd:simpleType name="RunwayLightingType">
  <xsd:restriction base="xsd:string">
   <xsd:enumeration value="1"/>
   <xsd:enumeration value="2"/>
   <xsd:enumeration value="3"/>
   <xsd:enumeration value="4"/>
   <xsd:enumeration value="5"/>
   <xsd:enumeration value="6"/>
   <xsd:enumeration value="7"/>
   <xsd:enumeration value="8"/>
   <xsd:enumeration value="9"/>
   <xsd:enumeration value="10"/>
   <xsd:enumeration value="11"/>
   <xsd:enumeration value="12"/>
  </xsd:restriction>
 </xsd:simpleType>

I want to turn the values into a regex such that the longest value (not the
biggest value, the string longest value) is listed first:

12|11|10|9|8|7|6|5|4|3|2|1

Seems like a simple problem, right? Should have a simple solution, right?

Well, I devised a solution, but it sure ain't simple.

string-join(for $i in reverse(sort(xs:restriction/xs:enumeration, (),
function($enum) {string-length($enum/@value )})) return $i/@value, '|')

Is there is a simpler XPath expression to solve this problem?

/Roger