XSLT, 2nd Edition

Implementing Lookup Tables with <xsl:function>

Using document('') to implement lookup tables is a workable approach, but we can simplify things with an XSLT function. With a function, we can invoke getStateName() to resolve a state abbreviation to a state name; that’s much simpler than invoking document('')/*/states:name[@abbrev=current()] or something similar. Here’s how our function looks:

<xsl:function name="states:getStateName" as="xs:string">
  <xsl:param name="abbr" as="xs:string"/>
  <xsl:variable name="abbreviations" as="xs:string*"
    select="'AL', 'AK', 'AS', 'AZ', 'AR', 'CA', 'CO', 'CT',
<!-- state abbreviations removed for brevity -->
            'WV', 'WI', 'WY'"/>
  <xsl:variable name="stateNames" as="xs:string*"
    select="'Alabama', 'Alaska', 'American Samoa','Arizona', 
<!-- state names removed for brevity -->
            'West Virginia', 'Wisconsin', 'Wyoming'"/>
  <xsl:variable name="index"
    select="if (count(index-of($abbreviations, $abbr)) gt 0) 
            then subsequence(index-of($abbreviations, $abbr), 1, 1)
            else 0"/>
  <xsl:value-of 
    select="if ($index gt 0)
            then string(subsequence($stateNames, $index, 1))
            else ''"/>
</xsl:function>

Our function takes a single string, a state abbreviation, as a parameter, and it returns a single string. It uses two variables to store our data; $abbreviations is a sequence of all state abbreviations, and $stateNames is a sequence of all state names. The positions of items in the two sequences match each other. If the abbreviation passed to the function matches the fifth item in ...