Boolean true() and false() as strings?

["John E. Simpson" <simpson at polaris dot net>]

A curious thing (well, to me!)... consider this template rule:

<xsl:template match="sales">
   <h2>Regions Selling More than 300 Units:</h2>
   <xsl:for-each select="region">
     <xsl:variable name="units_gt_300">
       <xsl:choose>
         <xsl:when test="number(units) &gt; 300">
           <xsl:value-of select="true()"/>
         </xsl:when>
         <xsl:otherwise>
           <xsl:value-of select="false()"/>
         </xsl:otherwise>
       </xsl:choose>
     </xsl:variable>
     <xsl:if test="$units_gt_300='true'">
       <h3><xsl:value-of select="concat(@name, ' (', units, ' units)')"/></h3>
     </xsl:if>
   </xsl:for-each>
</xsl:template>

Note the assignment of Boolean true() or false() to the variable, and the 
<xsl:if> test. Why can't the latter be simply:

   <xsl:if test="$units_gt_300">

i.e., why the need to test vs. the string value "true"? Does using the 
true() and false() functions in a variable coerce their return values to 
string type rather than their "native" Boolean?

Here's a simple XML doc to run it against:

<sales quarter="2001-01">
   <region name="Northeast">
     <units>374</units>
     <amount>12500.26</amount>
   </region>
   <region name="Southeast">
     <units>512</units>
     <amount>17692</amount>
   </region>
   <region name="Southwest">
     <units>161</units>
     <amount>8349.72</amount>
   </region>
   <region name="Northwest">
     <units>465</units>
     <amount>15239.6</amount>
   </region>
</sales>

(Tested with both Saxon and the Sept. release of IE5.5, btw.)
==========================================================
John E. Simpson               | "Curiosity killed the cat,
http://www.flixml.org         | but for a while I was a
XML Q&A: http://www.xml.com   | suspect." (Steven Wright) 


 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list