XSLT example template that returns boolean

In XSLT you can create templates that act as boolean functions.

<xsl:template match="/">
  <!-- create variable named cat to store boolean value -->
  <xsl:variable name="cat">
      <xsl:call-template name="HasCat"/>
  </xsl:variable>

  <xsl:when test="$cat= 'true'" >
      <!-- do something because it has a child element named cat -->
  </xsl:when>
</xsl:template>


<xsl:template name="HasCat">
  <xsl:choose>
      <xsl:when test="count(descendant-or-self::*[contains(local-name(), 'Cat')]) > 0">
          <xsl:value-of select="true()"/>
      </xsl:when>
      <xsl:otherwise>
          <xsl:value-of select="false()"/>
      </xsl:otherwise>
  </xsl:choose>
</xsl:template>