<?xml version="1.0"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<?cocoon-process type="xslt"?>

<!-- Defining and Calling the Factorial Function in XSLT  -->
<!-- Harold Boley "boley@informatik.uni-kl.de" 2000-12-05 -->

<!-- A speparate file factorial-main.xml provides specific arguments -->

  <!-- call factorial on selected integer argument n -->
  <xsl:template match="/arguments/a1">
    <html>
      <head>
        <title>factorial(<xsl:value-of select="."/>)</title>
      </head>
      <body>
        <xsl:call-template name="factorial">
          <xsl:with-param name="n" select="."/>
        </xsl:call-template>
      </body>
    </html>
  </xsl:template>

  <!-- define factorial(n) recursively using factor variable -->
  <xsl:template name="factorial">
    <xsl:param name="n"/>
    <xsl:choose>
      <xsl:when test="$n = 0">1</xsl:when>            <!-- factorial(0) = 1 -->
      <xsl:when test="$n > 0">                        <!-- factorial(n) =   -->
        <xsl:variable name="factor">
          <xsl:call-template name="factorial">
            <xsl:with-param name="n" select="$n - 1"/>
          </xsl:call-template>
        </xsl:variable>
        <xsl:value-of select="$n * $factor"/>         <!-- n*factorial(n-1) -->
      </xsl:when>
    </xsl:choose>
  </xsl:template>

</xsl:stylesheet>

