XSLT, 2nd Edition

Implementation

We’ll define four global parameters for our stylesheet:

<xsl:param name="i"         select="1"/>
<xsl:param name="increment" select="1"/>
<xsl:param name="operator"  select="'<='"/>
<xsl:param name="testValue" select="10"/>

The default values defined here correspond to the C++ or Java statement for (i = 1; i <= 10; i++). We also have a match="/" template that invokes our for loop processor:

<xsl:template match="/">
  <xsl:call-template name="for-loop">
    <xsl:with-param name="i"         select="$i"/>
    <xsl:with-param name="increment" select="$increment"/>
    <xsl:with-param name="operator"  select="$operator"/>
    <xsl:with-param name="testValue" select="$testValue"/>
  </xsl:call-template>
</xsl:template>

In the for-loop template, our first task is to determine whether the condition is true. We do this by calculating a boolean value with several <xsl:when> elements, each of which looks like the one below:

    <xsl:variable name="testPassed">
      <xsl:choose>
        <xsl:when test="$operator = '!='">
          <xsl:if test="$i != $testValue">
            <xsl:text>true</xsl:text>
          </xsl:if>
        </xsl:when>
        ...
    </xsl:variable>

If the variable $testPassed is true, the for-loop template calls itself again. Before the <xsl:call-template> instruction, we can put whatever logic we want. For our sample, we simply write the current value of $i to the output.