sum() sums all numbers in selected nodes. : sum « XSLT stylesheet « XML Tutorial

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2. XSLT stylesheet
3. sum

File: Data.xml
<?xml version="1.0" encoding="utf-8"?>
<data>
    <number>1</number>
    <number>3</number>
    <number>4</number>
    <number>17</number>
    <number>8</number>
    <number>11</number>
</data>
File: Transform.xslt

<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet
      version="1.0"
      xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="/">
      <xsl:for-each select="//number">
        <xsl:value-of select="."/>
        <xsl:choose>
          <xsl:when test="position()=last()">
            <xsl:text> = </xsl:text>
          </xsl:when>
          <xsl:otherwise>
            <xsl:text> + </xsl:text>
          </xsl:otherwise>
        </xsl:choose>
      </xsl:for-each>
      <xsl:value-of select="sum(//number)"/>
    </xsl:template>
</xsl:stylesheet>

Output:

<?xml version="1.0" encoding="UTF-8"?>1 + 3 + 4 + 17 + 8 + 11 = 44