if test="not(preceding-sibling::address[zip=$lastZip])" : if « XSLT stylesheet « XML Tutorial

1. XML Tutorial
2. XSLT stylesheet
3. if

File: Data.xml

<?xml version="1.0"?>
<addressbook>
  <address>
    <name>
      <title>Ms.</title>
      <first-name>Doris</first-name>
      <last-name>Smith</last-name>
    </name>
    <street>707 Main Way</street>
    <city>New York</city>
    <state>ME</state>
    <zip>00218</zip>
  </address>
  <address>
    <name>
      <first-name>Jane</first-name>
      <last-name>Smith</last-name>
    </name>
    <street>283 First Avenue</street>
    <city>Vancouver</city>
    <state>MA</state>
    <zip>02718</zip>
  </address>
</addressbook>

File: Transform.xslt

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

  <xsl:output method="text" indent="no"/>

  <xsl:variable name="newline">
  <xsl:text></xsl:text>
  </xsl:variable>

  <xsl:template match="/">
    <xsl:text>Addresses sorted by zip code</xsl:text>
    <xsl:value-of select="$newline"/>
    <xsl:for-each select="addressbook/address">
      <xsl:sort select="zip"/>
      <xsl:sort select="name/last-name"/>
      <xsl:sort select="name/first-name"/>
      <xsl:variable name="lastZip" select="zip"/>
      <xsl:if test="not(preceding-sibling::address[zip=$lastZip])">
        <xsl:text>Zip code </xsl:text>
        <xsl:value-of select="zip"/>
        <xsl:text>: </xsl:text>
        <xsl:value-of select="$newline"/>
        <xsl:for-each select="/addressbook/address[zip=$lastZip]">
          <xsl:sort select="name/last-name"/>
          <xsl:sort select="name/first-name"/>
          <xsl:if test="name/title">
            <xsl:value-of select="name/title"/>
            <xsl:text> </xsl:text>
          </xsl:if>
          <xsl:value-of select="name/first-name"/>
          <xsl:text> </xsl:text>
          <xsl:value-of select="name/last-name"/>
          <xsl:value-of select="$newline"/>
          <xsl:value-of select="street"/>
          <xsl:value-of select="$newline"/>
          <xsl:value-of select="$newline"/>
        </xsl:for-each>
      </xsl:if>
    </xsl:for-each>
  </xsl:template>
</xsl:stylesheet>

Output:

Addresses sorted by zip codeZip code 00218: Ms. Doris Smith707 Main WayZip code 02718: Jane Smith283 First Avenue