deep-equal()

Description

deep-equal() compares two sequences item by item. Two sequences are deeply equal if they have the same length and each pair of corresponding items is deeply equal. For atomic values, deep equality uses the same comparison as = with type promotion. For nodes, deep equality means the nodes have the same kind, name, and — recursively — the same children, attributes, and text content.

The optional collation argument controls string comparison. When omitted, the default collation is used. This makes deep-equal() suitable for locale-aware comparisons of mixed sequences containing strings.

deep-equal() never raises an error for incompatible types: comparing an integer to a string returns false rather than a type error, which distinguishes it from the = operator.

Parameters

Return value

xs:boolean — true if the sequences are deeply equal, false otherwise.

Examples

Comparing two element subtrees

Input XML:

<?xml version="1.0" encoding="UTF-8"?>
<root>
  <a><x>1</x><y>2</y></a>
  <b><x>1</x><y>2</y></b>
  <c><x>1</x><y>3</y></c>
</root>

Stylesheet:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="2.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="xml" indent="yes"/>

  <xsl:template match="/root">
    <results>
      <ab><xsl:value-of select="deep-equal(a, b)"/></ab>
      <ac><xsl:value-of select="deep-equal(a, c)"/></ac>
    </results>
  </xsl:template>
</xsl:stylesheet>

Output:

<results>
  <ab>true</ab>
  <ac>false</ac>
</results>

Comparing sequences of atomic values

Stylesheet:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="2.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xsl:output method="text"/>

  <xsl:template match="/">
    <xsl:variable name="s1" select="(1, 2, 3)"/>
    <xsl:variable name="s2" select="(1, 2, 3)"/>
    <xsl:variable name="s3" select="(1, 2, 4)"/>
    <xsl:value-of select="deep-equal($s1, $s2)"/><xsl:text>&#10;</xsl:text>
    <xsl:value-of select="deep-equal($s1, $s3)"/><xsl:text>&#10;</xsl:text>
  </xsl:template>
</xsl:stylesheet>

Output:

true
false

Notes

• deep-equal() compares attributes regardless of document order for element nodes. Two elements with the same attributes in a different order are still deeply equal.
• Namespace nodes, processing instructions, and comments are included in the comparison when they are present in the node’s children.
• The function is particularly useful in unit tests and validation stylesheets where you need to assert that a transformation produced an expected XML structure.
• An empty sequence is deeply equal only to another empty sequence.

See also

• empty()
• count()
• exactly-one()