On 21 November 2017 at 13:08, Costello, Roger L. costello@xxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> David Carlisle wrote:
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>> why?
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> What I mean is that this expression:
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> $sequence-extended/item = ($sequence/item, $item)
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> returns false when $sequence is empty (and the other variables have the values I described).
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> /Roger
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to give a reply of more than one word, the xpath you suggest returns
true not false on both the examples you give:

$ saxon9 -it:test seq1.xsl
<?xml version="1.0" encoding="UTF-8"?>

test1: true


test2: true


where seq1.xsl is



<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">



<xsl:template name="test">
<!--
    Suppose that $sequence-extended has this value:
    -->
<xsl:variable name="sequence-extended" as="element()">
    <sequence>
        <item>A</item>
        <item>B</item>
    </sequence>
</xsl:variable>

<!--
And $sequence has this value:
-->
<xsl:variable name="sequence" as="element()">
    <sequence>
        <item>A</item>
    </sequence>
</xsl:variable>

<!--
And $item has this value:
-->
<xsl:variable name="item" as="element()">
    <item>B</item>
</xsl:variable>

test1: <xsl:value-of select="$sequence-extended/item =
($sequence/item, $item)"/>


<!--
But, the XPath expression fails when $sequence is empty:
-->
<xsl:variable name="sequence" as="element()">
    <sequence/>
</xsl:variable>
<!--
And $sequence-extended has a single item:
-->
<xsl:variable name="sequence-extended" as="element()">
    <sequence>
        <item>A</item>
    </sequence>
</xsl:variable>

<!--
    And $item is:
-->
<xsl:variable name="item" as="element()">
    <item>A</item>
</xsl:variable>


test2: <xsl:value-of select="$sequence-extended/item =
($sequence/item, $item)"/>

</xsl:template>

</xsl:stylesheet>