While writing a template, I came across a situation in Microsoft's
evaluation of my XSLT where, for a given XPath expression, count() of
that nodeset was not equal to last() of that nodeset.  I can't find
anything in my books, Jeni Tennison's e.g., that explains this
behavior.  I've reduced the code to the following trivial example.

My XML input is

<?xml version="1.0" encoding="UTF-8"?>
<root>
	<Students>
		<row>
			<Name>Bob</Name>
		</row>
		<row>
			<Name>Joe</Name>
		</row>
	</Students>
</root>

and my XSLT is

<?xml version="1.0" encoding="UTF-8"?>

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

	<xsl:output method="xml" media-type="text/xml" encoding="UTF-8" />

	<xsl:preserve-space elements="*" />

	<xsl:variable name="countNames" select="count(/root/Students/row/
Name)" />

	<xsl:variable name="allNames" select="/root/Students/row/Name" />

	<xsl:variable name="firstName" select="/root/Students/row/
Name[position() = 1]" />
	<xsl:variable name="lastName" select="/root/Students/row/
Name[position() = last()]" />

	<xsl:variable name="firstName2" select="(/root/Students/row/Name)
[position() = 1]" />
	<xsl:variable name="lastName2" select="(/root/Students/row/Name)
[position() = last()]" />

	<xsl:template match="/">

		<Students>

			<Count>
				<xsl:value-of select="$countNames" />
			</Count>

			<AllNames>
				<xsl:copy-of select="$allNames"/>
			</AllNames>

			<Case1>
				<First>
					<xsl:value-of select="$firstName" />
				</First>
				<Last>
					<xsl:value-of select="$lastName" />
				</Last>
			</Case1>

			<Case2>
				<First>
					<xsl:value-of select="$firstName2" />
				</First>
				<Last>
					<xsl:value-of select="$lastName2" />
				</Last>
			</Case2>

		</Students>

	</xsl:template>

</xsl:stylesheet>

The XML output from this transform is

<?xml version="1.0" encoding="utf-8"?>
<Students>
	<Count>2</Count>
	<AllNames>
		<Name>Bob</Name>
		<Name>Joe</Name>
	</AllNames>
	<Case1>
		<First>Bob</First>
		<Last>Bob</Last>
	</Case1>
	<Case2>
		<First>Bob</First>
		<Last>Joe</Last>
	</Case2>
</Students>

Note that the XPath /root/Students/row/Name yielded a nodeset of two
names, as shown by the value of both Count and AllNames.  But the
expression
/root/Students/row/Name[position() = last()] did not evaluate to the
second name.  Even more strangely, /root/Students/row/Name[1] and /
root/Students/row/Name[last()] yielded the same result, even though
the nodeset in question contains two names.

Can anyone explain this strange behavior?  Thanks.