precalculating node-set via copy-of and accessing ancestors (XSLT 1.0) - xslt

Question

I want to precalculate a subtree of nodes in an source XML, and the process them seperately (because I want the subset to be processed in different ways), and access some values from ancestors.
simple example
<numbers count="5">
<number value="1"/>
<number value="2"/>
<number value="3"/>
<number value="4"/>
<number value="5"/>
</numbers>
and lets say I have an xslt (MSXML) to extract the even nodes somehow
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:msxsl="urn:schemas-microsoft-com:xslt" exclude-result-prefixes="msxsl"
>
<xsl:output method="xml" indent="yes"/>
<xsl:template match="/">
<evens>
<xsl:for-each select="numbers/number">
<xsl:choose>
<xsl:when test="#value mod 2 = 0">
<even>
<xsl:attribute name="count">
<xsl:value-of select="../#count"/>
</xsl:attribute>
<xsl:attribute name="value">
<xsl:value-of select="#value"/>
</xsl:attribute>
</even>
</xsl:when>
</xsl:choose>
</xsl:for-each>
</evens>
</xsl:template>
</xsl:stylesheet>
and we get..
<evens>
<even count="5" value="2" />
<even count="5" value="4" />
</evens>
nice...
but how can I seperate the filtering from the processing so something like...
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:msxsl="urn:schemas-microsoft-com:xslt" exclude-result-prefixes="msxsl"
>
<xsl:output method="xml" indent="yes"/>
<xsl:template name="calculateNodes">
<xsl:for-each select="numbers/number">
<xsl:choose>
<xsl:when test="#value mod 2 = 0">
<xsl:copy-of select="."/>
</xsl:when>
</xsl:choose>
</xsl:for-each>
</xsl:template>
<xsl:template match="/">
<xsl:variable name="nodes">
<xsl:call-template name="calculateNodes"/>
</xsl:variable>
<evens>
<xsl:for-each select="msxsl:node-set($nodes)/number">
<even>
<xsl:attribute name="count">
<xsl:value-of select="../#count"/>
</xsl:attribute>
<xsl:attribute name="value">
<xsl:value-of select="#value"/>
</xsl:attribute>
</even>
</xsl:for-each>
</evens>
</xsl:template>
</xsl:stylesheet>
this gives.
<evens>
<even count="" value="2" />
<even count="" value="4" />
</evens>
so...the ancestors arent copied.
Is there an idiomatic way to get out of this?

Answer 1

A copied node exists on its own, outside of the original tree. In your example, the parent of number is the $nodes variable, which does not have any attributes.
Why don't you do simply:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
<xsl:template match="/numbers">
<xsl:variable name="nodes" select="number[#value mod 2 = 1]"/>
<evens>
<xsl:for-each select="$nodes">
<even count="{../#count}" value="{#value}"/>
</xsl:for-each>
</evens>
</xsl:template>
</xsl:stylesheet>
This way you have a variable containing a reference to the original nodes, instead of a copy. Then you also have access to the original parent. And the content of the variable is a node-set; you don't need to convert it.

Answer 2

this seems to work
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:msxsl="urn:schemas-microsoft-com:xslt" exclude-result-prefixes="msxsl"
>
<xsl:output method="xml" indent="yes"/>
<xsl:template name="calculateNodes">
<xsl:for-each select="numbers/number">
<xsl:choose>
<xsl:when test="#value mod 2 = 0">
<numberWrapper>
<xsl:attribute name="count">
<xsl:value-of select="../#count"/>
</xsl:attribute>
<xsl:copy-of select="."/>
</numberWrapper>
</xsl:when>
</xsl:choose>
</xsl:for-each>
</xsl:template>
<xsl:template match="/">
<xsl:variable name="nodes">
<xsl:call-template name="calculateNodes"/>
</xsl:variable>
<evens>
<xsl:for-each select="msxsl:node-set($nodes)/numberWrapper">
<even>
<xsl:attribute name="count">
<xsl:value-of select="#count"/>
</xsl:attribute>
<xsl:attribute name="value">
<xsl:value-of select="number/#value"/>
</xsl:attribute>
</even>
</xsl:for-each>
</evens>
</xsl:template>
</xsl:stylesheet>