Keeping track of an iterator through a nested xsl:for-each

Question

I want to take the following input:

<test>
    <a>
        <b />
        <b />
    </a>
    <a>
        <b />
        <b />
    </a>
</test>

And create the following output using XSLT 2.0:

<items>
    <item num="1">
        <item num="2"/>
        <item num="3"/>
    </item>
    <item num="4">
        <item num="5"/>
        <item num="6"/>
    </item>
</items>

I know this is wrong, but for a starting point, here's my current XSLT:

<xsl:template match="test">
    <items>
        <xsl:for-each select="a">
            <item num="{position()}">
                <xsl:for-each select="b">
                    <item num="{position()}"/>
                </xsl:for-each>
            </item>
        </xsl:for-each>
    </items>
</xsl:template>

This is clearly not the way to do it, because position() only considers elements in the same level. But how would I do this?

Answer 1

This transformation:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

  <xsl:template match="/*">
    <items><xsl:apply-templates/></items>
  </xsl:template>

  <xsl:template match="a|b">
    <xsl:variable name="vNum">
      <xsl:number level="any" count="a|b"/>
    </xsl:variable>
    <item num="{$vNum}">
      <xsl:apply-templates/>
    </item>
  </xsl:template>
</xsl:stylesheet>

when applied on the provided XML document:

<test>
    <a>
        <b />
        <b />
    </a>
    <a>
        <b />
        <b />
    </a>
</test>

produces the wanted, correct result:

<items>
   <item num="1">
      <item num="2"/>
      <item num="3"/>
   </item>
   <item num="4">
      <item num="5"/>
      <item num="6"/>
   </item>
</items>