merging distinct valued nodes in a node stream using xsl - xslt

Question

I want to merge distinct valued nodes from a list of nodes using xsl. Whenever distinct value violets it creates a new tag.
Input:
<PAGE>
<T>1</T>
<T>2</T>
<T>3</T>
<T>2</T>
<T>1</T>
<T>3</T>
<T>3</T>
</PAGE>
Output:
<PAGE>
<T>1,2,3</T>
<T>2,1,3</T>
<T>3</T>
</PAGE>
Suppose first three nodes are having value 1,2 and 3 and the the fourth node is having value 2, then we have to merge first three as all values are unique. Then next merging will start from fourth node. Now suppose fifth node is again having value 2. Then in out only fourth node will be there as the next node value is same. Like wise I have to keep on merging nodes as long as the values are unique. For example if the node value stream is 1,2,2,3,4,1,1,3,3, the the Output will be 12,2341,13,3.IN merged node unique values can exist.
Please suggest me a XSL to do that

Answer 1

The following stylesheet:
XSLT 1.0
<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:strip-space elements="*"/>
<xsl:template match="PAGE">
<xsl:copy>
<xsl:apply-templates select="T[1]"/>
</xsl:copy>
</xsl:template>
<xsl:template match="T">
<xsl:param name="prev-string" select="','"/>
<xsl:variable name="next-string" select="concat($prev-string, ., ',')" />
<xsl:variable name="next-node" select="following-sibling::T[1]" />
<xsl:choose>
<xsl:when test="contains($next-string, concat(',', $next-node, ',')) or not($next-node)">
<!-- End of chain: create an element and output the accumulated string ... -->
<xsl:copy>
<xsl:value-of select="substring($next-string, 2, string-length($next-string) - 2)"/>
</xsl:copy>
<!-- ... and start a new chain -->
<xsl:apply-templates select="$next-node"/>
</xsl:when>
<xsl:otherwise>
<!-- Continue the current chain: add the current value to the accumulated values -->
<xsl:apply-templates select="$next-node">
<xsl:with-param name="prev-string" select="$next-string"/>
</xsl:apply-templates>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
</xsl:stylesheet>
when applied to your example input, will return:
<?xml version="1.0" encoding="UTF-8"?>
<PAGE>
<T>1,2,3</T>
<T>2,1,3</T>
<T>3</T>
</PAGE>
Note:
It is assumed that values do not contain the separating character
(comma in this example);
Although this employs tail-recursion (partially, anyway), a large document could easily send your processor into stack overflow.