Re: [xsl] Finding Unique Nodes

Subject: Re: [xsl] Finding Unique Nodes
From: Peter Davis <pdavis152@xxxxxxxxx>
Date: Mon, 1 Apr 2002 22:24:41 -0800
On Monday 01 April 2002 21:04, Ivan Pedruzzi wrote:
> <?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"/>
>   <xsl:template match="/">
>     <list>
>     <xsl:for-each select="list/item">
>     <xsl:sort select="list/item"/>

This sort requires that "/list/item/list/item" exists, "list/item" is 
relative to the "list/item" that was selected in the for-each.  To do what I 
think you are trying to do, you want:

<xsl:sort select="."/>

>           <xsl:if test="not(following-sibling::item = .)">

The test for following-sibling::item is applied on the source document, *not* 
the document after it has been sorted.  So the sorting will not affect 
anything.  Also, this is the same as:

not(./following-sibling::item = .)

which is always true, because a node is never a following-sibling of itself.  
Therefore, the next line (<item><xsl:value-of select="."/></item>) will 
always be executed.

>                 <item><xsl:value-of select="."/></item>
>       </xsl:if>
>     </xsl:for-each>
>     </list>
>   </xsl:template>
> </xsl:stylesheet>

There is a way to select unique nodes with following-sibling, but I prefer 
the key()-based solution myself.

<xsl:template match="item">
  <xsl:if test="not(following-sibling::item[string(.) = string(current())])">
    <xsl:copy-of select="."/>
  </xsl:if>
</xsl:template>

This doesn't easily allow for counting the number of unique nodes (it only 
lets you output their values).  Not to mention that it doesn't scale with 
large documents, which is why you should do something like this:

<xsl:key name="item" match="item" use="string(.)"/>

<xsl:template match="/">
  <xsl:text>Unique items: </xsl:text>
  <xsl:value-of
    select="count(list/item[count(key('item', string(.)) | .) = 1])"/>
</xsl:template>

Look up "Muenchian method" for info on why this works.

-- 
Peter Davis
The Angels want to wear my red shoes.
		-- E. Costello

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