Re: [xsl] Is it possible to group by name() ?

[Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>]

Frank,

At 04:54 PM 9/17/2002, you wrote:
> I would appreciate some help on this. I have an XML that looks like this:
>
> <n0>
>         <n1>
>                 <a>text</a>
>                 <b>text</b>
>                 <c>text</c>
>         </n1>
>         <n1>
>                 <a>text</a>
>                 <c>text</c>
>         </n1>
>         <n1>
>                 <a>text</a>
>                 <b>text</b>
>                 <d>text</d>
>         </n1>
> </n0>
>
> And what I would like to have is a list of the different nodes inside n1
> nodes.
> In the example above, the result should be: a,b,c,d.
>
> Is it possible to do something like this ?
> <xsl:key name="groupbyname" match="/n0/n1/*" use="name()"/>
>
> And then use the muenchian method ? But how ?

You're right on track.

When using the Muenchian method, remember it works by doing two things. 
First, grouping, which you have down (your key does this). Then, 
de-duplicating by picking one node from each group -- using it to fire off 
processing the whole group if necessary (in your case it's not). Once 
you've mastered the two steps, it's only a matter of deciding how you want 
to traverse your nodes to get to them.

So you could do:

<xsl:for-each select="/n0/n1/*">
  <!-- iterates over all the candidate nodes -->
  <xsl:if test="count(.|key('groupbyname', name())[1]) = 1">
    <!-- throws away all but the first of each group -->
    <xsl:value-of select="name()"/>
    <!-- outputs the name you want -->
  </xsl:if>
</xsl:for-each>

Similarly, an entire stylesheet could look like:

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

<xsl:output method="text"/>

<xsl:strip-space elements="*"/>
<!-- cleans things up a bit -->

<xsl:key name="groupbyname" match="/n0/n1/*" use="name()"/>

<xsl:template match="/n0/n1/*[count(.|key('groupbyname', name())[1]) = 1]">
  <!-- puts the selection logic into a template match -->
  <xsl:value-of select="concat(name(), '&#xA;')"/>
  <!-- inserting an extra line break for clarity -->
</xsl:template>

<xsl:template match="text()">
  <!-- suppress text nodes as uninteresting -->
</xsl:template>

</xsl:stylesheet>

Fun, huh?

Cheers,
Wendell


======================================================================
Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
Mulberry Technologies, Inc.                http://www.mulberrytech.com
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Suite 207                                          Phone: 301/315-9631
Rockville, MD  20850                                 Fax: 301/315-8285
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