Re: [xsl] mixed content grouping by whitespace

[David Carlisle <davidc@xxxxxxxxx>]

On 13/04/2010 17:45, G. Ken Holman wrote:

> As I see it and have no problems remembering it:
>
> group-by and group-adjacent are based on values,
> group-starting-with and group-ending-with are based on names.

yes but that is still arbitrary. the difference betwen group-by and 
group-starting with is (to me) mainly that in the former you re-order 
the items to put them in groups, but in the latter you do not, and you 
just partition the input sequence without re-ordering. Why should the 
choice between ordering and not ordering be tied to names/values?
> ...
> I'm not really sure what you are trying to say there, David. And in what
> you are trying to say are you accommodating the feature of using a
> sequence in group-by= in order to place a single population member into
> more than one group simultaneously? I need to include a running example
> of that in the classroom to help convey that concept to students.

The following has two variables, one holding nodes and the other 
numbers. I can group the nodes into heading or not heading with almost 
identical code to grouping the numbers into even or odd. Just use 
appropriate predicates.

However if i don't want to re-order things get harder. For nodes I can 
make a group starting with each heading, but how do you easily partition 
the integers into groups starting at each 0?
If group-starting-with took a boolean expression rather than a pattern 
it would be a lot easier, see the commented out code at the end.

David


$ saxon9 -it main grp.xsl
<?xml version="1.0" encoding="UTF-8"?>
<grouping-nodes>
   <group>
      <h2>heading 1</h2>
      <h2>heading 2</h2>
   </group>
   <group>
      <p> para 1.1</p>
      <p> para 1.2</p>
      <p> para 2.1</p>
      <p> para 2.2</p>
   </group>
</grouping-nodes>
<grouping-items>
   <group>0 2 0 4</group>
   <group>1 3</group>
</grouping-items>
<grouping-nodes-without-reordering>
   <group>
      <h2>heading 1</h2>
      <p> para 1.1</p>
      <p> para 1.2</p>
   </group>
   <group>
      <h2>heading 2</h2>
      <p> para 2.1</p>
      <p> para 2.2</p>
   </group>
</grouping-nodes-without-reordering>






<xsl:stylesheet version="2.0" 
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";>

<xsl:output indent="yes"/>

<xsl:variable name="x">
<h2>heading 1</h2>
<p> para 1.1</p>
<p> para 1.2</p>
<h2>heading 2</h2>
<p> para 2.1</p>
<p> para 2.2</p>
</xsl:variable>

<xsl:variable name="y" select="0,1,2,0,3,4"/>

<xsl:template name="main">

<grouping-nodes>
<xsl:for-each-group select="$x/*" group-by="exists(self::h2)">
<group>
<xsl:copy-of select="current-group()"/>
</group>
</xsl:for-each-group>
</grouping-nodes>

<grouping-items>
<xsl:for-each-group select="$y" group-by=". mod 2 = 0">
<group>
<xsl:copy-of select="current-group()"/>
</group>
</xsl:for-each-group>
</grouping-items>



<grouping-nodes-without-reordering>
<xsl:for-each-group select="$x/*" group-starting-with="h2">
<group>
<xsl:copy-of select="current-group()"/>
</group>
</xsl:for-each-group>
</grouping-nodes-without-reordering>

<!-- error
<grouping-nodes-without-reordering>
<xsl:for-each-group select="$y" group-starting-with="0">
<group>
<xsl:copy-of select="current-group()"/>
</group>
</xsl:for-each-group>
</grouping-nodes-without-reordering>

-->

<!-- david C-s ideal world The above woul dnot be an error and
group-starting-with would take an expression not a match, and the group 
would start whenever the expression was true.
so to do nodes you would have to do self::h2 as in the group-by example
(or with exists() for extra clarity rather than relying on implict 
boolean conversion)


<grouping-nodes-without-reordering>
<xsl:for-each-group select="$x/*" group-starting-with="exists(self::h2)">
<group>
<xsl:copy-of select="current-group()"/>
</group>
</xsl:for-each-group>
</grouping-nodes-without-reordering>


-->
</xsl:template>


</xsl:stylesheet>

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