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Re: mixed content grouping by whitespace

Subject: Re: mixed content grouping by whitespace
From: David Carlisle <davidc@xxxxxxxxx>
Date: Tue, 13 Apr 2010 18:09:54 +0100
Re:  mixed content grouping by whitespace
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.


$ 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 name="y" select="0,1,2,0,3,4"/>

<xsl:template name="main">

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

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

<xsl:for-each-group select="$x/*" group-starting-with="h2">
<xsl:copy-of select="current-group()"/>

<!-- error
<xsl:for-each-group select="$y" group-starting-with="0">
<xsl:copy-of select="current-group()"/>


<!-- 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>


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