On 08.04.2010 17:50, Michael Müller-Hillebrand wrote:
Am 08.04.2010 um 16:09 schrieb Michael Kay:
It seems to me that you first want to create (or imagine) a graph: in your
example there are arcs k->o, o->p, p->c, a->b, b->c, etc.
Then you want to look for cycles in this graph. If any cycles exist, there
is no solution to your problem.
Thanks Michael, I guess I have to finally understand the graph stuff. I will
turn to the example in the 4th edition p.251 ff. for a starter.
Am 08.04.2010 um 16:47 schrieb Imsieke, Gerrit, le-tex:
[... cool, ready-made example ...]
Does that make sense?
If I include<o/> at the other position, i.e.,
<seq><k/><f/><z/><o/></seq>,
I receive "Too many nested function calls. May be due to infinite recursion."
as expected.
Gerrit, I am at early stages to understand the algorithm. The function counts
the maximum number of preceding siblings on any available path and uses this as
a sort key. This is some sort of creating a graph, backtracing to the
beginning... which is what Michael suggested, isn't it.
Thanks a lot for the most valuable input!
I need a result and the inconsistency report, so the user can fix the input. I
will be looking into stopping the infinite recursion somehow.
Here's a modified XSLT that will complain about <o/> if you include it
inconsistently (<seq><k/><f/><z/><o/></seq>):
---------------------------------------
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet
xmlns:xs="http://www.w3.org/2001/XMLSchema";
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
xmlns:my="URN:my"
version="2.0" >
<xsl:output
method="xml"
indent="yes"
/>
<xsl:template match="/">
<xsl:apply-templates />
</xsl:template>
<xsl:template match="foo">
<xsl:copy>
<xsl:for-each-group select="seq/*" group-by="name(.)" >
<xsl:sort select="my:sortkey(., ())"/>
<xsl:element name="{current-grouping-key()}" />
</xsl:for-each-group>
</xsl:copy>
</xsl:template>
<xsl:function name="my:sortkey" as="xs:integer">
<xsl:param name="input" as="element(*)" />
<xsl:param name="previously-seen" as="xs:string*" />
<xsl:if test="name($input) = $previously-seen">
<xsl:message terminate="yes">Element <xsl:value-of
select="name($input)"/> doesn't seem to occur at an deterministic position.
</xsl:message>
</xsl:if>
<xsl:variable name="preceding-siblings"
select="$input/../../seq/*[name() =
name($input)]/preceding-sibling::*[1]" as="element(*)*" />
<xsl:variable name="seen"
select="distinct-values(($previously-seen, name($input)))" />
<xsl:sequence select="(max(for $ps in $preceding-siblings return
my:sortkey($ps, $seen)) + 1, 1)[1]"/>
</xsl:function>
</xsl:stylesheet>
---------------------------------------
No time to explain how it works now. Later!
Gerrit
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