On 29.03.2016 10:46, Michael Müller-Hillebrand mmh(_at_)docufy(_dot_)de wrote:
I think you need to write a recursive function to detect cycles in a graph, and
XPath 2.0 does not have sufficient power for this. It can of course be done in
XSLT or XQuery. It can possibly be done in XPath 3.0, though because XPath 3.0
functions are anonymous, recursion is tricky.
Well, how would that kind of trick look like?
This is my version of a recursive function for Roger's problem (assuming there can be
multiple elements <for-more-info>):
<xsl:function name="my:CycleFound" as="xs:boolean">
<xsl:param name="this" as="element()?"/>
<xsl:param name="visited" as="xs:string*"/>
<xsl:variable name="refId" select="$this/for-more-info/@idref"
as="xs:string*"/>
<xsl:variable name="refTgt" select="$this/../item[@id = $refId]"
as="element()*"/>
<xsl:sequence select="
if (not(exists($refTgt))) then false()
else if ($refId = $visited) then true()
else some $e in $refTgt satisfies my:CycleFound($e, ($visited, $e/@id))
"/>
</xsl:function>
I have no idea how one would have to handle this using XPath 3… any suggestions?
Dimitre has an article on using two anonymous function together with
"let", to implement the recursion:
https://dnovatchev.wordpress.com/2012/10/15/recursion-with-anonymous-inline-functions-in-xpath-3-0-2/
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