On 6/2/05, Michael Kay <mike(_at_)saxonica(_dot_)com> wrote:
My process needs to take action on the first element in a list of
elements where the logic to determine first is the lowest
numeric value
of the sortorder attribute. I don't believe there is a
one-line way to
do this - I believe the entire list must be sorted, and then the
position of each element after sort compared to determine if
it is first.
Yes. Even in XSLT 2.0 this may be the best approach. 2.0 offers min/max
functions, but they give you the highest/lowest value, not the node having
that value.
Writing a recursive template/function might give you better performance than
sorting (linear rather than n*log(n)).
There is a one-line solution: $x[not($x/@sortorder < @sortorder)] but it's
quite likely to have poor (quadratic) performance.
You could consider using EXSLT math:highest() or math:lowest().
Or I'm sure there's something in Dimitre's box of tricks called FXSL.
Michael Kay
http://www.saxonica.com/
The following FXSL one-liner does the job:
<xsl:sequence select=
"2*f:xsltSort(/*/*/@sortorder/xs:integer(.), f:add(0))[1]"/>
In this case, the "do-something" operation on the minimum item of the
sequence is double-it.
When evaluated against the following source xml:
<t>
<x sortorder="3"/>
<x sortorder="2"/>
<x sortorder="5"/>
<x sortorder="8"/>
<x sortorder="7"/>
<x sortorder="9"/>
<x sortorder="6"/>
<x sortorder="4"/>
<x sortorder="1"/>
<x sortorder="2"/>
</t>
The correct result:
2
is produced.
The f:xsltSort() function is simply a wrapper around the
xsl:perform-sort
instruction. It accepts a list of functions, which are composed to
produce the effect of multiple sort keys. Here's the code of the
function:
<xsl:function name="f:xsltSort" as="item()*">
<xsl:param name="pSeq" as="item()*"/>
<xsl:param name="pCriteria" as="node()*"/>
<xsl:perform-sort select="$pSeq">
<xsl:sort select="f:compose-flist($pCriteria, .)"/>
</xsl:perform-sort>
</xsl:function>
Certainly, in a future refinement I should also either process an
explicitly passed type-argument (e.g. number or text) or find a way to
efficiently determine the common most non-generic type of all items in
a sequence.
Any ideas?
--
Cheers,
Dimitre Novatchev
---------------------------------------
To avoid situations in which you might make mistakes may be the
biggest mistake of all.
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