RE: Using an index with a sorted list of elements

Hugh Dixon wrote:

> I have a number of elements, similar to <element @value/>
> I want to find the element that has the biggest value of "value" less
> than a value $upperBound.
> Eg
> <elements>
> <element value = "10"/>
> <element value = "80"/>
> <element value = "100"/>
> <element value = "5"/>
> </elements>
>
> If $upperBound is 85, I want <element value = "80"/>
> If $upperBound is  7, I want <element value = "5"/>
>
> I am trying to do something like:
> 	<xsl:for-each select="element[$upperBound>./@value][1]">
> 		<xsl:sort data-type="number" select="./@value"
> order="descending"/>
> 			<xsl:value-of select="."/>
> 	</xsl:for-each>

I tried to test your system, but I noticed for a start that you are using
<xsl:value-of select="."> to output the string value of the element which
matches, but ... the elements have no string value because they are empty.
I'm sure in your real data the elements have content! ;-)

Anyway ... a solution:

You could select the element you want with a single xpath expression. You
want the first element, whose value is less than the upperbound, and whose
value is NOT less than the value of the OTHER elements whose values are less
than the upperbound. That is to say:

element[(@value &lt; $upperBound)][not(@value &lt; ../element[(@value &lt;
$upperBound)]/@value)]

Or equivalently, using a variable to refer to the bounded set of the nodes <
upperBound:

<xsl:variable
	name="bounded"
	select="element[(@value &lt; $upperBound)]"
/>
<xsl:copy-of
	select="$bounded[not(@value &lt; $bounded/@value)][1]"
/>

Cheers!

Con


 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list