[xsl] Re: set:intersection oddity

["Dimitre Novatchev" <dnovatchev@xxxxxxxxx>]

"John Sharp" <jsharp@xxxxxx> wrote in message
news:3EFDED78.290F7F48@xxxxxxxxx
> Hello, I was attempting to use the set:intersection function
> from http://exslt.org/sets.  The examples showing the intersection
> of cities with letters 'i' and 'e' work as given. However the
> following does not work - INTERSECT1 is always empty.

As it should be.

You do not understand the definition of set:intersection().

The specification of this function says: "The set:intersection function
returns a node set comprising the nodes that are within both the node sets
passed as arguments to it. "

http://www.exslt.org/set/functions/intersection/index.html

That is, the equality-operation used in defining set:intersection() has
node-identity semantics and not node-value semantics.

>   <INTERSECT1>
>     <xsl:copy-of select="set:intersection($data,$rules)"/>
>   </INTERSECT1>

In your example below, the nodes in the $data and $rules are two distinct
root nodes, they are not the same node, therefore

set:intersection($data, $rules) must return the empty node-set.

>   <INTERSECT2>
>     <xsl:copy-of select="set:intersection($data,$data)"/>
>   </INTERSECT2>

This intersects the root node contained in $data with itself -- therefore
this is equivalent to:

    <xsl:copy-of select="$data"/>

and must output the whole tree contained in $data, which is exactly what you
got.

>   <INTERSECT3>
>     <xsl:copy-of select="$data[count(. | $rules) != count( $rules)]"/>
>   </INTERSECT3>
>

Here you want to xsl-copy  all the nodes of $data (and this is just its root
node) that are not identical to some of the nodes (just the root node) of
$rules. As these are two distinct root nodes, the above is again equivalent
to:

    <xsl:copy-of select="$data"/>

An example, which will "work" is the following:

  <xsl:copy-of select="set:intersection($rules/*, $rules/*[position() mod 2
= 0])"/>

This will intersect all the children of the root node with the ones that
have an even position() and will xsl:copy-of the element $rules/*[2]


Note to confused readers -- the OP has specified version="1.1" on the
xsl:stylesheet instruction, this is why we do not need to convert RTFs to
regular trees.


=====
Cheers,

Dimitre Novatchev.
http://fxsl.sourceforge.net/ -- the home of FXSL



>
> <xsl:stylesheet
>   xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
>   xmlns:saxon="http://saxon.sf.net/";
>   xmlns:set="http://exslt.org/sets";
>   extension-element-prefixes="set saxon"
> version="1.1">
>
> <xsl:template match="/">
>
>   <xsl:variable name="data">
>     <Type>PMT</Type>
>     <Type>FUNC</Type>
>   </xsl:variable>
>
>   <xsl:variable name="rules">
>     <Type>PMT</Type>
>     <Type>DC_PARA</Type>
>     <Type>FUNC</Type>
>   </xsl:variable>
>
>
>   <INTERSECT1>
>     <xsl:copy-of select="set:intersection($data,$rules)"/>
>   </INTERSECT1>
>
>   <INTERSECT2>
>     <xsl:copy-of select="set:intersection($data,$data)"/>
>   </INTERSECT2>
>
>   <INTERSECT3>
>     <xsl:copy-of select="$data[count(. | $rules) != count( $rules)]"/>
>   </INTERSECT3>
>
> </xsl:template>
>
>
> Here's the output:-
>
> <?xml version="1.0" encoding="UTF-8"?>
> <INTERSECT1/>
> <INTERSECT2>
>    <Type>PMT</Type>
>    <Type>FUNC</Type>
> </INTERSECT2>
> <INTERSECT3>
>    <Type>PMT</Type>
>    <Type>FUNC</Type>
> </INTERSECT3>Execution time: 336 milliseconds
>
>
> If I run the exslt web page example, it runs fine.
>
> Kind regards,John.
>
>  XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list
>
>




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