Standard XPath expression for the intersection of two node sets (Was: RE: How can I test if an node included in a nodeset)

[Dimitre Novatchev <dnovatchev at yahoo dot com>]

Michael Kay is the person, who discovered the XPath expression for the
intersection of two node-sets. Therefore, there's no need for a
node-set intersection extension function.

You can find this in http://p2p.wrox.com --> markup --> xslt, message
#46 of a set of 95.

Must I say that I enjoyed reading his book enormously!!! 

Here's Mike's reply to my suggestion that intersecting two node-sets
doesn't need an extension function:
----------------------------------- 

Date: Tue, 11 Jul 2000 09:25:14 +0100
 
Author: Kay Michael <Michael.Kay@icl.com>
 
Subject: Re: Q: An efficient way to test if a node belongs to a node
list
 
Body: > I believe this is not true! Here's how to output the 
> intersection of two node-sets, ...
>
> MHK: But saying things can't be done is dangerous, it wouldn't 
> surprise me to be proved wrong on this one.

I had a think about this in the bath. The following expression finds
the intersection of $ns1 and $ns2

$ns1[count(.|$ns2)=count($ns2)]

So I've proved myself wrong before anyone else got the chance to do
it first.

Mike Kay
 

-------------- Original message ----------------

Date: Wed, 2 Aug 2000 09:56:58 +0100 
From: Kay Michael <Michael.Kay@icl.com>
Subject: RE: How can I test if an node included in a nodeset

> I have a selected a nodeset in a variable($nodeset) and now I 
> would compare this nodeset to an node and I would detect if this node

> included in the nodeset.
> 
This is surprisingly difficult. Saxon and xt both provide 
intersection() as
an extension function. The only way of doing it within the standard is 
to
rely on union:

count($nodeset) = count($nodeset | $node)

will be true iff $node is a member of $nodeset.

Mike Kay


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