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RE: [xsl] Hierarchy problem


Subject: RE: [xsl] Hierarchy problem
From: DPawson@xxxxxxxxxxx
Date: Mon, 22 Jul 2002 15:38:16 +0100

David C wrote:

> you are a member of the set of all men 
> (item being a member of a set)
> the set consisting of you is a subset of the set of all men
> (singleton set being a subset of a set)

And the empty set is also a valid subset of any set?
> 
> In some sense these have the same meaning but 
> 
> > Also, if $y is a node which doesn't exist (or is higher in 
> the doc tree than
> > $x) surely the statement would come back true?
> 
> higher up the node tree it would be false.

I guess this is coming down to the example you posted?
I *could* create a nodeset such as 

value-of select="* |//node[2]"/>
which could be of that form?
Just that we were talking about descendant and child axis
selectors, hence your comment?


 empty set it wuld be true
> which is part of the difference between "subset" and member of.
empty set is a subset of, but not a member of, set X.
(ignoring difference between {x} and x)


> if y is the empty set and x is a set then y is a subset of x.
Thanks, that clarifies.


> if you want to check that it is a proper subset (ie not empty and not
> the whole thing) you need to test for that as well, so 
> 
> test="$y and count($x/*|$y) = count($x/*)"

This (for the variables we defined), tests that y exists and is none empty.


> 
> or if you don't want the sets y and x to be equal
> 
> 
> 
> test="$y and count($x/*|$y) = count($x/*) and 
> not(count($x)=count($y))"

My head hurts, I'll think on that one :-)

Thanks David.

Regards DaveP

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