RE: [xsl] Using XSLT 1.0 , I have tried using the Meunchian methodsolutions on

[Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>]

At 06:57 PM 12/19/2006, you wrote:
> I thought he was already using nested loops?  The outer looped through
> the nodes selected by the key, then the inner iterated through all nodes
> selected by the key using the FilingType of the context node in the
> outer loop.  Since he wished to display AgencyName once in the inner
> loop, using position() should be appropriate there.  I could have
> misread the original post, of course.

No, Brian, in the context, you're correct. I was just cautioning that 
the same thing might not work in just any context.

position() is tricky and often the source of various mysterious bugs, 
because it usually works (as in this context), but then in another 
context it doesn't.

Specifically, when you say for-each select="key('a','string')"> the 
current node list includes the nodes returned by the key with the 
value 'b' in document order, and only those nodes, so it's safe to 
use position(). But if, for example, you say apply-templates and 
select some "invisible" text nodes, or if you say key('a',path) and 
there is more than one node in path, you may get more nodes than you 
expect, and position() may throw you off.

I mention this position() peskiness almost every time it comes up on 
the list, not because the solutions offered won't work (they usually 
will), but because they often run a risk of misleading the 
inexperienced, and hence of causing code to break when the "same" 
technique is used elsewhere. It's natural to think that position() 
refers to the position of a node in the source tree relative to 
others. But it doesn't. (And keep in mind that many people are 
learning XSLT by reading solutions to others' problems on the list.)

And because it's obscure, problems related to use of position() are 
almost impossible to debug if you're not already in the know.

Cheers,
Wendell



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Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
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