Re: [xsl] Stange behavior with parameters, can somebody explain?

[Gunther Schadow <gunther at aurora dot regenstrief dot org>]

Oops, first the message was rejected and now it went through
twice. Sorry for that.

Thanks so much for the hint. Heck, I was fiddling with the
default rule for 'node()' but forgot about the root node.
This turns out to be a mistake similarly easy to make and
obscure to discover as the famous if(a = 0) fallacy in C.

Last night I rewrote all my parameter passing to use a
synthesized node structure only to loose sleep over it
and now turn it all back. Ah well. But I'm happy it was
my mistake.

Still, XSLT is great, I love it more each day.

-Gunther


Gunther Schadow wrote:

> Help! I'm ripping my heair out on this one. Please explain
> why the effect of with-param in apply-templates select='expr'
> depends on whether expr is an xpath selector on the current
> document or a synthesized node-set.
> 
> This is my XML file:
> 
> <ROOT><FOO/><BAR/></ROOT>
> 
> And this is the common part of an XSLT:
> 
> <xsl:stylesheet
>   version="1.0"
>   xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
>   xmlns:exsl="http://exslt.org/common";
>   exclude-result-prefixes="exsl">
> <!-- For MSXSL use this instead
>   xmlns:exsl="urn:schemas-microsoft-com:xslt"
> -->
> 
> <xsl:output method='xml' encoding="iso-8859-1" indent='yes'/>
> 
> <xsl:template match="ROOT">
>   <xsl:copy>
>     <xsl:apply-templates select='child::node()[1]'/>
>   </xsl:copy>
> </xsl:template>
> 
> <xsl:template match="BAR">
>   <xsl:param name='P'/>
>   <BAR P='{$P}'/>
> </xsl:template>
> 
> <!-- variant here -->
> 
> </xsl:stylesheet>
> 
> 
> Now I show you two variants of templates to deal with the FOO
> element. The first one uses the xpath selector:
> 
> <xsl:template match="FOO">
>   <FOO/>
>   <xsl:apply-templates select='following-sibling::node()[1]'>
>     <xsl:with-param name='P' select="'V'"/>
>   </xsl:apply-templates>
> </xsl:template>
> 
> when I run the transform, the result is:
> 
> <?xml version="1.0" encoding="iso-8859-1"?>
> <ROOT>
>    <FOO/>
>    <BAR P="V"/>
> </ROOT>
> 
> as it should be. However, when I use this variant:
> 
> <xsl:template match="FOO">
>   <FOO/>
>   <xsl:variable name='SYNTH'>
>     <BAR/>
>   </xsl:variable>
>   <xsl:apply-templates select='exsl:node-set($SYNTH)'>
>     <xsl:with-param name='P' select="'V'"/>
>   </xsl:apply-templates>
> </xsl:template>
> 
> the result is
> 
> <?xml version="1.0" encoding="iso-8859-1"?>
> <ROOT>
>    <FOO/>
>    <BAR P=""/>
> </ROOT>
> 
> as you see, here the parameter P <= V was not carried into the
> applied templates. Why is that?
> 
> I tried with both saxon and msxml and they both do the same
> thing.
> 
> Whatever it is, it is very obscure and makes my life very
> difficult.
> 
> Of course you don't see the use case from this dummed down
> example. My use case is string parsing for 'up-translation'
> where I match a head of a string then clip off the head
> and apply the templates on the rest of the text node. I
> cannot pass any parameters through this kind of process,
> ouch!
> 
> regards
> -Gunther
> 
> 
> PS: workaround seems to be to wrap the rest of the
> text node in an element with parameters as attributes
> or something. Argh!
> 


-- 
Gunther Schadow, M.D., Ph.D.                    gschadow@regenstrief.org
Medical Information Scientist      Regenstrief Institute for Health Care
Adjunct Assistant Professor        Indiana University School of Medicine
tel:1(317)630-7960                         http://aurora.regenstrief.org



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