Michael, Dimitri.

you are right it shouldn't be a dark corner, but it IS in practice. This 
does do people's heads in... and it's a source of bugs. I've been called 
on site by clients just to find and fix this particular problem quite a 
few times.

The usual story goes as follows: "ah well we used to use select="" but 
then we had to add some choose and if and had to use a child element". Boom.

Christian


Michael Kay wrote:
> This shouldn't be a dark corner, because the fact that nodes have identity
> is pretty fundamental, but sadly there are lots of people who aren't aware
> of the implications. The answer of course is (2).
> 
> Michael Kay
> http://www.saxonica.com/  
> 
> 
>>-----Original Message-----
>>From: Oleg A. Paraschenko [mailto:olpa@x...] 
>>Sent: 01 September 2005 20:45
>>To: xml-dev
>>Subject: [xml-dev] quiz on select vs copy-of
>>
>>  Hello,
>>
>>  do you know the dark corners of XSLT? Here is one. Compare two
>>variables:
>>
>><xsl:variable name="v1" select="some-xpath"/>
>><xsl:variable name="v2"><xsl:copy-of 
>>select="some-xpath"/></xsl:variable>
>>
>>  Are "v1" and "v2" the same? I mean: can "v1" and "v2" be used in a
>>program interchangeably? Answers:
>>
>>1) yes
>>2) no
>>3) implementation-dependant
>>
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>.
>>
>>  The right answer is (2): no. Changing a use of "v1" to 
>>"v2", or reverse,
>>might change the result of a stylesheet. I'll post an example 
>>later. Or
>>you can provide your version.
>>
>>
>>-- 
>>Oleg Paraschenko  olpa@ http://xmlhack.ru/  XML news in Russian
>>http://uucode.com/blog/  Generative Programming, XML, TeX, Scheme
>>
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> 
> 
> 
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