Re: [xsl] XPATH | union operator question

["G. Ken Holman" <gkholman@xxxxxxxxxxxxxxxxxxxx>]

At 2003-12-19 16:05 +0100, christof.hoeke@xxxxxxx wrote:
> ###TODO
> in the following xml: if the inner @color is there use it, otherwise use 
> the outer @color

Use:   ( @color | ../@color )[last()]

> ###XML
> <test>
>         <line color="outer1">
>                 <x color="inner1"/>
>         </line>
> </test>
> ...
>         <xsl:template match="x">
>                         <xsl:value-of select="@color | 
> parent::line/@color"/><br/>
>                         <xsl:value-of select="parent::line/@color | 
> @color "/><br/>
>                         <xsl:value-of select="(@color | 
> parent::line/@color)[1]"/><br/>
>                         <xsl:value-of select="(parent::line/@color | 
> @color)[1] "/><br/>

In all four of the above, you are asking for the first in document 
order.  XPath returns the nodes unordered but XSLT examines the returned 
nodes in document order.  Since the <line> element is before the <x> 
element in document order, all four expressions are obtaining the colour 
attribute of <line>.

> what does the | operator in "@color | parent::line/@color" select? only 
> the most specific?

No, it only specifies the union of the two sets, with no duplicates.  XSLT 
will then consider the resulting set always in document order.

In my suggestion at top, the last() predicate will select the last of the 
set, which if there is only one is the one itself, but if there are two it 
takes the inner one.

I hope this helps.

............... Ken


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