Re: [xsl] XSLT: XPath: Siblings

Subject: Re: [xsl] XSLT: XPath: Siblings
From: Francis Norton <francis@xxxxxxxxxxx>
Date: Wed, 28 Feb 2001 10:34:54 +0000

Lee Goddard wrote:
> My understanding of this has to be wrong:
It is :)

> <xsl:apply-templates/>
> <xsl:template match="/*/*">
>          | <xsl:value-of select="name()"/>
>          ---
>          <xsl:value-of select="preceding-sibling::*[name()]"/> |
> </xsl:template>
> Shouldn't the second clause above output the value
> of the name of the preceding sibling?  It seems to be
> outputting the text content of the first element on
> the page.  I can't understand why?
Because the stuff inside the square bracket is a predicate, like an SQL
where clause. That's why you're getting content rather than name. 

The reason you're getting the first one is, I suspect, that although the
preceding-sibling axis is ordered <em>as far as predicates on it are
concerned</em>. Once you've applied an accidental predicate which
selects every element on the axis (because every element has a name,
which got converted to a boolean true) the result of the expression is a
good old-fashioned un-ordered node-set. xsl:value-of converts its select
argument to a string as if by string(), and the XPath spec says: 

"The string function converts an object to a string as follows:

              A node-set is converted to a string by returning the
string-value of the node in the node-set that is first in document
order. If the node-set is empty, an empty string is returned."

In other words, you want something like 

	<xsl:value-of select="name(preceding-sibling::*[1])"/>

> All I ever do is ask questions here... many thanks for
> all the help I get; I can repay you on the Perl lists
> at
No problem :)


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