Re: [xsl] Beginning an XPath expression with a function call?

[Oleg Tkachenko <olegt@xxxxxxxxxxxxx>]

Monier, Yves wrote:

> Given an XPath expression (for example //foo/foo2) that works for a given
> xml, I would like to use the substring-before function, to keep only the
> characters in //foo/foo2 before '-'.
> The XPath would then become substring-before(//foo/foo2, '-')
>
> It seems that both XPath 1.0 specs, MSXML 4, Saxon 7.4 and XalanJ 2.5 refuse
> such construction (e.g. having a function call as root of an XPath
> expression). Note that it works with Xalan C++ 1.4. Should it, or not,
> regarding the specs?

It's perfectly valid XPath expression, but it cannot be used with / and 
// operators, because they explicitly require the expression to evaluate 
a nodeset:
"The / and // operators compose an expression and a relative location 
path. It is an error if the expression does not evaluate to a node-set."
http://www.w3.org/TR/xpath#node-sets
And of course it cannot be used with xsl:apply-templates or xsl:for-each 
or msxsl's selectNodes, because they all require nodeset as result of 
the expression's evaluation.

> Do you know if there is a simple "legal" XPath-only-based solution to
> achieve the same result?
You can use function call as first part of of the path expression, 
day-to-day example is document('foo.xml')/*//bar like expressions or 
$foo/bar expressions.
What are you trying to achieve actually? substring-before(//foo/foo2, 
'-') is ok, have you tried
<xsl:value-of select="substring-before(//foo/foo2, '-')"/>
--
Oleg Tkachenko
Multiconn Technologies, Israel


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