Re: [xsl] Filtering sequences of atomic types

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

At 2008-11-26 21:33 +0100, Christoph LANGE wrote:
> Dear all,
>
>   I'm trying to filter a sequence using a predicate that involves a node set.
> What I actually want to do is something like
>
> $string-sequence[. = //@xml:id]
>
> i.e. get all items of a sequence that occur as an xml:id attribute somewhere
> in the document.
>
> As that gives me the error message "XPTY0020: Cannot select a node here: the
> context item is an atomic value" (with Saxon 9.1), I tried
>
> $string-sequence[. = (for $n in (//@xml:id) return xs:string($n))]
>
> or even
>
> ('foo', 'bar')[. = (for $n in (//@name) return 'foo')]
>
> where the latter should actually return something like ('foo', 'foo', ...),
> and ('foo', 'bar')[. = ('foo', 'foo')] works, of course.
>
> My current workaround is translating the string sequence to a sequence of text
> nodes, but why doesn't it work with a sequence of atomic types?

Because there is no current node.

When you have "//@xml:id" that is saying in effect "from the root of 
the node tree of the current node find all xml:id attributes" ... 
since this is in a predicate on a sequence of strings, there is no 
node tree of the current node because the context item is a string not a node.

You probably want something like:

  <xsl:variable name="tree" select="/"/>
  <xsl:for-each select="$string-sequence[.=$tree//@xml:id]">
    ...

Or would this work even better for you:

  <xsl:for-each select="//@xml:id[.=$string-sequence]">
   ...

I hope this helps.

. . . . . . . Ken



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