Re: [xsl] Transitive closure for XPath

Subject: Re: [xsl] Transitive closure for XPath
From: "Christian Nentwich" <c.nentwich@xxxxxxxxxxxx>
Date: Thu, 19 Apr 2001 22:09:39 +0100
> Cute. Presumably as well as
> closure(/closure/node[1], id(@child))
> you could have
> closure(/closure/node[1], key("myKey", @child))
> You need delayed evaluation of parameters. Is this straightforward in
> other XSLT engines?

That's the one thing that is a bit worrying, the repeated and delayed
evaluation of the same parameter. It was straightfoward enough in Xalan
(although I had to override the default method, which evaluates the
parameters before passing them to the function). I have not even attempted
to understand the implications of this for optimised queries.

I am not an expert in XPath details, so I wonder how feasible it would be to
disguise this as an axis: /*/node[1]/closure::id(./@child) ? A function is
definitely much easier to implement though.

> (Of course I'd like to rename it to expand-o-graph() since that's how I
> visualise its operation)

Yes, or bounded avalanche operator :)


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