Re: [xsl] Re: Re: Assignment no, dynamic scoping si (was: Wishes for XSL revisions ...

[Gunther Schadow <gunther at aurora dot regenstrief dot org>]

This is interesting, and darn close to what I was looking for,
indeed. You are a genious, Dimitre, even if hardly anyone
on this list may be. Where do you keep an archive on your other
generic template work which you seem famous for?

-Gunther

Dimitre Novatchev wrote:

> Gunther,
> 
> Recently I gave an example of dynamic creation of new functions. It described a
> "store" of variables and their values for a calculator. Maybe this could be helpful?
> 
> http://aspn.activestate.com/ASPN/Mail/Message/xsl-list/920880
> 
> Cheers,
> Dimitre Novatchev.
> 
> 
> 
> Gunther Schadow <gunther at aurora dot regenstrief dot org> wrote:
> 
> 
> Mike Haarman wrote:
> 
> 
> 
>>>There is even a simpler approach using only XSLT: I can make all
>>>templates use an argument that is a constructed node-set
>>>containing name-value pairs (the dynamic environment) and references
>>>to the bindings in this environment would be supported by some
>>>xpath selects in that environment node-set.
>>>
>>>
>>>
>>Thanks for the insight.  Can the dynamic environment be incorporated into
>>the internal subset via parameter entities?  Such a solution does not
>>leave interoperability entirely in crutches.
>>
> 
> 
> This is what it would take:
> 
> all template calls or applies that typically just look like
> this:
> 
> <xsl:apply-templates select='...'/>
> 
> <xsl:call-template name='...'/>
> 
> would have to be transformed into:
> 
> <xsl:apply-templates select='...'>
>    <xsl:with-param name='environment' select='$environment'/>
> </xsl:apply-templates>
> 
> <xsl:call-template name='...'>
>    <xsl:with-param name='environment' select='$environment'/>
> </xsl:call-template>
> 
> and every template
> 
> <xsl:template ...>
>    ...
> </xsl:template>
> 
> transformed into
> 
> <xsl:template ...>
>    <xsl:param name='environment' select='/..'>
>    ...
> </xsl:template>
> 
> The environment would be a node set like this:
> 
> <foo>bar</foo>
> <nick>nack</nick>
> <mynodes><bee><bop/></bee></mynodes>
> <nick>before nack</nick>
> 
> with each name being an element and the value bound to the name
> a node-set content of the element.
> 
> Adding a binding foo='bar' to the environment would be
> 
> ...
> <xsl:variable name='new-environment-rtf'>
>     <xsl:element name='foo'>
>       bar
>       <xsl:copy-of select='$environment'/>
>     </xsl:element>
> </xsl:variable>
> ...
> <xsl:apply-templates select='...'>
>    <xsl:with-param name='environment'
>                    select='msxsl:node-set($new-environment-rtf)'/>
> </xsl:apply-templates>
> ...
> 
> Then querying the environment for the binding foo would be:
> 
> 
> <xsl:value-of|copy-of|...
>       select='$environment/foo[1]'/>
> 
> This always picks the first element. This is what does the
> shadowing of the old bindings by the new bindings. That's not
> strictly necessary, because the old bindings wouldn't have
> to be carried along as long as you don't have functional
> arguments that depend on old bindings (which I don't see a
> way of having in XSLT anyway.) But there is no easy way of
> replacing the old bindings that are to be shadowed without
> more work, so we can just carry them along.
> 
> May be it would be easier to carry the bindings as elements
> such as <binding name='foo'>bar</binding> (could be easier
> to use with keys or something.) But the principle is the same.
> 
> In any event, I don't quite see how parameter entities would
> make that much easier. What one would need is macros (ugh)
> or just simply an XSLT doing the transforms described above.
> In any event, it's a lot of burden to do for routine use
> just in case someone wants to have a few dynamically scoped
> variables.
> 
> 
> 
> 
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-- 
Gunther Schadow, M.D., Ph.D.                    gschadow@regenstrief.org
Medical Information Scientist      Regenstrief Institute for Health Care
Adjunct Assistant Professor        Indiana University School of Medicine
tel:1(317)630-7960                         http://aurora.regenstrief.org



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