Re: Designs for XSLT functions (Was: Re: RE: syntax su

> Interesting thread!
> 
> Here's another suggestion for the contentmodel of a hypothetical
> xsl:function:
> 
> <xsl:function name="my:func">
>   <xsl:param name="a"/>
>   <xsl:param name="b"/>
>    ...
>   <xsl:variable name="c" select="..."/>
>   <xsl:variable name="d" select="..."/>
>    ...
>   <xsl:return select="..."/>
> </xsl:function>
> 
> i.e
> 
> <!ELEMENT xsl:function (xsl:param*, xsl:variable*, xsl:return)>

This is pretty limiting.  I think the function body should have the content 
model of a template.

> The content model for xsl:return should be the same as for
> xsl:variable, allowing you to return arbitrary XPath values as well as RTFs.

Yup.

> The reason for allowing xsl:variable is an aid to split otherwise long XPath
> expressions that would appear inside the select of xsl:return and to allow 
> things like xsl:apply-templates and xsl:call-template to contribute to the
> result even when it's not an RTF.
> 
> I think there is a major gotcha when only allowing a single xsl:return:
> the lack of control structures in XPath. However, there is one in the
> XPath 2.0 Req: 2.2. I would prefere to shoehorn such a construct into
> XSLT 1.1 (!) rather than having a restricted mix (mess) of RTF and
> <xsl:return> just to get to the control structures. This opinion is
> strictly definition/implementation/optimization based. It's simply a
> cleaner solution in my opinion. I have no idea of what possible
> mess it would mean in terms of specifciation dependencies and
> versioning though ...

But if full template semantics are allowed, none of this is a problem.  
Remember my example

<exsl:function name="my:func">
  <xsl:choose>
   <xsl:when test="$i-want-my-rtf">
    <exsl:return>
     foo
    </exsl:return>
   </xsl:when>
   <xsl:otherwise>
    <exsl:return select="'foo'" />
   </xsl:otherwise>
  </xsl:choose>
</exsl:function>

> Another thing: wouldn't <xsl:result> be a better name for <xsl:return>
> (assuming it can only appear once)? At least to me it sounds more declarative.

Yes.  I think "exsl:result" is the more properly declarative name.

> About calling functions: I vote strongly for positional parameters, as
> said before: consistent with other XPath functions, and most other
> languages too.

What about the idea of both?  a positional static and a named dynamic 
invocation?

-- 
Uche Ogbuji                               Principal Consultant
uche.ogbuji@xxxxxxxxxxxxxxx               +1 303 583 9900 x 101
Fourthought, Inc.                         http://Fourthought.com 
4735 East Walnut St, Ste. C, Boulder, CO 80301-2537, USA
Software-engineering, knowledge-management, XML, CORBA, Linux, Python



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