RE: object-oriented XSL

On Fri, 23 Aug 2002, Hunsberger, Peter wrote:

> There are times I wish that XSLT did have a better OO model, but that is in
> the way that includes and imports work.  XSLT 2 with the ability to have
> multi-modal templates may solve some more of this requirement.  However,
> there are still some gaps.  I'm still at a loss as to what your hoping to
> achieve beyond what existing languages can do?

what if defining a new XPath function was as easy as writing a named
template:

<xsl:function name="fib">
 <!-- calculates fibonacci numbers recursively -->
 <xsl:param name ="n" />
 <xsl:choose>
   <xsl:when test ="$n &lt;= 2" >
     <xsl:value-of select="1" />
   </xsl:when>
   <xsl:otherwise>
     <xsl:value-of select="fib($n - 1) + fib($n - 2)"/>
   </xsl:otherwise>
 </xsl:choose>
</xsl:function>

and what if you could define types and associate functions with them,
wouldn't that be pretty cool? XPath would have to be extended to allow
type function invokation, eg:

<xsl:type name="User">
  <xsl:variable name="name"/>

  <xsl:function name="User">
    <!-- this is a constructor, it is defined as a global XPath function and returns a User object -->
    <xsl:param name="name"/>
  </xsl:function>

  <xsl:function name="speak">
    <!-- this is a type function, can only be invoked on an object of type User -->
    <xsl:value-of select="concat('Hello, my name is ',$name)"/>
  </xsl:function>
</xsl:type>

<xsl:variable name="newUser" select="User('Fred')"/>
<xsl:value-of select="$newUser.speak()"/> <!-- uses '.' for type function invokation -->

quickly this takes us far from what XSLT is and what it does, but it's
exactly the sort of language possibilities that i would like to explore
further. for the oo to work well it would have to be procedural, not
functional or declarative, and allow simple things like variable
reassigning and side-effects.
add to this non-XSLT dynamically typed language a bit of function
overloading, (multiple?) inheritance, polymorphism and module building
constructs and i think that you really got something to kick .NET and C#
back down the hole they came from. want to write XML web services? write
them in XML! (then transform the result using XSLT!!)


/m (can't help but get political at times)


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