Re: [xsl] R: [xsl] IQuestion about XSLT and Math Operations

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

At 2005-12-05 13:09 +0100, drkm wrote:
> "G. Ken Holman" wrote:
> > At 2005-12-05 00:23 +0100, Villani Alessandro wrote:
>
> > ><?xml version="1.0" encoding="utf-8"?>
> > ><xsl:stylesheet
> > > xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
> > > version="1.0">
> > >      <xsl:output method="xml"
> > >        omit-xml-declaration="yes" indent="yes"/>
> > >      <xsl:template match="parameters">
> > >           <xsl:param name="r50">
> > >...
> > You can just do:
> >    <c2><xsl:value-of select="r3 * r2"/></c2>
>
>   That's not the same things (it's an xsl:param, not an xsl:variable).

Some of my students come to class confused about this.  Constructs 
defined by <xsl:param> and <xsl:variable> are used in *precisely* the 
same way once a value is bound.  The sole difference between the two 
is how the value is bound:  for a variable the value can only be the 
value declared, while for a parameter the value is the declared value 
only if it is not overridden when the template invoked with a 
<xsl:with-param>.  Otherwise they are treated as exactly the same 
kind of thing.

In the author's example, the parameter is declared as a parameter of 
an unnamed template rule, thus the *only* way that a value other than 
the default value is bound to the parameter is through 
<xsl:with-param> as a child of <xsl:apply-templates>.  Given that all 
of the information used is provided for in the source tree, I doubt 
that the template rule match was necessarily parameterized ... 
without more of the example code showing his use of 
<xsl:apply-templates> I made the assumption (and it was an 
assumption) that the author was using <xsl:param> unnecessarily and 
that <xsl:variable> was just as suitable.

Because as I said, except for how the value is bound, they are indeed 
the same thing when being used.  There are no differences in reference and use.

I hope this is considered helpful.

. . . . . . . . . Ken


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