AW: [xsl] Variables

["Mengel Andre (FV/SLM) *" <Andre dot Mengel at de dot bosch dot com>]

Hi Jeni,

thanx for your detailed description.

Best regards,

André

> -----Ursprüngliche Nachricht-----
> Von: Jeni Tennison [mailto:mail@jenitennison.com]
> Gesendet: Donnerstag, 17. Mai 2001 15:43
> An: Mengel Andre (FV/SLM) *
> Cc: 'XSL-List@lists.mulberrytech.com'
> Betreff: Re: [xsl] Variables
> 
> 
> Hi Mengel,
> 
> > Could someone explain me the following example of the W3C 
> specification
> >
> > <xsl:variable name="n">2</xsl:variable>
> > ...
> > <xsl:value-of select="item[$n]"/>
> >
> > This will output the value of the first item element, because the
> > variable n will be bound to a result tree fragment, not a number.
> > (See chapter 11.2)
> >
> > What is the reason for outputing the value of only the first item
> > element ?
> 
> The definition of xsl:value-of indicates that it evaluates the
> expression in its select attribute, and converts that to a string in
> the same way as the string() function (see Section 7.6.1 of the XSLT
> Recommendation).
> 
> When you convert a node set to a string with the string function, you
> always get the value of the *first* node in that node set (see Section
> 4.2 of the XPath Recommendation).
> 
> The XPath 'item[$n]' gets a node set of item elements that are
> children of the current node. The item elements that are chosen depend
> on the data type of the predicate. If the predicate were a number
> (e.g. item[2]) then it would get the item element that had that
> position amongst its sibling item elements (i.e. the second item
> element).  Otherwise, the expression is converted to boolean in the
> same way as the boolean() function (see Section 2.4 of the XPath
> Recommendation).
> 
> In this case, and the point of the example, the variable $n is set to
> a result tree fragment. Evaluating the variable gives a result tree
> fragment, not a number, so it's converted to a boolean.  Converting
> a result tree fragment to a boolean always results in true() because a
> result tree fragment is treated, in this context, like a node set with
> a single root node (which has children as defined by the content of
> the variable).
> 
> As the predicate always evaluates to true, the node set returned by
> 'item[$n]' holds all the item children of the current node.  When this
> node set is evaluated as a string, then you get the string value of
> the first of the item elements.
> 
> I hope that helps,
> 
> Jeni
> 
> ---
> Jeni Tennison
> http://www.jenitennison.com/
> 
> 

 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list