Re: Variables

> 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 ?

You are referring to http://www.w3.org/TR/xslt#variable-values

Ok, step by step:
item[$n] contains a predicate: [$n], whose expression is $n, which
in turn is a result tree fragment.

Looking at http://www.w3.org/TR/xpath#predicates
you'll find the following:
"... If the result [of evaluating the PredicateExpr (my annotation)] is a
number, the result will be converted to true if the number is equal to the 
context position and will be converted to false otherwise; if the result is 
not a number, then the result will be converted as if by a call to the 
boolean function."

$n isn't a number (it's a rtf), so it is converted to a boolean, i.e.
to true (the rtf isn't empty).

item[true()] then selects all the item nodes, it is a node-set.

xsl:value-of select="item[$n]" outputs the string value of the
select expression: http://www.w3.org/TR/xslt#value-of
It does this by using the string function.

The string function with a node-set as argument returns the string value
of the first node in document order: http://www.w3.org/TR/xpath#function-string

In the end what you get is the value of first item element.

Questions?

I think in addition the work-arounds given in the XSLT spec, it's also
possible to write: item[number($n)]

Cheers,
Oliver


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|  ob|do        Dipl.Inf. Oliver Becker                             |
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