On 5/10/2009 6:00 PM, Michael Kay wrote:
No, you can't do this.
(I can't think of any language where you can, except
some languages where variables are nothing more than macros, e.g. some OS
script languages).
(At the risk of going off-topic... Can't you do this with 'eval', e.g.
in Lisp or Perl?)
Regarding XSLT, wouldn't the 'evaluate' extension function EXSLT work?
(http://www.exslt.org/dyn/functions/evaluate/dyn.evaluate.html,
http://xml.apache.org/xalan-c/extensionslib.html#evaluate,
http://saxon.sourceforge.net/saxon7.9/extensions.html#evaluate)
The spec http://www.exslt.org/dyn/functions/evaluate/dyn.evaluate.html
says you can do just what the OP asked, it seems to me:
The dyn:evaluate function evaluates a string as an XPath expression and
returns the resulting value, which might be a boolean, number, string, node
set, result tree fragment or external object. The sole argument is the string
to be evaluated.
The string is always evaluated exactly as if it had been literally included
in place of the call to the dyn:evaluate function. For example:
<xsl:value-of select="dyn:evaluate('my:extension(. * $variable)')" />
Creates a text node with exactly the same value as:
<xsl:value-of select="my:extension(. * $variable)" />
Of course you lose some portability, but...
And now I see that Saxon supports this too:
http://saxon.sourceforge.net/saxon7.9/extensions.html#evaluate
The supplied string must contain an XPath expression. The result of the
function is the result of evaluating the XPath expression. This is useful
where an expression needs to be constructed at run-time or passed to the
stylesheet as a parameter, for example where the sort key is determined
dynamically.
The function saxon:evaluate(string) is shorthand for
saxon:eval(saxon:expression(string)). For the rules governing what may and
may not appear in the expression, see saxon:expression. The expression may
contain references to variables $p1, $p2, etc
So I'm really confused why Michael Kay would be saying that this isn't
possible in XSLT. Maybe he just means standard, portable XSLT?
Lars
--~------------------------------------------------------------------
XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
To unsubscribe, go to: http://lists.mulberrytech.com/xsl-list/
or e-mail: <mailto:xsl-list-unsubscribe(_at_)lists(_dot_)mulberrytech(_dot_)com>
--~--