Subject: Re: [xsl] The evaluate function From: Trevor Nash <tcn@xxxxxxxxxxxxx> Date: Thu, 03 Jan 2002 18:47:38 +0000 |
Hi Jeni, On Thu, 3 Jan 2002 15:32:47 +0000, you wrote: >Just to check that I'm following you correctly. You're saying that >because the string passed to the evaluate() function could contain >anything, the processor can't know whether it contains a reference to >the $x variable in which the $x variable is treated as a node set, and >therefore cannot optimise the storage of the $x variable. > Yes, thats it. >In other words, the processor no longer has the opportunity to scan >for uses of $x to work out what kind of value it is. > >I can see that's a problem. But couldn't the user could help the >processor here by making the type of $x (and other global variables) >explicit: > ><xsl:variable name="x" type="xs:string"> Bear in mind its an example of a class of problems, offered in support of Mike's comment about trying to obtain as much information as possible statically. Individually all these problems are soluble, of course - but you have to think about how complex you make the language. >The possible performance hit is, in my opinion, not enough of a reason >to omit a facility that makes the impossible possible. > Nothing is impossible ;-) I also care about reliability. If the compiler doesn't see half the source code, it will also miss half the errors. Some of which we'll see on this list ;-(( I do worry that 'eval' could create more problems than it solves. To quote another message today: > <xsl:value-of select="concat('/result/row[1]/column[', position(),']/@name')"/> Could be the next disable-output-escaping! Regards, Trevor -- Traditional training & distance learning, Consultancy by email Melvaig Software Engineering Limited voice: +44 (0) 1445 771 271 email: tcn@xxxxxxxxxxxxx XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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