Subject: Re: Regular expression functions (Was: Re: [xsl] comments on December F&O draft) From: David Carlisle <davidc@xxxxxxxxx> Date: Fri, 11 Jan 2002 15:10:42 GMT |
> Is it realistic to expect implementations to guarantee to return the > same thing for any given combination of arguments for a particular > function? Yes for built in xpath functions. they are all (so far) defined so that is true. Probably not for externally defined extension functions but the behaviour of any expression using such function really can't be specified in Xpath. For example currently given a variable definition and three references to it, a system is free to evaluate the variable once and use that value three times, or just to re-evaluate the expression each time, or something in between. Mike's given examples on ths list before now of the heuristics saxon uses to decide which to do. If a variable definition uses a function that isn't guaranteed to return the same result if called with the same arguments then it is legal for a reference, $x, to that variable to produce different answers if it appears twice in the same scope. this is something you really want to avoid.... David _____________________________________________________________________ This message has been checked for all known viruses by Star Internet delivered through the MessageLabs Virus Scanning Service. For further information visit http://www.star.net.uk/stats.asp or alternatively call Star Internet for details on the Virus Scanning Service. XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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