Subject: Re: [xsl] Sequential numbers in pure xslt, breaking the no-side-effect rule From: David Carlisle <davidc@xxxxxxxxx> Date: Fri, 16 Mar 2007 15:55:08 GMT |
> I don't have that luxury, Sometimes (like here) it's tempting (or even from a performance point of view perhaps a requirement) to say you need an imperative assignment with side effects and guaranteed execution order, but in a strong sense that is not true. That's Turing's (standing on Church and Godel and others) main insight: Any machine (or programming language) that can compute anything intersting at all can compute exactly the same algorithms as every other one. So no algorithm _requires_ state to be mantained as a side effect, it's _always_ possible to rewrite the algorithm so that any state required is explictly passed from function to function. Now it may be that in practical cases the amount of state that would be required to be passed is large and you don't want to pass it through a function call interface, but well, that's the job of the optimising complier to sort out. Saying that the _end user_ has to rewrite the algorithm in an imperative style in order to get an effective computation is just so 1960's:-) David
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