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Re: Re: Re: A question about the expressive power and

Subject: Re: Re: Re: A question about the expressive power and limitations of XPath 2.0
From: David Carlisle <davidc@xxxxxxxxx>
Date: Sun, 13 Jan 2002 15:30:46 GMT
Re:  Re: Re: A question about the expressive power and
> A general statement about what "for" cannot do: Any problem of sequence processing,
> which requires that the result of processing an item be used as input for processing
> the next item(s).
> 
> Is this true?

yes I think so (ie you can't implement fold given map, more or less:-)

Of course you can generate a sequence of running totals using something
like 
for $i in 1 to  count($x)
return
sum($x[position() &lt;= $i])

but that's not really a "running total" as the first bits are repeatedly
re-avaluated, whereas what you'd like to do is pass a two argument
function over the list where at each stage the first argumant is the
previous result and teh second argument is the new item.

David

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