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Re: For expressions and / operator in XPath 2.0 (Was: Re: [x

Subject: Re: For expressions and / operator in XPath 2.0 (Was: Re: result = node1 * node2 and then get total of all the result from whole document at the end)
From: Jeni Tennison <jeni@xxxxxxxxxxxxxxxx>
Date: Wed, 2 Jan 2002 23:15:50 +0000
like operator in xpath
Hi Mike,

> It would mean, for example, that sum(XXX/@value) would not
> necessarily give the same answer as sum(XXX/(@value+0)) (where XXX
> is an arbitrary expression); though it would give the same answer
> 99% of the time, which would make the exceptions even more
> surprising.

Gah, I see. There's sort of the same kind of thing with:

  section[keyword = $keyword]

and

  section[starts-with(keyword, $keyword)]

and

  section/keyword[starts-with(., $keyword)]

which we have to answer questions about all the time.

> After months of agonising on this one, we just decided to keep
> things simple: "/" eliminates duplicates and returns results in
> canonical order, "for" retains duplicates and retains the ordering
> of the operand. I was sad to lose "sum(//rate/(@value * @quantity))"
> but I'd rather make it an error than have it return results that
> were difficult to explain to people.

It's a shame. I do dislike all the keywords that seem to have infected
XPath, which make it seem more like a programming language in its own
right than a simple expression language :( I don't suppose we could
get rid of this one and use some kind of symbol or operator instead,
like:

  //rate -> (@value * @quantity)

Cheers,

Jeni

---
Jeni Tennison
http://www.jenitennison.com/


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