As Rob points out, the simplest solution for simple cases is to use reverse().
That doesn't work if you want a composite sort key - sort by ascending country
then descending city. (Yes, an unconvincing use case, and frankly it's because
of the difficulty of finding a convincing use case that we didn't include this
capability).
If you know that the result of collation-key() will be xs:base64Binary then you
can do it, I suspect, by
fn:sort($places, function($p) { $p!country, $p!city => collation-key() =>
bin:not() } )
where bin:not is from http://expath.org/spec/binary#not
Michael Kay
Saxonica
> On 3 Dec 2015, at 12:44, Rob Stapper <[email protected]> wrote:
>
> Hi Christian,
>
> I suppose it can't be this simple: reverse( sort( ('A', 'AA', 'B')))
>
> Rob Stapper
>
> -----Oorspronkelijk bericht-----
> Van: [email protected] [mailto:[email protected]] Namens
> Christian Grün
> Verzonden: donderdag 3 december 2015 12:49
> Aan: [email protected]
> Onderwerp: [xquery-talk] fn:sort: sort for strings in descending order
>
> Hi everyone,
>
> As you may know, XQuery 3.1 introduces an interesting new fn:sort function,
> which can be used as alternative for the order by clause in FLWOR expressions
> [1]. It can e.g. be used to sort numbers in a descending order:
>
> sort(
> 1 to 10,
> function($k) { -$k }
> )
>
> I would be interested if anyone has already tried to get the descending order
> working for strings?
>
> sort(
> ('A', 'AA', 'B'),
> function($k) { ... }
> )
>
> I assume that string-to-codepoints could be used, and all Unicode points
> could then be negated, and additionally longer Unicode sequences would need
> to be preferred over shorter ones… But maybe there is a more concise solution?
>
> Thanks in advance,
> Christian
>
> [1] http://www.w3.org/TR/xpath-functions-31/#func-sort
>
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