[xquery-talk] XQuery Feature: Grouping

[Jonathan Robie]

David Carlisle wrote:
>> Can you be more specific about what you think this grouping operator 
>> should do?
>>     
>
> The facilities offered in xsl:for-each-group would be a useful start.
> (or less concretely, anything that met the grouping requirements in
> section 4 of http://www.w3.org/TR/2001/WD-xslt20req-20010214)
>   

Obviously, we are aware of xsl:for-each-group - one of the advantages 
that comes from working so closely with the XSL Working Group ;->

And this is a useful set of use cases. I imagine any work on XQuery 
grouping should include most of these use cases. I do not yet have a 
good feeling for what other use cases people might have when they think 
of 'grouping'.

> One thing that would make grouping easier would be support for higher
> order functions, which would of course be useful in lots of other places
> as well.
>   

XQuery is rather unusual, most functional languages support higher order 
functions, and they are indeed useful. The usual XQuery approach is to 
allow expressions to be composed from other expressions, as in several 
of the solutions shown here:

http://lists.w3.org/Archives/Public/www-ql/2003JanMar/0046.html

But higher order functions would be another useful approach.

Jonathan

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