Tuple types

[John Snelson]

Hi Pavel,

Tuple types won't make it into XQuery 1.1, but the closures support in 
higher order functions allows you to effectively return sequences of 
sequences:

(: Wrap a sequence as a function item :)
declare function local:ref($arg as item()*) as function() as item()*
{
     function() { $arg }
};

(: Unwrap a sequence from a function item :)
declare function local:deref($arg as function() as item()*) as item()*
{
     $arg()
};

John

Pavel Minaev wrote:
> I can't find the link now, but I recall seeing some mentions of a
> possibility of introducing some form of tuple type (in a sense of an
> aggregate of arbitrary-typed values - including sequences) in XQuery
> 1.1, specifically to tackle the multiple-return-values and
> sequences-of-sequences problems. Are there any recent developments on
> the subject? I don't see anything like this in the most recent draft,
> but then higher-order functions aren't there either, and yet, judging
> by their presence in Saxon 9.2, they are well-shaped by now.
> 
> If this isn't going to make it into 1.1, are there any other new
> features that I might have missed that would make it possible, for
> example, for a function to return two sequences?
> _______________________________________________
> http://x-query.com/mailman/listinfo/talk
> http://x-query.com/mailman/listinfo/talk


-- 
John Snelson, Oracle Corporation            http://snelson.org.uk/john
Berkeley DB XML:            http://oracle.com/database/berkeley-db/xml
XQilla:                                  http://xqilla.sourceforge.net