Question / Suggestion : Template mechanisms and operator overloading for XQUERY 3.++ ?

On Sun, Jan 4, 2015 at 11:05 AM, jean-marc Mercier <jeanmarc.mercier at gmail.com> wrote: > Hello, > > I was wondering if it is possible to improve template programming and > operator overloading with XQUERY 3.? > > 1) template programming : XQUERY provides a quite natural template mechanism > using type switch and instance: > > declare function yell($animal) { > if ($animal instance of element()) then > > return typeswitch($animal) > case element(cow) return "Moo" > default return "..." > > else "this is not an animal" > }; > > However, I wonder whether it could be possible to provide such a mechanism > directly at the interpreter level ? For instance, the following code seems > coherent and concise : > > declare function yell($animal as element(cow) ) {"Moo"} > declare function yell($animal as element() ) {".."} > declare function yell($animal ) {"This is not an animal"} > > As far as I understand, XQUERY functions identification seems to be achieve > through a couple (name, arity). Would it be difficult to extend it with > (name,signature or predicate) ? > > 2) Operator overloading (quite linked to the previous question) > > I don't know how to overload operators with XQUERY. For instance I would > like to define something like > > declare function > array:operator+($left,$right){array:for-each-pair($left,$right,function($a + > $b) { $a + $b } )} > > Is it possible ? > > I know that I can survive writing > > declare function > array:plus($left,$right){array:for-each-pair($left,$right,function($a + $b) > { $a + $b } )} > > but when one start to write algorithmic code, it is far easier and > understandable to write $a+$b than array:plus($a,$b) > > > >