Add dynamic function calls, inline functions, function literals...

[JohannesLichtenberger]

For instance:

xquery version "3.0";
declare namespace db="http://sirix.io/xquery/db";
declare function db:map($func, $list) {
    for $item in $list return $func($item)
};
let $fun := function($x) { $x * $x }
return db:map($fun, 1 to 5)

[JohannesLichtenberger]

So far I've added closures and anonymous functions.