JSONiq follows the W3C standard for constructing function items with named function references. The following explanations, provided as an informal summary for convenience, are non-normative.
If a function is builtin or declared in a prolog, in the same module or imported, then it is also possible to build a function item by referring to its name and arity.
Example 40. Named function reference
declare function local:sum($x as integer, $y as integer) as integer { $x + 2 }; local:sum#2
Result. (a function items)
Figure 26. NamedFunctionRef