Keyword arguments

Where a function declaration requires or permits the last argument to be a map, the entries in the map may be supplied as keyword arguments. For example as an alternative to writing serialize($x, map{"method":"xml", "indent":true()}), you can now write:

serialize($x, method:="xml", indent:=true())

Positional arguments must always precede keyword arguments.

Although the feature is most obviously useful for functions like serialize where the final argument is a map following the "option parameter conventions", it can be used anywhere that it's appropriate to supply a map with string-valued keys as the last argument of a function call (including calls to user-defined functions).