Re: Keyword arguments [was fn:slice]

> On 5 Dec 2020, at 21:01, Dimitre Novatchev <dnovatchev@gmail.com> wrote:
> 
> What about something as simple as this:
> 
> myFunction($arg1 as item()*, $arg2 as xs:integer default: 15, $arg3 as xs:string default: "Hi")

On the declaration side, this is very similar to what I've been proposing for XSLT - see https://qt4cg.org/branch/master/xslt-40/Overview-diff.html#xsl-function-name

The difference is that I proposed this would actually declare three functions myFunction#1, myFunction#2, and myFunction#3, because it can be called with 1, 2, or 3 arguments, and because its existence rules out the existence of any other function with this name and arity 2, 3, or 4. And I was thinking it purely as a better way of declaring a family of functions, not as something linked to changes in function call syntax.

> 
> "You can also use named arguments instead of positional arguments when invoking a method. When using named arguments, you specify the parameter name followed by a colon (":") and the argument. Arguments to the method can appear in any order, as long as all required arguments are present. "
> 

The main challenge is defining rules for unambiguously binding a function call to a declared function when there are several declared functions with the same name. This needs to handle both binding of static function calls and dynamic references.

Another detail, particularly for XSLT, is defining the rules for overriding of functions in other packages.

Michael Kay
Saxonica