fn:document, fn:function-available: default arguments

[rhdunn]

This issue tracks the changes needed to the built-in functions to allow them to combine the declarations into a single definition with default parameter values.

The general approach to this is to make required arguments optional if they are for a function signature that is not the lowest argument count signature, and move any associated logic into the function.

fn:document

1. Change fn:document/$base-node from node() to node()?.

- If $base-node is supplied,
+ If $base-node is not empty,

fn:function-available

1. Change fn:function-available/$arity from xs:integer to xs:integer?.

If $arity is the empty sequence, the function-available function returns true if and only if there is at least one available function (with some arity) whose name matches the value of the $name argument.

If $arity is not the empty sequence, the function-available function returns true if and only if there is an available function whose name matches the value of the $function-name argument and whose arity matches the value of the $arity argument.

[ChristianGruen]

@rhdunn I can’t really judge (as it affects XSLT functions): Is this still valid?

[michaelhkay]

Good catch, yes, we've made this change across all the F+O functions but it still needs to be made to XSLT functions.

[ndw]

What's above are just examples, the problem is likely a little wider.