>> I have occasionally wondered whether the ban on using tunnel
>> parameters inside a function is perhaps rather paternalistic.
>
> I think so - you can presumably have a template  wrapper whose only
> purpose  is to return a tunel parameter, and call it from within the
> function.
>

No, you can't: if template T1 calls function F and F calls template T2, T2
gets an empty set of tunnel parameters.

Michael Kay
Saxonica