John McGowan wrote:

I'm specifically asking about "stylesheet functions"

Yes, I see now, sorry. I thought you meant xslt functions.

The only thing I can think about is something I saw in Michael Kay's ref book: you can use it (according to him) to test for a java method, like this:

use-when="function-available('Charset:isAvailable', 1)"

but not sure if this is of help with your user defined functions.

Cheers,
-- Abel