Returning the name of a function as a string?

While porting and revamping my set (uniqueness) functions to Mathcad Prime 10 from Mathcad 15, I felt the need for speed.  Whilst I have set functions that will handle functions (to some degree), I wanted to use a uniqueness algorithm that relied on presorting an array.    However, Mathcad's built-in sort function won't sort functions.  After having a slight think about the problem, I wondered if I could use the format string function.  I can, sort of, in some cases, but not in general.

Apart from possibly digging around in the worksheet API, does anybody know of a more reliable method of converting a function name to its equivalent string or how to sort on functions?

Stuart