The FP bit was fine. It's wrapping the functional program in the most obtuse syntax known to man (apart from C++ template syntax which at least has the get-out clause that it was never meant to be a turing complete programming language that programmers took seriously and used to get real work done) that's the problem.

Full disclosure: My last exposure to XSLT was a long, long time ago and I've been carefully avoiding it ever since.