[math-fun] multi-D hilbert curve

3D (e.g.) Hilbert is easy with the finite state machine. Three bits of t in, one bit of x, y, and z out, plus state change. --rwg

--well... actually figure out the state machine for arbitrary D, and do it in a way that we do not need no stinking huge 2^D entry table to store the state-rules, and then I'm sold. There's some disgusting computer programs out there I found with google to do multi-D hilbert curves, but there really ought to be a nice way that takes under 1 page of code. And they haven't found it.