Barnes-Hut Tree Code Submitted to PlaneT

I've just submitted some new code to PlaneT which implements Barnes-Hut Trees in PLT Scheme. It's surprisingly (to me) fast, creating a 100K-body tree in about 30 seconds on my old PowerBook G4 800 Mhz.

This is just another step in my code clean-up in preparation for comparing our algorithm to the standard leapfrog algorithm of cosmological codes.