Clusters are generalised constraints on sets of points in R^n. Cluster
types are Rigids, Hedgehogs and Balloons.
- binomial(n, k)
- over_angles(c1, c2)
- over_angles_bb(b1, b2)
- over_angles_bh(balloon, hog)
- over_angles_cb(cluster, balloon)
- over_angles_ch(cluster, hog)
- over_angles_hh(hog1, hog2)
- over_constraints(c1, c2)
- returns the over-constraints (duplicate distances and angles) for
a pair of clusters (rigid, angle or scalable).
- over_distances(c1, c2)
- determine set of distances in c1 and c2