Usage
plus.single.step(k, etatil, z, b, tau, m, v, t, eps=1e-15, e)
plus.check.eta(old.eta, new.eta, etatil, xi, z, v, eps=1e-15, e)
plus.hit.points(lam, lam.path)
plus.new.eta(eta, etatil, cross,p)
plus.not.in.loop( k, new.eta,e)
plus.penalty(m,a=0)
plus.recip(Q, eps=1e-15)
plus.knots(t=0,m=0)