l.elem(i) = pokeSpin(l.elem(i),r.elem(i),row);
pokeSpin(l.elem(i),r.elem(i),row);
pokeSpin(PVector<T1,N,C>& l, const PVector<T2,N,C>& r, int row){  for(int i=0; i < N; ++i)    l.elem(i) = pokeSpin(l.elem(i),r.elem(i),row);  return l;}