static <A, B extends A> L<A> listMinusSet(Collection<A> l, Collection<B> stuff) {
  if (empty(stuff)) ret asList(l);
  Set<B> set = asSet(stuff);
  new L<A> l2;
  for (A a : l) if (!set.contains(a)) l2.add(a);
  ret l2;
}