static <A> L<A> sortedByComparator(Collection<A> l, Comparator<A> c) {
  L<A> l2 = cloneList(l);
  sort(l2, c);
  ret l2;
}

static <A> L<A> sortedByComparator(Comparator<A> c, Collection<A> l) {
  ret sortedByComparator(l, c);
}