static <A> L<A> subListOfCollection(Collection<A> c, int from, int to) {
  int n = l(c);
  to = min(to, n);
  if (from >= n || to <= from) ret ll();
  L<A> l = new L(to-from);
  Iterator<A> it = iterator(c);
  repeat from { it.next(); }
  while (from++ < to) l.add(it.next());
  ret l;
}