static <A> Pair<L<A>> filterAntiFilterByBitSet(L<A> list, byte[] bitSet) {
  int n = l(list), nSet = bitCount(bitSet);
  L<A> l1 = emptyList(nSet);
  L<A> l2 = emptyList(n-nSet);
  for i to n:
    (getBit(bitSet, i) ? l1 : l2).add(list.get(i));
  ret pair(l1, l2);
}