void toggle(BitSet A, BitSet B) {
		for (int i = viewer.getAtomCount(); --i >= 0;) {
			if (!B.get(i))
				continue;
			if (A.get(i)) { // both set --> clear A
				A.clear(i);
			}
			else {
				A.or(B); // A is not set --> return all on
				return;
			}
		}
	}