if (b0 != null && b0.length() <= b.length()) {
assertEquals(a.cardinality(), b.cardinality());
BitSet a_and = (BitSet)a.clone(); a_and.and(a0);
BitSet a_or = (BitSet)a.clone(); a_or.or(a0);
BitSet a_xor = (BitSet)a.clone(); a_xor.xor(a0);
BitSet a_andn = (BitSet)a.clone(); a_andn.andNot(a0);
FixedBitSet b_and = b.clone(); assertEquals(b,b_and); b_and.and(b0);
FixedBitSet b_or = b.clone(); b_or.or(b0);
FixedBitSet b_xor = b.clone(); b_xor.xor(b0);