old1 := altBit(z1, i)
		if old != old1 {
			t.Errorf("bitset: inconsistent value for Bit(%s, %d), got %v want %v", z1, i, old, old1)
		}
		z := new(Int).SetBit(z, i, 1)
		z1 := altSetBit(new(Int), z1, i, 1)
		if z.Bit(i) == 0 {
			t.Errorf("bitset: bit %d of %s got 0 want 1", i, x)
		}
		if z.Cmp(z1) != 0 {
			t.Errorf("bitset: inconsistent value after SetBit 1, got %s want %s", z, z1)
		}

        }
        return false;
      }

      @Override
      public Iterator<Set<E>> iterator() {
        return new AbstractIterator<Set<E>>() {
          final BitSet bits = new BitSet(index.size());

          @Override
          @CheckForNull
          protected Set<E> computeNext() {
            if (bits.isEmpty()) {
              bits.set(0, size);
            } else {