| ∃ bits0. int2bits(i) = bits0 + lastn(m, int2bits(i)) ∧ # bits0 = # int2bits(i) - m, m ≤ # int2bits(i), 0 < i ⊦ m = 0, bits2int(lastn(m, int2bits(i))) = i % 2 ^ n→i(m), lastn(m, int2bits(i)).first |
# bits = # int2bits(i) - m, int2bits(i) = bits + lastn(m, int2bits(i)), 0 < i, m ≤ # int2bits(i) ⊦ bits2int(lastn(m, int2bits(i))) = i % 2 ^ n→i(m), m = 0, lastn(m, int2bits(i)).first