| ⊦ # bits0 ≤ n ∧ ¬ bits0.first ∧ bits ≠ [] ∧ bits0 ≠ [] → sgn(bitsand(lastn(n, fillsgn(n, bits)), bits0)) = sgn(bitsand(bits, bits0)) |
# bits0 ≤ n ⊦ bits = [], bits0 = [], sgn(bitsand(lastn(n, fillsgn(n, bits)), bits0)) = sgn(bitsand(bits, bits0)), bits0.first