| ⊦ bits = [], bits0 = [], bits2int(bitsor(bits, bits0) + bits1) = bits2int(bits0 + bits1), true ∈ bits |
⊦ ¬ true ∈ bits ∧ bits0.first ∧ bits ≠ [] ∧ bits0 ≠ [] → bitsor(bits, bits0) = bits0
¬(¬ true ∈ bits ∧ bits0.first ∧ bits ≠ [] ∧ bits0 ≠ []) ⊦ bits = [], bits0 = [], bits2int(bitsor(bits, bits0) + bits1) = bits2int(bits0 + bits1), true ∈ bits
Used terms: bits0, bits