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