sgn(bits) = false ', true ∈ bits ⊦ bits = []
Used simplifier rules: sgn-zero: ⊦ ¬ true ∈ bits ∧ bits ≠ [] → sgn(bits) = false ';% ⊦ boolvar ' = boolvar0 ' ↔ boolvar ↔ boolvar0;