proposition: Lemma testbit_false : forall a n, 0<=n -> (a.[n] = false <-> (a / 2^n) mod 2 == 0).
proof: Proof. intros a n Hn. rewrite <- testbit_spec' by trivial. destruct a.[n]; split; simpl; now try order'. Qed.
imports: Bool ZAxioms ZMulOrder ZPow ZDivFloor ZSgnAbs ZParity NZLog