proposition: Lemma shiftl_spec_high : forall a n m, 0<=m -> n<=m -> testbit (shiftl a n) m = testbit a (m-n).
proof: Proof. intros a n m. zify. intros Hn H. rewrite Z.max_r by auto with zarith. now apply Z.shiftl_spec_high. Qed.
imports: ZArith OrdersFacts Nnat NAxioms NSig Lia