proposition: Lemma rotate_nat_add_lt base offset len : 0 < len → rotate_nat_add base offset len < len.
proof: Proof. unfold rotate_nat_add. intros ?. pose proof (Nat.mod_upper_bound (base + offset) len). rewrite Z2Nat.inj_mod, Z2Nat.inj_add, !Nat2Z.id; lia. Qed.
imports: Coq(QArith Qcanon) stdpp(well_founded) stdpp(options)