proposition: Lemma toNat_zero n : toNat (zero n) = 0.
proof: Proof. induction n => //. rewrite /toNat/=. rewrite /toNat in IHn. by rewrite IHn. Qed.
imports: Coq(ZArith.ZArith) mathcomp.ssreflect.ssreflect mathcomp(ssrfun ssrbool eqtype ssrnat seq fintype tuple div zmodp ssralg) ssrextra.nat ssrextra.tuple spec.spec