proposition: Lemma toNat_zeroExtendAux extra n (p: BITS n) : toNat (zeroExtendAux extra p) = toNat p.
proof: Proof. induction extra => //. by rewrite /= toNat_joinmsb0 IHextra. 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