proposition: Lemma BZ_of_Z_neg p: BZ_of_Z (Negz p) = BZopp (BZ_of_Z (Posz p.+1)).
proof: Proof. by rewrite /= /BZopp /BZ_of_nat/int_np; aw; Ytac0. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype order) mathcomp(ssrnat ssrint ssralg ssrnum div)