proposition: Lemma normr_sgz x : `|sgz x| = (x != 0).
proof: Proof. by rewrite sgz_def -mulr_natr normrMsign normr_nat natz. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)