proposition: Lemma sgz_cp0 x : ((sgz x == 1) = (0 < x)) * ((sgz x == -1) = (x < 0)) * ((sgz x == 0) = (x == 0)).
proof: Proof. by rewrite /sgz; case: ltrgtP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)