proposition: Lemma sgzN1 : sgz (-1 : R) = -1.
proof: Proof. by rewrite ltr0_sgz // ltrN10. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)