proposition: Lemma natr_gt0 x : x \is a nat_num -> (0 < x) = (x != 0).
proof: Proof. by move=> /natrP[n ->]; rewrite pnatr_eq0 ltr0n lt0n. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop order ssralg poly ssrnum ssrint)