proposition: Lemma natr_ge0 x : x \is a nat_num -> 0 <= x.
proof: Proof. by move=> /natrP[n ->]; apply: ler0n. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop order ssralg poly ssrnum ssrint)