proposition: Lemma is_natE n : (0 <= n) = ((trunc n)%:R == n).
proof: Proof. by case: n => //= n; rewrite natz eqxx. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)