proposition: Lemma intrEge0 x : 0 <= x -> (x \is a int_num) = (x \is a nat_num).
proof: Proof. by rewrite natrEint andbC => ->. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop order ssralg poly ssrnum ssrint)