proposition: Lemma is_intE n : true = (0 <= n) || (0 <= - n).
proof: Proof. by case: n. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)