proposition: Lemma lexC x y : (x <= ~` y) = (y <= ~` x).
proof: Proof. by rewrite !complE !leBRL !lex1 meetC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)