proposition: Lemma complB x y : ~` (x `\` y) = ~` x `|` y.
proof: Proof. by rewrite !complE diffxB meet1x. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)