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