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