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