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