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