proposition: Lemma msetIIr A B C : A `&` (B `&` C) = (A `&` B) `&` (A `&` C).
proof: Proof. by rewrite !(msetIC A) msetIIl. Qed.
imports: mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop tuple) finmap