proposition: Lemma msetUIl A B C : (A `&` B) `|` C = (A `|` C) `&` (B `|` C).
proof: Proof. by apply/msetP=> x; rewrite !msetE maxn_minl. Qed.
imports: mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop tuple) finmap