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