proposition: Lemma msetIS C A B : A `<=` B -> C `&` A `<=` C `&` B.
proof: Proof. move=> sAB; apply/msubsetP=> x; rewrite !msetE. by rewrite leq_min !geq_min leqnn (msubsetP sAB) orbT. Qed.
imports: mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop tuple) finmap