proposition: Lemma setD_eq0 A B : (A `\` B == mset0) = (A `<=` B).
proof: Proof. by rewrite -msubset0 subset_msetBLR msetD0. Qed.
imports: mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop tuple) finmap