proposition: Lemma setD_eq0 A B : (A :\: B == set0) = (A \subset B).
proof: Proof. by rewrite -subset0 subDset setU0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop)