proposition: Lemma disjointWr A B C : A \subset B -> [disjoint C & B] -> [disjoint C & A].
proof: Proof. rewrite ![[disjoint C & _]]disjoint_sym. exact:disjointWl. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(path div)