proposition: Lemma fdisjointP_sym {A B} : reflect (forall a, a \in A -> a \notin B) [disjoint B & A]%fset.
proof: Proof. by rewrite fdisjoint_sym; apply: fdisjointP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)