proposition: Lemma Exists_one_eq : forall P x, Exists P (x::nil) = P x.
proof: Proof. Proof using. intros. extens. rewrite Exists_cons_eq. rewrite* Exists_nil_eq. Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)