proposition: Lemma Nth_Exists : forall P n l x, Nth n l x -> P x -> Exists P l.
proof: Proof. Proof using. introv M H. applys* mem_Exists. applys* Nth_mem. Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)