proposition: Lemma Forall_drop : forall P n l, Forall P l -> Forall P (drop n l).
proof: Proof. Proof using. introv E. forwards (q&K): drop_is_suffix n l. rewrite K in E. rewrite* Forall_app_eq in E. Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)