proposition: Lemma tail_set : forall A : Type, forall (P : A -> Type), forall a, forall l, (forall b, In b (a::l) -> P b) -> (forall b, In b l -> P b).
proof: Proof. intros Ar P a l H b In_b; apply H; right; trivial. Qed.
imports: Coq(Bool List Arith Setoid Relations FunInd) CoLoR(closure)