Qed.
End Co_Induction_ForAll.
End Stream_Properties.
End Streams.
Section Map.
Variables A B : Type.
Variable f : A -> B.
CoFixpoint map (s:Stream A) : Stream B := Cons (f (hd s)) (map (tl s)).

Lemma Exists_map : forall (P:Stream B -> Prop) (S:Stream A), Exists (fun s => P
(map s)) S -> Exists P (map S).