proposition: Theorem fold_length_correct : forall X (l : list X), fold_length l = length l.
proof: Proof. Admitted. Definition fold_map {X Y:Type} (f : X -> Y) (l : list X) : list Y . Admitted. Definition prod_curry {X Y Z : Type} (f : X * Y -> Z) (x : X) (y : Y) : Z := f (x, y). Definition prod_uncurry {X Y Z : Type} (f : X -> Y -> Z) (p : X * Y) : Z . Admitted. Example test_map1': map (plus 3) [2;0;2] = [5;3;5]. MProof. reflexivity. Qed.