AnimationCurve error and solution

Hi,
I read the documentation about animation curves, here : http://docs.unity3d.com/ScriptReference/AnimationCurve-ctor.html
When I tried to run the supplied script, I got the following error :

It is easy to fix, by creating a new Vector3. If you use this code though and apply it on a cube, you will see the cube going up and to the right, disappearing from the screen.
Perhaps using the WrapMode as follows could provide a more interesting example. You get a cube that goes up and down. User can modify the curve characteristics in Editor during runtime and watch how the cube motion changes.

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class AnimCurveExample : MonoBehaviour
5. {
6.     public AnimationCurve curve ;
7.    
8.     void Start()
9.     {
10.         curve = new AnimationCurve(new Keyframe(0, 0), new Keyframe(1, 1));
11.         curve.preWrapMode = WrapMode.PingPong;
12.         curve.postWrapMode = WrapMode.PingPong;
13.     }
14.    
15.     void Update()
16.     {
17.         transform.position = new Vector3(transform.position.x, curve.Evaluate(Time.time), transform.position.z);
18.     }
19. }