Version: 5.6
public static float PingPong (float t, float length);


PingPongs the value t, so that it is never larger than length and never smaller than 0.

The returned value will move back and forth between 0 and length.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour { void Update() { transform.position = new Vector3(Mathf.PingPong(Time.time, 3), transform.position.y, transform.position.z); } }