Jumping with touch input.

Hey. So I am using a script that allows a ball to rotate with the horizontal axis, and it has a jumping feature built in. (SPACE BAR) when I change it from

 (Input.GetKeyDown(KeyCode.Space)

to

 (Input.GetTouch(0)

I get the following compiler error.

UnityEngine.touch cannot be used in a boolean context

If you want the code for the jumping & moving thing to modify it, here it is. PS the spacebar works fine.

 #pragma strict
 
 var rotationSpeed = 100;
 var jumpHeight = 8;
 
 private var isFalling = false;
 
 function Update ()
 {
     //Handle ball rotation.
     var rotation : float = Input.GetAxis ("Horizontal") * rotationSpeed;
     rotation *= Time.deltaTime;
     rigidbody.AddRelativeTorque (Vector3.back * rotation);
     
     if (Input.GetTouch(0) && isFalling == false)
     {
         rigidbody.velocity.y = jumpHeight;
     }
     isFalling = true;
 }
 
 function OnCollisionStay ()
 {
     isFalling = false;
 }