BCE0023: No appropriate version of 'UnityEngine.Mathf.SmoothDamp' for the argument list '(float, int, Object, float)' was found.

I get the error : “BCE0023: No appropriate version of ‘UnityEngine.Mathf.SmoothDamp’ for the argument list ‘(float, int, Object, float)’ was found.” when using the following code to move the gun from the hip to the aiming position.

if (Input.GetButton("Fire2"))
	ratioHipHold = Mathf.SmoothDamp(ratioHipHold, 0, ratioHipHoldV, hipToAimSpeed);
if (Input.GetButton("Fire2") == false)
	ratioHipHold = Mathf.SmoothDamp(ratioHipHold, 1, ratioHipHoldV, hipToAimSpeed);

Edit: Here you go:

var ratioHipHold : float = 1;
var hipToAimSpeed : float = 0.1;
@HideInInspector
var ratioHipHoldV;

You must always define the type of variables, either explicitly or by supplying a value.