I am trying to wrap the angle to be within the range of [-pi, pi]. I have tried many variations of the following code, it should be a very easy task, however, if the angle is already pi, -pi, or 0, it outputs it as negative (so pi = -pi, -pi = pi, 0 = -0).

Here is the code I currently have:

static double wrapAngle( double angle){
    while (angle < -M_PI) {
        angle += 2.0 * M_PI;
    }
    while (angle > M_PI) {
        angle -= 2.0 * M_PI;
    }
    return angle;
}

It correctly wraps everything except -M_PI, M_PI, and 0. It gives me the negative.