[FIXED] Angle difference between -180 and 180

Issue

I know a way to find the angle difference of two angles between [0,180], but I'm trying to find out a way to find the angle difference of two angles between [-179,180].

My code is as follows; it doesn't work properly:

private int distance2(int alpha, int beta) {
    int phi = beta - alpha;// % 360;    // This is either the distance or 360 - distance
    int distance = 0;
    if (phi < -360) {
        distance = 360 + phi;
    } // end of if
    else{
        distance = phi;  
    }
    return distance;
}

Solution

If you are sure that alpha and beta are both in [-180, 180] interval, you know

-360 <= alpha - beta <= 360

So you can use:

private int distance2(int alpha, int beta) {
    int distance = beta - alpha;      // This is the distance mod 360
    if (phi <= -180) {
        distance += 360; // you were between -360 and -180 -> 0 <= distance <= 180
    else if (phi > 180) {
        distance -= 360; // you were between 180 and 360 -> 180 < distance <= 0
    }
    return distance;
}

If you cannot be sure of input values, just replace first line with:

int distance = (beta - alpha) % 360;  // forces distance in ]-360, 360[ range

Answered By - Serge Ballesta
Answer Checked By - Cary Denson (JavaFixing Admin)