lukewakeford

func sortConvex(input: [CLLocationCoordinate2D]) -> [CLLocationCoordinate2D] {
        
        // X = longitude
        // Y = latitudeß
        
        // 2D cross product of OA and OB vectors, i.e. z-component of their 3D cross product.
        // Returns a positive value, if OAB makes a counter-clockwise turn,
        // negative for clockwise turn, and zero if the points are collinear.
        func cross(P: CLLocationCoordinate2D, A: CLLocationCoordinate2D, B: CLLocationCoordinate2D) -> Double {
            let part1 = (A.longitude - P.longitude) * (B.latitude - P.latitude)