hfossli-agens

BOOL AGLineIntersection(AGLine l1, AGLine l2, AGPoint *out_pointOfIntersection)
{
    // http://stackoverflow.com/a/565282/202451

    AGPoint p = l1.start;
    AGPoint q = l2.start;
    AGPoint r = AGPointSubtract(l1.end, l1.start);
    AGPoint s = AGPointSubtract(l2.end, l2.start);
    
    double s_r_crossProduct = AGPointCrossProduct(r, s);

hfossli-agens

static void dispatch_repeated_internal(dispatch_time_t firstPopTime, double intervalInSeconds, dispatch_queue_t queue, void(^work)(BOOL *stop))
{    
    __block BOOL shouldStop = NO;
    dispatch_time_t nextPopTime = dispatch_time(firstPopTime, (int64_t)(intervalInSeconds * NSEC_PER_SEC));
    dispatch_after(nextPopTime, queue, ^{
        work(&shouldStop);
        if(!shouldStop)
        {
            dispatch_repeated_internal(nextPopTime, intervalInSeconds, queue, work);
        }