> but if we only check the correctness at the end, then isn't it possible that it already collided with an obstacle? You would put the check before it actually

> but if we only check the correctness at the end, then isn't it possible that it already collided with an obstacle? You would put the check before it actually does the thing. It's at the "end" of the process of figuring out what it wants to do, not the end of fulfilling the request or prompt