hpts_slots_diff
slots_to_run = hpts_slots_diff(hpts->p_prev_slot, hpts->p_cur_slot);
return(hpts_slots_diff(slot_pos_of_endpoint, orig_exit_slot));
dis_to_travel = hpts_slots_diff(hpts->p_prev_slot, wheel_slot);
dis_to_travel = hpts_slots_diff(hpts->p_runningslot, hpts->p_cur_slot);
pacer_to_now = hpts_slots_diff(hpts->p_cur_slot, wheel_slot);
distance = hpts_slots_diff(hpts->p_runningslot, hptsslot);
yet_to_run = hpts_slots_diff(hpts->p_runningslot, hpts->p_cur_slot);
have_slept = hpts_slots_diff(hpts->p_prev_slot, wheel_slot);