Grob *common = common_refpoint_of_array (ordered_rests[DOWN], me, Y_AXIS);
common = common_refpoint_of_array (ordered_rests[UP], common, Y_AXIS);
Grob *common = common_refpoint_of_array (ordered_rests[DOWN], me, Y_AXIS);
common = common_refpoint_of_array (ordered_rests[UP], common, Y_AXIS);