- Real w = me->get_bound (LEFT)->relative_coordinate (common, X_AXIS)
- - me->get_bound (RIGHT)->relative_coordinate (common, X_AXIS);
+
+ Interval rext = me->get_bound (RIGHT)->extent (common, X_AXIS);
+
+
+ Real w =(rext.empty_b()
+ ? me->get_bound (RIGHT)->relative_coordinate (common, X_AXIS)
+ : rext[RIGHT])
+ - me->get_bound (LEFT)->relative_coordinate (common, X_AXIS);