+extern gboolean cylinder_none(void *_data);
+extern gboolean no_cylinders(cylinder_t *cyl);
+extern gboolean cylinders_equal(cylinder_t *cyl1, cylinder_t *cyl2);
+extern gboolean no_weightsystems(weightsystem_t *ws);
+extern gboolean weightsystems_equal(weightsystem_t *ws1, weightsystem_t *ws2);