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 cylinder_none(void *_data);
extern gboolean no_cylinders(cylinder_t *cyl);
extern gboolean cylinders_equal(cylinder_t *cyl1, cylinder_t *cyl2);