- virtual Array<Rod> get_rods () const;
- virtual Array<Spring> get_springs () const;
- virtual Score_element* find_broken_piece (Line_of_score*) const;
- virtual void do_derived_mark ();
+ virtual Grob* find_broken_piece (System*) const;
+ virtual SCM do_derived_mark ();
+ static bool has_interface (Grob*);