- static int compare (Spanner * const &,Spanner * const &);
- virtual Grob* find_broken_piece (Line_of_score*) const;
- virtual SCM do_derived_mark ();
+ static int compare (Spanner *const &, Spanner *const &);
+ static bool less (Spanner *const &, Spanner *const &);
+ virtual Grob *find_broken_piece (System *) const;
+ virtual void derived_mark () const;
+ DECLARE_GROB_INTERFACE();
+ virtual System *get_system () const;
+