+IMPLEMENT_CTOR_CALLBACK (Music_iterator);
+
+Music *
+Music_iterator::get_music () const
+{
+ return music_;
+}
+
+/****************************************************************/
+
+IMPLEMENT_TYPE_P (Music_iterator, "ly:iterator?");
+IMPLEMENT_SMOBS (Music_iterator);
+IMPLEMENT_DEFAULT_EQUAL_P (Music_iterator);
+
+SCM
+Music_iterator::mark_smob (SCM smob)
+{
+ Music_iterator *mus = (Music_iterator *)SCM_CELL_WORD_1 (smob);
+
+ mus->derived_mark ();
+ /*
+ Careful with GC, although we intend the following as pointers
+ only, we _must_ mark them.
+ */
+ if (mus->get_outlet ())
+ scm_gc_mark (mus->get_outlet ()->self_scm ());
+ if (mus->music_)
+ scm_gc_mark (mus->music_->self_scm ());
+
+ return SCM_EOL;
+}
+
+int
+Music_iterator::print_smob (SCM sm, SCM port, scm_print_state *)
+{
+ char s[1000];
+
+ Music_iterator *iter = unsmob_iterator (sm);
+ sprintf (s, "#<%s>", iter->class_name ());
+ scm_puts (s, port);
+ return 1;
+}
+
+void
+Music_iterator::derived_mark ()const
+{
+}
+
+void
+Music_iterator::quit ()
+{
+ do_quit ();
+ handle_.set_context (0);
+}
+
+void
+Music_iterator::do_quit ()
+{
+}
+
+bool
+Music_iterator::run_always ()const
+{
+ return false;
+}
+
+bool
+is_child_context (Context *me, Context *child)
+{
+ while (child && child != me)
+ child = child->get_parent_context ();
+
+ return child == me;
+}
+
+/*
+ move to context of child iterator if it is deeper down in the
+ hierarchy.
+*/
+void
+Music_iterator::descend_to_child (Context *child_report)
+{
+ Context *me_report = get_outlet ();
+ if (is_child_context (me_report, child_report))
+ set_context (child_report);
+}