+Interval_t<Moment>
+spanned_time_interval (Item *l, Item *r)
+{
+ Drul_array<Item*> bounds (l, r);
+ Interval_t<Moment> iv;
+
+ Direction d = LEFT;
+ do
+ {
+ if (bounds[d] && bounds[d]->get_column ())
+ iv[d] = robust_scm2moment (bounds[d]->get_column ()->get_property ("when"),
+ iv[d]);
+ }
+ while (flip (&d) != LEFT);
+
+ do
+ {
+ if (!bounds[d] || !bounds[d]->get_column ())
+ iv[d] = iv[-d];
+ }
+ while (flip (&d) != LEFT);
+
+
+ return iv;
+}
+
+