Interval_t<int> rank_span = g->spanned_rank_interval ();
if (rank_span[LEFT] <= end && rank_span[RIGHT] >= start
&& g->pure_is_visible (start, end)
Interval_t<int> rank_span = g->spanned_rank_interval ();
if (rank_span[LEFT] <= end && rank_span[RIGHT] >= start
&& g->pure_is_visible (start, end)