+ Real distance (Skyline const &, Real horizon_padding = 0) const;
+ Real touching_point (Skyline const &, Real horizon_padding = 0) const;
+ Real shift_to_avoid (Skyline const &other, Real, Direction d, Real horizon_padding = 0);
+ Real raise_to_avoid (Skyline const &other, Real, Direction d, Real horizon_padding = 0);
+ Drul_array<Real> shifts_to_avoid_intersection (Skyline const &, Real horizon_padding = 0) const;
+ Interval raises_to_avoid_intersection (Skyline const &, Real horizon_padding = 0) const;