+class Skyline_pair
+{
+private:
+ Drul_array<Skyline> skylines_;
+
+ DECLARE_SIMPLE_SMOBS(Skyline_pair);
+public:
+ Skyline_pair ();
+ Skyline_pair (vector<Box> const &boxes, Real horizon_padding, Axis a);
+ Skyline_pair (Box const &, Real horizon_padding, Axis a);
+ void raise (Real);
+ void shift (Real);
+ void insert (Box const &, Real horizon_padding, Axis);
+ void merge (Skyline_pair const &other);
+ Skyline &operator [] (Direction d);
+ Skyline const &operator [] (Direction d) const;
+ bool is_empty () const;
+};