Added an example

Spatial_sorting/examples/Spatial_sorting/sort_indices.cpp

@@ -0,0 +1,81 @@
+
+#include <CGAL/Simple_cartesian.h>
+#include <CGAL/spatial_sort.h>
+
+
+typedef CGAL::Simple_cartesian<double> K;
+typedef K::Point_2 Point_2;
+typedef std::vector<Point_2>::iterator Point_iterator;
+
+
+
+template <typename Kernel, typename Iterator>
+struct Sort_traits_2 {
+
+  typedef Iterator Point_2;
+
+  struct Less_x_2 {
+    bool operator() (const Point_2 &p, const Point_2 &q) const
+    { 
+      K k;
+      std::cout << "compare " << *p << "  and " << *q << std::endl;
+      return k.less_x_2_object() (*p, *q);
+    } 
+  };
+
+  Less_x_2
+  less_x_2_object() const
+  {
+    return Less_x_2();
+  }
+  
+  struct Less_y_2 {
+    bool operator() (const Point_2 &p, const Point_2 &q) const
+    { 
+      K k;
+      return k.less_y_2_object() (*p, *q);
+    } 
+  };
+
+
+  Less_y_2
+  less_y_2_object() const
+  {
+    return Less_y_2();
+  }
+};
+
+
+typedef CGAL::Hilbert_sort_2<Sort_traits_2<K, Point_iterator> > Hilbert_sort_2;
+typedef CGAL::Multiscale_sort<Hilbert_sort_2> Spatial_sort_2;
+
+
+
+
+int main ()
+{
+  Spatial_sort_2 sort_2;
+
+  std::vector<Point_2> points;
+  std::vector<Point_iterator> iterators;
+
+  Point_2 p;
+  while(std::cin >> p){
+    points.push_back(p);
+  }
+
+  iterators.reserve(points.size());
+  for(Point_iterator it = points.begin(); it != points.end(); ++it){
+    iterators.push_back(it);
+  }
+
+  sort_2(iterators.begin(), iterators.end());
+
+  for(int i = 0; i < iterators.size(); i++){
+    std::cout << *iterators[i] << std::endl;
+  }
+
+  std::cout << "done" << std::endl;
+
+  return 0;
+}