#include <lemon/list_graph.h>

 #include <lemon/graph_utils.h>

 #include <lemon/xy.h>

 #include <lemon/graph_to_eps.h>

 #include <cstdlib>

 #include <cmath>

 #include <ctime>

 using namespace lemon;

 // Special map type

 // It gives back a position for each node. The position of the nodes 

 // are on the circle with the given center and radius.

 //

 // Because we use the descriptor map it will hold the proprty described above

 // even if a node added or deleted. 

 template <typename Graph>

 class CircleMap {

 public:

   typedef xy<double> Value;

   typedef typename Graph::Node Key;

   CircleMap(const Graph& _graph, 

 	    const Value& _center = Value(0.0, 0.0), 

 	    double _radius = 1.0) 

     : descriptor(_graph), center(_center), radius(_radius) {}

   Value operator[](const Key& key) const {

     double angle = descriptor[key] * 2 * M_PI 

       / (double)descriptor.inverse().size();

     double x = std::cos(angle) * radius + center.x;

     double y = std::sin(angle) * radius + center.y;

     return Value(x, y);

   }

 private:

   DescriptorMap<Graph, typename Graph::Node> descriptor;

   Value center;

   double radius;

 };

 int main() {

   std::srand(std::time(0));

   typedef ListGraph Graph;

   typedef Graph::Node Node;

   typedef Graph::Edge Edge;

   // Generating a graph

   Graph graph;

   const int NODE = 16;

   for (int i = 0; i < NODE; ++i) {

     graph.addNode();

   } 

   // Creating descriptor map and inverse

   DescriptorMap<Graph, Node> nodeDesc(graph);

   DescriptorMap<Graph, Node>::InverseMap nodeInv(nodeDesc);

   // Adding edges

   // The descriptor map always maps an integer value for each node.

   // The range of the values is always [0..n - 1] where n is the

   // number of the nodes of the graph. The inverse map gives back the

   // the node by its descriptor value. 

   //

   // The inversemap cannot works without its DescriptorMap because

   // it holds reference to it. 

   const int EDGE = (int)(NODE * std::log(NODE));

   for (int i = 0; i < EDGE; ++i) {

     int si = (int)(std::rand() / (RAND_MAX + 1.0) * NODE);

     int ti = (int)(std::rand() / (RAND_MAX + 1.0) * NODE);

     graph.addEdge(nodeInv[si], nodeInv[ti]);

   }

   // Make postscript from the graph.

   CircleMap<Graph> coords(graph, xy<double>(0.0, 0.0), 10.0);

   graphToEps(graph,"descriptor_map_demo.eps").scaleToA4().

     title("Generated graph").

     copyright("(C) 2005 LEMON Project").

     coords(coords).

     nodeScale(1.0).

     enableParallel().parEdgeDist(1).

     drawArrows().arrowWidth(1).arrowLength(1).

     run();

   return 0;

 }