# HG changeset patch
# User deba
# Date 1121263549 0
# Node ID 434f9add42cdc0909409b6f4e8f4781a16467468
# Parent  5c7f270f8e25c814426d8ce0376a9e553925226a
Demo about descriptor map.

diff -r 5c7f270f8e25 -r 434f9add42cd demo/descriptor_map_demo.cc
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/demo/descriptor_map_demo.cc	Wed Jul 13 14:05:49 2005 +0000
@@ -0,0 +1,95 @@
+#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;
+}