diff -r 93dd862335af -r 3095ff2b5c18 src/lemon/full_graph.h
--- a/src/lemon/full_graph.h	Thu Nov 11 10:29:25 2004 +0000
+++ b/src/lemon/full_graph.h	Thu Nov 11 11:12:42 2004 +0000
@@ -17,6 +17,8 @@
 #ifndef LEMON_FULL_GRAPH_H
 #define LEMON_FULL_GRAPH_H
 
+#include <cmath>
+
 
 #include <lemon/iterable_graph_extender.h>
 #include <lemon/alteration_observer_registry.h>
@@ -197,8 +199,6 @@
   ///Thus it conforms to
   ///the \ref concept::StaticGraph "StaticGraph" concept
   ///\sa concept::StaticGraph.
-  ///\todo What about loops?
-  ///\todo Don't we need SymEdgeMap?
   ///
   ///\author Alpar Juttner
   class FullGraph : public MappableFullGraphBase {
@@ -207,6 +207,173 @@
     FullGraph(int n) { construct(n); }
   };
 
+
+  /// Base graph class for UndirFullGraph.
+
+  class UndirFullGraphBase {
+    int NodeNum;
+    int EdgeNum;
+  public:
+
+    typedef FullGraphBase Graph;
+
+    class Node;
+    class Edge;
+
+  public:
+
+    FullGraphBase() {}
+
+
+    ///Creates a full graph with \c n nodes.
+    void construct(int n) { NodeNum = n; EdgeNum = n * (n - 1) / 2; }
+    ///
+    //    FullGraphBase(const FullGraphBase &_g)
+    //      : NodeNum(_g.nodeNum()), EdgeNum(NodeNum*NodeNum) { }
+    
+    typedef True NodeNumTag;
+    typedef True EdgeNumTag;
+
+    ///Number of nodes.
+    int nodeNum() const { return NodeNum; }
+    ///Number of edges.
+    int edgeNum() const { return EdgeNum; }
+
+    /// Maximum node ID.
+    
+    /// Maximum node ID.
+    ///\sa id(Node)
+    int maxId(Node = INVALID) const { return NodeNum-1; }
+    /// Maximum edge ID.
+    
+    /// Maximum edge ID.
+    ///\sa id(Edge)
+    int maxId(Edge = INVALID) const { return EdgeNum-1; }
+
+    Node tail(Edge e) const { 
+      /// \todo we may do it faster
+      return ((int)sqrt((double)(1 + 8 * e.id)) + 1) / 2; 
+    }
+
+    Node head(Edge e) const { 
+      int tail = ((int)sqrt((double)(1 + 8 * e.id)) + 1) / 2;;
+      return e.id - (tail) * (tail - 1) / 2; 
+    }
+
+
+    /// Node ID.
+    
+    /// The ID of a valid Node is a nonnegative integer not greater than
+    /// \ref maxNodeId(). The range of the ID's is not surely continuous
+    /// and the greatest node ID can be actually less then \ref maxNodeId().
+    ///
+    /// The ID of the \ref INVALID node is -1.
+    ///\return The ID of the node \c v. 
+
+    static int id(Node v) { return v.id; }
+    /// Edge ID.
+    
+    /// The ID of a valid Edge is a nonnegative integer not greater than
+    /// \ref maxEdgeId(). The range of the ID's is not surely continuous
+    /// and the greatest edge ID can be actually less then \ref maxEdgeId().
+    ///
+    /// The ID of the \ref INVALID edge is -1.
+    ///\return The ID of the edge \c e. 
+    static int id(Edge e) { return e.id; }
+
+    /// Finds an edge between two nodes.
+    
+    /// Finds an edge from node \c u to node \c v.
+    ///
+    /// If \c prev is \ref INVALID (this is the default value), then
+    /// It finds the first edge from \c u to \c v. Otherwise it looks for
+    /// the next edge from \c u to \c v after \c prev.
+    /// \return The found edge or INVALID if there is no such an edge.
+    Edge findEdge(Node u,Node v, Edge prev = INVALID) 
+    {
+      return prev.id == -1 ? Edge(*this, u.id, v.id) : INVALID;
+    }
+    
+      
+    class Node {
+      friend class FullGraphBase;
+
+    protected:
+      int id;
+      Node(int _id) { id = _id;}
+    public:
+      Node() {}
+      Node (Invalid) { id = -1; }
+      bool operator==(const Node node) const {return id == node.id;}
+      bool operator!=(const Node node) const {return id != node.id;}
+      bool operator<(const Node node) const {return id < node.id;}
+    };
+    
+
+
+    class Edge {
+      friend class FullGraphBase;
+      
+    protected:
+      int id;  // NodeNum * head + tail;
+
+      Edge(int _id) : id(_id) {}
+
+      Edge(const FullGraphBase& _graph, int tail, int head) 
+	: id(_graph.NodeNum * head+tail) {}
+    public:
+      Edge() { }
+      Edge (Invalid) { id = -1; }
+      bool operator==(const Edge edge) const {return id == edge.id;}
+      bool operator!=(const Edge edge) const {return id != edge.id;}
+      bool operator<(const Edge edge) const {return id < edge.id;}
+    };
+
+    void first(Node& node) const {
+      node.id = NodeNum-1;
+    }
+
+    static void next(Node& node) {
+      --node.id;
+    }
+
+    void first(Edge& edge) const {
+      edge.id = EdgeNum-1;
+    }
+
+    static void next(Edge& edge) {
+      --edge.id;
+    }
+
+    void firstOut(Edge& edge, const Node& node) const {      
+      edge.id = node.id != 0 ? node.id * (node.id - 1) / 2 : -1;
+    }
+
+    /// \todo with specialized iterators we can make faster iterating
+    void nextOut(Edge& edge) const {
+      int tail = ((int)sqrt((double)(1 + 8 * e.id)) + 1) / 2;;
+      int head = e.id - (tail) * (tail - 1) / 2; 
+      ++head;
+      return head < tail ? tail * (tail - 1) / 2 + head : -1;
+    }
+
+    void firstIn(Edge& edge, const Node& node) const {
+      edge.id = node.id * (node.id + 1) / 2 - 1;
+    }
+    
+    void nextIn(Edge& edge) const {
+      int tail = ((int)sqrt((double)(1 + 8 * e.id)) + 1) / 2;;
+      int head = e.id - (tail) * (tail - 1) / 2; ++head;
+      ++tail;
+      return tail < nodeNum ? tail * (tail - 1) / 2 + head : -1;
+    }
+
+  };
+
+  /// \todo UndirFullGraph from the UndirFullGraphBase
+
+  
+
   /// @}  
 
 } //namespace lemon