source: lemon-0.x/src/work/alpar/list_graph.h @ 410:d137525538dc

// -*- mode:C++ -*-

#ifndef HUGO_LIST_GRAPH_H
#define HUGO_LIST_GRAPH_H

///ingroup graphs
///\file
///\brief ListGraph, SymListGraph, NodeSet and EdgeSet classes.

#include <vector>
#include <limits.h>

#include "invalid.h"

namespace hugo {

/// \addtogroup graphs
/// @{

  class SymListGraph;

  ///A list graph class.

  ///This is a simple and fast erasable graph implementation.
  ///
  ///It conforms to the graph interface documented under
  ///the description of \ref GraphSkeleton.
  ///\sa \ref GraphSkeleton.
  class ListGraph {

    //Nodes are double linked.
    //The free nodes are only single linked using the "next" field.
    struct NodeT 
    {
      int first_in,first_out;
      int prev, next;
      //      NodeT() {}
    };
    //Edges are double linked.
    //The free edges are only single linked using the "next_in" field.
    struct EdgeT 
    {
      int head, tail;
      int prev_in, prev_out;
      int next_in, next_out;
      //FIXME: is this necessary?
      //      EdgeT() : next_in(-1), next_out(-1) prev_in(-1), prev_out(-1) {}  
    };

    std::vector<NodeT> nodes;
    //The first node
    int first_node;
    //The first free node
    int first_free_node;
    std::vector<EdgeT> edges;
    //The first free edge
    int first_free_edge;
    
  protected:
    
    template <typename Key> class DynMapBase
    {
    protected:
      const ListGraph* G; 
    public:
      virtual void add(const Key k) = NULL;
      virtual void erase(const Key k) = NULL;
      DynMapBase(const ListGraph &_G) : G(&_G) {}
      virtual ~DynMapBase() {}
      friend class ListGraph;
    };
    
  public:
    template <typename T> class EdgeMap;
    template <typename T> class NodeMap;
    
    class Node;
    class Edge;

    //  protected:
    // HELPME:
  protected:
    ///\bug It must be public because of SymEdgeMap.
    ///
    mutable std::vector<DynMapBase<Node> * > dyn_node_maps;
    ///\bug It must be public because of SymEdgeMap.
    ///
    mutable std::vector<DynMapBase<Edge> * > dyn_edge_maps;
    
  public:

    class NodeIt;
    class EdgeIt;
    class OutEdgeIt;
    class InEdgeIt;
    
    template <typename T> class NodeMap;
    template <typename T> class EdgeMap;
    
  public:

    ListGraph() : nodes(), first_node(-1),
                  first_free_node(-1), edges(), first_free_edge(-1) {}
    ListGraph(const ListGraph &_g) : nodes(_g.nodes), first_node(_g.first_node),
                                     first_free_node(_g.first_free_node),
                                     edges(_g.edges),
                                     first_free_edge(_g.first_free_edge) {}
    
    ~ListGraph()
    {
      for(std::vector<DynMapBase<Node> * >::iterator i=dyn_node_maps.begin();
          i!=dyn_node_maps.end(); ++i) (**i).G=NULL;
      for(std::vector<DynMapBase<Edge> * >::iterator i=dyn_edge_maps.begin();
          i!=dyn_edge_maps.end(); ++i) (**i).G=NULL;
    }

    int nodeNum() const { return nodes.size(); }  //FIXME: What is this?
    int edgeNum() const { return edges.size(); }  //FIXME: What is this?

    ///\bug This function does something different than
    ///its name would suggests...
    int maxNodeId() const { return nodes.size(); }  //FIXME: What is this?
    ///\bug This function does something different than
    ///its name would suggests...
    int maxEdgeId() const { return edges.size(); }  //FIXME: What is this?

    Node tail(Edge e) const { return edges[e.n].tail; }
    Node head(Edge e) const { return edges[e.n].head; }

    Node aNode(OutEdgeIt e) const { return edges[e.n].tail; }
    Node aNode(InEdgeIt e) const { return edges[e.n].head; }

    Node bNode(OutEdgeIt e) const { return edges[e.n].head; }
    Node bNode(InEdgeIt e) const { return edges[e.n].tail; }

    NodeIt& first(NodeIt& v) const { 
      v=NodeIt(*this); return v; }
    EdgeIt& first(EdgeIt& e) const { 
      e=EdgeIt(*this); return e; }
    OutEdgeIt& first(OutEdgeIt& e, const Node v) const { 
      e=OutEdgeIt(*this,v); return e; }
    InEdgeIt& first(InEdgeIt& e, const Node v) const { 
      e=InEdgeIt(*this,v); return e; }

//     template< typename It >
//     It first() const { It e; first(e); return e; }

//     template< typename It >
//     It first(Node v) const { It e; first(e,v); return e; }

    bool valid(Edge e) const { return e.n!=-1; }
    bool valid(Node n) const { return n.n!=-1; }
    
    void setInvalid(Edge &e) { e.n=-1; }
    void setInvalid(Node &n) { n.n=-1; }
    
    template <typename It> It getNext(It it) const
    { It tmp(it); return next(tmp); }

    NodeIt& next(NodeIt& it) const { 
      it.n=nodes[it.n].next; 
      return it; 
    }
    OutEdgeIt& next(OutEdgeIt& it) const
    { it.n=edges[it.n].next_out; return it; }
    InEdgeIt& next(InEdgeIt& it) const
    { it.n=edges[it.n].next_in; return it; }
    EdgeIt& next(EdgeIt& it) const {
      if(edges[it.n].next_in!=-1) { 
        it.n=edges[it.n].next_in;
      }
      else {
        int n;
        for(n=nodes[edges[it.n].head].next;
            n!=-1 && nodes[n].first_in == -1;
            n = nodes[n].next) ;
        it.n = (n==-1)?-1:nodes[n].first_in;
      }
      return it;
    }

    int id(Node v) const { return v.n; }
    int id(Edge e) const { return e.n; }

    /// Adds a new node to the graph.

    /// \todo It adds the nodes in a reversed order.
    /// (i.e. the lastly added node becomes the first.)
    Node addNode() {
      int n;
      
      if(first_free_node==-1)
        {
          n = nodes.size();
          nodes.push_back(NodeT());
        }
      else {
        n = first_free_node;
        first_free_node = nodes[n].next;
      }
      
      nodes[n].next = first_node;
      if(first_node != -1) nodes[first_node].prev = n;
      first_node = n;
      nodes[n].prev = -1;
      
      nodes[n].first_in = nodes[n].first_out = -1;
      
      Node nn; nn.n=n;

      //Update dynamic maps
      for(std::vector<DynMapBase<Node> * >::iterator i=dyn_node_maps.begin();
          i!=dyn_node_maps.end(); ++i) (**i).add(nn);

      return nn;
    }
    
    Edge addEdge(Node u, Node v) {
      int n;
      
      if(first_free_edge==-1)
        {
          n = edges.size();
          edges.push_back(EdgeT());
        }
      else {
        n = first_free_edge;
        first_free_edge = edges[n].next_in;
      }
      
      edges[n].tail = u.n; edges[n].head = v.n;

      edges[n].next_out = nodes[u.n].first_out;
      if(nodes[u.n].first_out != -1) edges[nodes[u.n].first_out].prev_out = n;
      edges[n].next_in = nodes[v.n].first_in;
      if(nodes[v.n].first_in != -1) edges[nodes[v.n].first_in].prev_in = n;
      edges[n].prev_in = edges[n].prev_out = -1;
        
      nodes[u.n].first_out = nodes[v.n].first_in = n;

      Edge e; e.n=n;

      //Update dynamic maps
      for(std::vector<DynMapBase<Edge> * >::iterator i=dyn_edge_maps.begin();
          i!=dyn_edge_maps.end(); ++i) (**i).add(e);

      return e;
    }

  private:
    void eraseEdge(int n) {
      
      if(edges[n].next_in!=-1)
        edges[edges[n].next_in].prev_in = edges[n].prev_in;
      if(edges[n].prev_in!=-1)
        edges[edges[n].prev_in].next_in = edges[n].next_in;
      else nodes[edges[n].head].first_in = edges[n].next_in;
      
      if(edges[n].next_out!=-1)
        edges[edges[n].next_out].prev_out = edges[n].prev_out;
      if(edges[n].prev_out!=-1)
        edges[edges[n].prev_out].next_out = edges[n].next_out;
      else nodes[edges[n].tail].first_out = edges[n].next_out;
      
      edges[n].next_in = first_free_edge;
      first_free_edge = -1;      

      //Update dynamic maps
      Edge e; e.n=n;
      for(std::vector<DynMapBase<Edge> * >::iterator i=dyn_edge_maps.begin();
          i!=dyn_edge_maps.end(); ++i) (**i).erase(e);
    }
      
  public:

    void erase(Node nn) {
      int n=nn.n;
      
      int m;
      while((m=nodes[n].first_in)!=-1) eraseEdge(m);
      while((m=nodes[n].first_out)!=-1) eraseEdge(m);

      if(nodes[n].next != -1) nodes[nodes[n].next].prev = nodes[n].prev;
      if(nodes[n].prev != -1) nodes[nodes[n].prev].next = nodes[n].next;
      else first_node = nodes[n].next;
      
      nodes[n].next = first_free_node;
      first_free_node = n;

      //Update dynamic maps
      for(std::vector<DynMapBase<Node> * >::iterator i=dyn_node_maps.begin();
          i!=dyn_node_maps.end(); ++i) (**i).erase(nn);
    }
    
    void erase(Edge e) { eraseEdge(e.n); }

    ///\bug Dynamic maps must be updated!
    ///
    void clear() {
      nodes.clear();edges.clear();
      first_node=first_free_node=first_free_edge=-1;
    }

    class Node {
      friend class ListGraph;
      template <typename T> friend class NodeMap;
       
      friend class Edge;
      friend class OutEdgeIt;
      friend class InEdgeIt;
      friend class SymEdge;

    protected:
      int n;
      friend int ListGraph::id(Node v) const; 
      Node(int nn) {n=nn;}
    public:
      Node() {}
      Node (Invalid i) { n=-1; }
      bool operator==(const Node i) const {return n==i.n;}
      bool operator!=(const Node i) const {return n!=i.n;}
      bool operator<(const Node i) const {return n<i.n;}
    };
    
    class NodeIt : public Node {
      friend class ListGraph;
    public:
      NodeIt() : Node() { }
      NodeIt(Invalid i) : Node(i) { }
      NodeIt(const ListGraph& G) : Node(G.first_node) { }
    };

    class Edge {
      friend class ListGraph;
      template <typename T> friend class EdgeMap;

      //template <typename T> friend class SymListGraph::SymEdgeMap;      
      //friend Edge SymListGraph::opposite(Edge) const;
      
      friend class Node;
      friend class NodeIt;
    protected:
      int n;
      friend int ListGraph::id(Edge e) const;

      Edge(int nn) {n=nn;}
    public:
      Edge() { }
      Edge (Invalid) { n=-1; }
      bool operator==(const Edge i) const {return n==i.n;}
      bool operator!=(const Edge i) const {return n!=i.n;}
      bool operator<(const Edge i) const {return n<i.n;}
      ///\bug This is a workaround until somebody tells me how to
      ///make class \c SymListGraph::SymEdgeMap friend of Edge
      int &idref() {return n;}
      const int &idref() const {return n;}
    };
    
    class EdgeIt : public Edge {
      friend class ListGraph;
    public:
      EdgeIt(const ListGraph& G) : Edge() {
        int m;
        for(m=G.first_node;
            m!=-1 && G.nodes[m].first_in == -1; m = G.nodes[m].next);
        n = (m==-1)?-1:G.nodes[m].first_in;
      }
      EdgeIt (Invalid i) : Edge(i) { }
      EdgeIt() : Edge() { }
      ///\bug This is a workaround until somebody tells me how to
      ///make class \c SymListGraph::SymEdgeMap friend of Edge
      int &idref() {return n;}
    };
    
    class OutEdgeIt : public Edge {
      friend class ListGraph;
    public: 
      OutEdgeIt() : Edge() { }
      OutEdgeIt (Invalid i) : Edge(i) { }

      OutEdgeIt(const ListGraph& G,const Node v)
        : Edge(G.nodes[v.n].first_out) {}
    };
    
    class InEdgeIt : public Edge {
      friend class ListGraph;
    public: 
      InEdgeIt() : Edge() { }
      InEdgeIt (Invalid i) : Edge(i) { }
      InEdgeIt(const ListGraph& G,Node v) :Edge(G.nodes[v.n].first_in){}
    };

    template <typename T> class NodeMap : public DynMapBase<Node>
    {
      std::vector<T> container;

    public:
      typedef T ValueType;
      typedef Node KeyType;

      NodeMap(const ListGraph &_G) :
        DynMapBase<Node>(_G), container(_G.maxNodeId())
      {
        G->dyn_node_maps.push_back(this);
      }
      NodeMap(const ListGraph &_G,const T &t) :
        DynMapBase<Node>(_G), container(_G.maxNodeId(),t)
      {
        G->dyn_node_maps.push_back(this);
      }
      
      NodeMap(const NodeMap<T> &m) :
        DynMapBase<Node>(*m.G), container(m.container)
      {
        G->dyn_node_maps.push_back(this);
      }

      template<typename TT> friend class NodeMap;
 
      ///\todo It can copy between different types.
      ///
      template<typename TT> NodeMap(const NodeMap<TT> &m) :
        DynMapBase<Node>(*m.G)
      {
        G->dyn_node_maps.push_back(this);
        typename std::vector<TT>::const_iterator i;
        for(typename std::vector<TT>::const_iterator i=m.container.begin();
            i!=m.container.end();
            i++)
          container.push_back(*i);
      }
      ~NodeMap()
      {
        if(G) {
          std::vector<DynMapBase<Node>* >::iterator i;
          for(i=G->dyn_node_maps.begin();
              i!=G->dyn_node_maps.end() && *i!=this; ++i) ;
          //if(*i==this) G->dyn_node_maps.erase(i); //FIXME: Way too slow...
          //A better way to do that: (Is this really important?)
          if(*i==this) {
            *i=G->dyn_node_maps.back();
            G->dyn_node_maps.pop_back();
          }
        }
      }

      void add(const Node k) 
      {
        if(k.n>=int(container.size())) container.resize(k.n+1);
      }

      void erase(const Node) { }
      
      void set(Node n, T a) { container[n.n]=a; }
      //'T& operator[](Node n)' would be wrong here
      typename std::vector<T>::reference
      operator[](Node n) { return container[n.n]; }
      //'const T& operator[](Node n)' would be wrong here
      typename std::vector<T>::const_reference 
      operator[](Node n) const { return container[n.n]; }

      ///\warning There is no safety check at all!
      ///Using operator = between maps attached to different graph may
      ///cause serious problem.
      ///\todo Is this really so?
      ///\todo It can copy between different types.
      const NodeMap<T>& operator=(const NodeMap<T> &m)
      {
        container = m.container;
        return *this;
      }
      template<typename TT>
      const NodeMap<T>& operator=(const NodeMap<TT> &m)
      {
        copy(m.container.begin(), m.container.end(), container.begin());
        return *this;
      }
      
      void update() {}    //Useless for Dynamic Maps
      void update(T a) {}  //Useless for Dynamic Maps
    };
    
    template <typename T> class EdgeMap : public DynMapBase<Edge>
    {
      std::vector<T> container;

    public:
      typedef T ValueType;
      typedef Edge KeyType;

      EdgeMap(const ListGraph &_G) :
        DynMapBase<Edge>(_G), container(_G.maxEdgeId())
      {
        //FIXME: What if there are empty Id's?
        //FIXME: Can I use 'this' in a constructor?
        G->dyn_edge_maps.push_back(this);
      }
      EdgeMap(const ListGraph &_G,const T &t) :
        DynMapBase<Edge>(_G), container(_G.maxEdgeId(),t)
      {
        G->dyn_edge_maps.push_back(this);
      } 
      EdgeMap(const EdgeMap<T> &m) :
        DynMapBase<Edge>(*m.G), container(m.container)
      {
        G->dyn_node_maps.push_back(this);
      }

      template<typename TT> friend class EdgeMap;

      ///\todo It can copy between different types.
      ///
      template<typename TT> EdgeMap(const EdgeMap<TT> &m) :
        DynMapBase<Edge>(*m.G)
      {
        G->dyn_node_maps.push_back(this);
        typename std::vector<TT>::const_iterator i;
        for(typename std::vector<TT>::const_iterator i=m.container.begin();
            i!=m.container.end();
            i++)
          container.push_back(*i);
      }
      ~EdgeMap()
      {
        if(G) {
          std::vector<DynMapBase<Edge>* >::iterator i;
          for(i=G->dyn_edge_maps.begin();
              i!=G->dyn_edge_maps.end() && *i!=this; ++i) ;
          //if(*i==this) G->dyn_edge_maps.erase(i); //Way too slow...
          //A better way to do that: (Is this really important?)
          if(*i==this) {
            *i=G->dyn_edge_maps.back();
            G->dyn_edge_maps.pop_back();
          }
        }
      }
      
      void add(const Edge k) 
      {
        if(k.n>=int(container.size())) container.resize(k.n+1);
      }
      void erase(const Edge) { }
      
      void set(Edge n, T a) { container[n.n]=a; }
      //T get(Edge n) const { return container[n.n]; }
      typename std::vector<T>::reference
      operator[](Edge n) { return container[n.n]; }
      typename std::vector<T>::const_reference
      operator[](Edge n) const { return container[n.n]; }

      ///\warning There is no safety check at all!
      ///Using operator = between maps attached to different graph may
      ///cause serious problem.
      ///\todo Is this really so?
      ///\todo It can copy between different types.
      const EdgeMap<T>& operator=(const EdgeMap<T> &m)
      {
        container = m.container;
        return *this;
      }
      template<typename TT>
      const EdgeMap<T>& operator=(const EdgeMap<TT> &m)
      {
        copy(m.container.begin(), m.container.end(), container.begin());
        return *this;
      }
      
      void update() {}    //Useless for DynMaps
      void update(T a) {}  //Useless for DynMaps
    };

  };

  ///Graph for bidirectional edges.

  ///The purpose of this graph structure is to handle graphs
  ///having bidirectional edges. Here the function \c addEdge(u,v) adds a pair
  ///of oppositely directed edges.
  ///There is a new edge map type called
  ///\ref SymListGraph::SymEdgeMap "SymEdgeMap"
  ///that complements this
  ///feature by
  ///storing shared values for the edge pairs. The usual
  ///\ref GraphSkeleton::EdgeMap "EdgeMap"
  ///can be used
  ///as well.
  ///
  ///The oppositely directed edge can also be obtained easily
  ///using \ref opposite.
  ///
  ///Here erase(Edge) deletes a pair of edges.
  ///
  ///\todo this date structure need some reconsiderations. Maybe it
  ///should be implemented independently from ListGraph.

  class SymListGraph : public ListGraph
  {
  public:
    template<typename T> class SymEdgeMap;
    template<typename T> friend class SymEdgeMap;

    SymListGraph() : ListGraph() { }
    SymListGraph(const ListGraph &_g) : ListGraph(_g) { }
    ///Adds a pair of oppositely directed edges to the graph.
    Edge addEdge(Node u, Node v)
    {
      Edge e = ListGraph::addEdge(u,v);
      ListGraph::addEdge(v,u);
      return e;
    }

    void erase(Node n) { ListGraph::erase(n); }
    ///The oppositely directed edge.

    ///Returns the oppositely directed
    ///pair of the edge \c e.
    Edge opposite(Edge e) const
    {
      Edge f;
      f.idref() = e.idref() - 2*(e.idref()%2) + 1;
      return f;
    }
    
    ///Removes a pair of oppositely directed edges to the graph.
    void erase(Edge e) {
      ListGraph::erase(opposite(e));
      ListGraph::erase(e);
    }
    
    ///Common data storage for the edge pairs.

    ///This map makes it possible to store data shared by the oppositely
    ///directed pairs of edges.
    template <typename T> class SymEdgeMap : public DynMapBase<Edge>
    {
      std::vector<T> container;
      
    public:
      typedef T ValueType;
      typedef Edge KeyType;

      SymEdgeMap(const SymListGraph &_G) :
        DynMapBase<Edge>(_G), container(_G.maxEdgeId()/2)
      {
        static_cast<const SymListGraph*>(G)->dyn_edge_maps.push_back(this);
      }
      SymEdgeMap(const SymListGraph &_G,const T &t) :
        DynMapBase<Edge>(_G), container(_G.maxEdgeId()/2,t)
      {
        G->dyn_edge_maps.push_back(this);
      }

      SymEdgeMap(const SymEdgeMap<T> &m) :
        DynMapBase<SymEdge>(*m.G), container(m.container)
      {
        G->dyn_node_maps.push_back(this);
      }

      //      template<typename TT> friend class SymEdgeMap;

      ///\todo It can copy between different types.
      ///

      template<typename TT> SymEdgeMap(const SymEdgeMap<TT> &m) :
        DynMapBase<SymEdge>(*m.G)
      {
        G->dyn_node_maps.push_back(this);
        typename std::vector<TT>::const_iterator i;
        for(typename std::vector<TT>::const_iterator i=m.container.begin();
            i!=m.container.end();
            i++)
          container.push_back(*i);
      }
 
      ~SymEdgeMap()
      {
        if(G) {
          std::vector<DynMapBase<Edge>* >::iterator i;
          for(i=static_cast<const SymListGraph*>(G)->dyn_edge_maps.begin();
              i!=static_cast<const SymListGraph*>(G)->dyn_edge_maps.end()
                && *i!=this; ++i) ;
          //if(*i==this) G->dyn_edge_maps.erase(i); //Way too slow...
          //A better way to do that: (Is this really important?)
          if(*i==this) {
            *i=static_cast<const SymListGraph*>(G)->dyn_edge_maps.back();
            static_cast<const SymListGraph*>(G)->dyn_edge_maps.pop_back();
          }
        }
      }
      
      void add(const Edge k) 
      {
        if(!k.idref()%2&&k.idref()/2>=int(container.size()))
          container.resize(k.idref()/2+1);
      }
      void erase(const Edge k) { }
      
      void set(Edge n, T a) { container[n.idref()/2]=a; }
      //T get(Edge n) const { return container[n.idref()/2]; }
      typename std::vector<T>::reference
      operator[](Edge n) { return container[n.idref()/2]; }
      typename std::vector<T>::const_reference
      operator[](Edge n) const { return container[n.idref()/2]; }

      ///\warning There is no safety check at all!
      ///Using operator = between maps attached to different graph may
      ///cause serious problem.
      ///\todo Is this really so?
      ///\todo It can copy between different types.
      const SymEdgeMap<T>& operator=(const SymEdgeMap<T> &m)
      {
        container = m.container;
        return *this;
      }
      template<typename TT>
      const SymEdgeMap<T>& operator=(const SymEdgeMap<TT> &m)
      {
        copy(m.container.begin(), m.container.end(), container.begin());
        return *this;
      }
      
      void update() {}    //Useless for DynMaps
      void update(T a) {}  //Useless for DynMaps

    };

  };
  

  ///A graph class containing only nodes.

  ///This class implements a graph structure without edges.
  ///The most useful application of this class is to be the node set of an
  ///\ref EdgeSet class.
  ///
  ///It conforms to the graph interface documented under
  ///the description of \ref GraphSkeleton with the exception that you cannot
  ///add (or delete) edges. The usual edge iterators are exists, but they are
  ///always \ref INVALID.
  ///\sa \ref GraphSkeleton
  ///\se \ref EdgeSet
  class NodeSet {

    //Nodes are double linked.
    //The free nodes are only single linked using the "next" field.
    struct NodeT 
    {
      int first_in,first_out;
      int prev, next;
      //      NodeT() {}
    };

    std::vector<NodeT> nodes;
    //The first node
    int first_node;
    //The first free node
    int first_free_node;
    
  protected:
    
    template <typename Key> class DynMapBase
    {
    protected:
      const NodeSet* G; 
    public:
      virtual void add(const Key k) = NULL;
      virtual void erase(const Key k) = NULL;
      DynMapBase(const NodeSet &_G) : G(&_G) {}
      virtual ~DynMapBase() {}
      friend class NodeSet;
    };
    
  public:
    template <typename T> class EdgeMap;
    template <typename T> class NodeMap;
    
    class Node;
    class Edge;

    //  protected:
    // HELPME:
  protected:
    ///\bug It must be public because of SymEdgeMap.
    ///
    mutable std::vector<DynMapBase<Node> * > dyn_node_maps;
    //mutable std::vector<DynMapBase<Edge> * > dyn_edge_maps;
    
  public:

    class NodeIt;
    class EdgeIt;
    class OutEdgeIt;
    class InEdgeIt;
    
    template <typename T> class NodeMap;
    template <typename T> class EdgeMap;
    
  public:

    ///Default constructor
    NodeSet() : nodes(), first_node(-1),
                  first_free_node(-1) {}
    ///Copy constructor
    NodeSet(const NodeSet &_g) : nodes(_g.nodes), first_node(_g.first_node),
                                     first_free_node(_g.first_free_node) {}
    
    ~NodeSet()
    {
      for(std::vector<DynMapBase<Node> * >::iterator i=dyn_node_maps.begin();
          i!=dyn_node_maps.end(); ++i) (**i).G=NULL;
      //for(std::vector<DynMapBase<Edge> * >::iterator i=dyn_edge_maps.begin();
      //          i!=dyn_edge_maps.end(); ++i) (**i).G=NULL;
    }

    int nodeNum() const { return nodes.size(); }  //FIXME: What is this?
    int edgeNum() const { return 0; }  //FIXME: What is this?

    ///\bug This function does something different than
    ///its name would suggests...
    int maxNodeId() const { return nodes.size(); }  //FIXME: What is this?
    ///\bug This function does something different than
    ///its name would suggests...
    int maxEdgeId() const { return 0; }  //FIXME: What is this?

    Node tail(Edge e) const { return INVALID; }
    Node head(Edge e) const { return INVALID; }

    Node aNode(OutEdgeIt e) const { return INVALID; }
    Node aNode(InEdgeIt e) const { return INVALID; }

    Node bNode(OutEdgeIt e) const { return INVALID; }
    Node bNode(InEdgeIt e) const { return INVALID; }

    NodeIt& first(NodeIt& v) const { 
      v=NodeIt(*this); return v; }
    EdgeIt& first(EdgeIt& e) const { 
      e=EdgeIt(*this); return e; }
    OutEdgeIt& first(OutEdgeIt& e, const Node v) const { 
      e=OutEdgeIt(*this,v); return e; }
    InEdgeIt& first(InEdgeIt& e, const Node v) const { 
      e=InEdgeIt(*this,v); return e; }

//     template< typename It >
//     It first() const { It e; first(e); return e; }

//     template< typename It >
//     It first(Node v) const { It e; first(e,v); return e; }

    bool valid(Edge e) const { return false; }
    bool valid(Node n) const { return n.n!=-1; }
    
    void setInvalid(Edge &e) { }
    void setInvalid(Node &n) { n.n=-1; }
    
    template <typename It> It getNext(It it) const
    { It tmp(it); return next(tmp); }

    NodeIt& next(NodeIt& it) const { 
      it.n=nodes[it.n].next; 
      return it; 
    }
    OutEdgeIt& next(OutEdgeIt& it) const { return it; }
    InEdgeIt& next(InEdgeIt& it) const { return it; }
    EdgeIt& next(EdgeIt& it) const { return it; }

    int id(Node v) const { return v.n; }
    int id(Edge e) const { return -1; }

    /// Adds a new node to the graph.

    /// \todo It adds the nodes in a reversed order.
    /// (i.e. the lastly added node becomes the first.)
    Node addNode() {
      int n;
      
      if(first_free_node==-1)
        {
          n = nodes.size();
          nodes.push_back(NodeT());
        }
      else {
        n = first_free_node;
        first_free_node = nodes[n].next;
      }
      
      nodes[n].next = first_node;
      if(first_node != -1) nodes[first_node].prev = n;
      first_node = n;
      nodes[n].prev = -1;
      
      nodes[n].first_in = nodes[n].first_out = -1;
      
      Node nn; nn.n=n;

      //Update dynamic maps
      for(std::vector<DynMapBase<Node> * >::iterator i=dyn_node_maps.begin();
          i!=dyn_node_maps.end(); ++i) (**i).add(nn);

      return nn;
    }
    
    void erase(Node nn) {
      int n=nn.n;
      
      if(nodes[n].next != -1) nodes[nodes[n].next].prev = nodes[n].prev;
      if(nodes[n].prev != -1) nodes[nodes[n].prev].next = nodes[n].next;
      else first_node = nodes[n].next;
      
      nodes[n].next = first_free_node;
      first_free_node = n;

      //Update dynamic maps
      for(std::vector<DynMapBase<Node> * >::iterator i=dyn_node_maps.begin();
          i!=dyn_node_maps.end(); ++i) (**i).erase(nn);
    }
    
    ///\bug Dynamic maps must be updated!
    ///
    void clear() {
      nodes.clear();
      first_node = first_free_node = -1;
    }

    class Node {
      friend class NodeSet;
      template <typename T> friend class NodeMap;
      
      friend class Edge;
      friend class OutEdgeIt;
      friend class InEdgeIt;

    protected:
      int n;
      friend int NodeSet::id(Node v) const; 
      Node(int nn) {n=nn;}
    public:
      Node() {}
      Node (Invalid i) { n=-1; }
      bool operator==(const Node i) const {return n==i.n;}
      bool operator!=(const Node i) const {return n!=i.n;}
      bool operator<(const Node i) const {return n<i.n;}
    };
    
    class NodeIt : public Node {
      friend class NodeSet;
    public:
      NodeIt(const NodeSet& G) : Node(G.first_node) { }
      NodeIt() : Node() { }
    };

    class Edge {
      //friend class NodeSet;
      //template <typename T> friend class EdgeMap;

      //template <typename T> friend class SymNodeSet::SymEdgeMap;      
      //friend Edge SymNodeSet::opposite(Edge) const;
      
      //      friend class Node;
      //      friend class NodeIt;
    protected:
      //friend int NodeSet::id(Edge e) const;
      //      Edge(int nn) {}
    public:
      Edge() { }
      Edge (Invalid) { }
      bool operator==(const Edge i) const {return true;}
      bool operator!=(const Edge i) const {return false;}
      bool operator<(const Edge i) const {return false;}
      ///\bug This is a workaround until somebody tells me how to
      ///make class \c SymNodeSet::SymEdgeMap friend of Edge
      //      int idref() {return -1;}
      //      int idref() const {return -1;}
    };
    
    class EdgeIt : public Edge {
      //friend class NodeSet;
    public:
      EdgeIt(const NodeSet& G) : Edge() { }
      EdgeIt (Invalid i) : Edge(i) { }
      EdgeIt() : Edge() { }
      ///\bug This is a workaround until somebody tells me how to
      ///make class \c SymNodeSet::SymEdgeMap friend of Edge
      //      int idref() {return -1;}
    };
    
    class OutEdgeIt : public Edge {
      friend class NodeSet;
    public: 
      OutEdgeIt() : Edge() { }
      OutEdgeIt (Invalid i) : Edge(i) { }
      OutEdgeIt(const NodeSet& G,const Node v)  : Edge() {}
    };
    
    class InEdgeIt : public Edge {
      friend class NodeSet;
    public: 
      InEdgeIt() : Edge() { }
      InEdgeIt (Invalid i) : Edge(i) { }
      InEdgeIt(const NodeSet& G,Node v) :Edge() {}
    };

    template <typename T> class NodeMap : public DynMapBase<Node>
    {
      std::vector<T> container;

    public:
      typedef T ValueType;
      typedef Node KeyType;

      NodeMap(const NodeSet &_G) :
        DynMapBase<Node>(_G), container(_G.maxNodeId())
      {
        G->dyn_node_maps.push_back(this);
      }
      NodeMap(const NodeSet &_G,const T &t) :
        DynMapBase<Node>(_G), container(_G.maxNodeId(),t)
      {
        G->dyn_node_maps.push_back(this);
      }
      
      NodeMap(const NodeMap<T> &m) :
        DynMapBase<Node>(*m.G), container(m.container)
      {
        G->dyn_node_maps.push_back(this);
      }

      template<typename TT> friend class NodeMap;
 
      ///\todo It can copy between different types.
      ///
      template<typename TT> NodeMap(const NodeMap<TT> &m) :
        DynMapBase<Node>(*m.G)
      {
        G->dyn_node_maps.push_back(this);
        typename std::vector<TT>::const_iterator i;
        for(typename std::vector<TT>::const_iterator i=m.container.begin();
            i!=m.container.end();
            i++)
          container.push_back(*i);
      }
      ~NodeMap()
      {
        if(G) {
          std::vector<DynMapBase<Node>* >::iterator i;
          for(i=G->dyn_node_maps.begin();
              i!=G->dyn_node_maps.end() && *i!=this; ++i) ;
          //if(*i==this) G->dyn_node_maps.erase(i); //FIXME: Way too slow...
          //A better way to do that: (Is this really important?)
          if(*i==this) {
            *i=G->dyn_node_maps.back();
            G->dyn_node_maps.pop_back();
          }
        }
      }

      void add(const Node k) 
      {
        if(k.n>=int(container.size())) container.resize(k.n+1);
      }

      void erase(const Node) { }
      
      void set(Node n, T a) { container[n.n]=a; }
      //'T& operator[](Node n)' would be wrong here
      typename std::vector<T>::reference
      operator[](Node n) { return container[n.n]; }
      //'const T& operator[](Node n)' would be wrong here
      typename std::vector<T>::const_reference 
      operator[](Node n) const { return container[n.n]; }

      ///\warning There is no safety check at all!
      ///Using operator = between maps attached to different graph may
      ///cause serious problem.
      ///\todo Is this really so?
      ///\todo It can copy between different types.
      const NodeMap<T>& operator=(const NodeMap<T> &m)
      {
        container = m.container;
        return *this;
      }
      template<typename TT>
      const NodeMap<T>& operator=(const NodeMap<TT> &m)
      {
        copy(m.container.begin(), m.container.end(), container.begin());
        return *this;
      }
      
      void update() {}    //Useless for Dynamic Maps
      void update(T a) {}  //Useless for Dynamic Maps
    };
    
    template <typename T> class EdgeMap
    {
    public:
      typedef T ValueType;
      typedef Edge KeyType;

      EdgeMap(const NodeSet &) { }
      EdgeMap(const NodeSet &,const T &) { }
      EdgeMap(const EdgeMap<T> &) { }
      //      template<typename TT> friend class EdgeMap;

      ///\todo It can copy between different types.
      ///
      template<typename TT> EdgeMap(const EdgeMap<TT> &) { }
      ~EdgeMap() { }

      void add(const Edge  ) { }
      void erase(const Edge) { }
      
      void set(Edge, T) { }
      //T get(Edge n) const { return container[n.n]; }
      ValueType &operator[](Edge) { return *((T*)(NULL)); }
      const ValueType &operator[](Edge) const { return *((T*)(NULL)); }

      const EdgeMap<T>& operator=(const EdgeMap<T> &) { return *this; }
    
      template<typename TT>
      const EdgeMap<T>& operator=(const EdgeMap<TT> &m) { return *this; }
      
      void update() {}
      void update(T a) {}
    };
  };



  ///Graph structure using a node set of another graph.

  ///This structure can be used to establish another graph over a node set
  /// of an existing one. The node iterator will go through the nodes of the
  /// original graph, and the NodeMap's of both graphs will convert to
  /// each other.
  ///
  ///\warning Adding or deleting nodes from the graph is not safe if an
  ///\ref EdgeSet is currently attached to it!
  ///
  ///\todo Make it possible to add/delete edges from the base graph
  ///(and from \ref EdgeSet, as well)
  ///
  ///\param GG The type of the graph which shares its node set with this class.
  ///Its interface must conform with \ref GraphSkeleton.
  ///
  ///It conforms to the graph interface documented under
  ///the description of \ref GraphSkeleton.
  ///\sa \ref GraphSkeleton.
  ///\sa \ref NodeSet.
  template<typename GG>
  class EdgeSet {

    typedef GG NodeGraphType;

    NodeGraphType &G;

    class Node;
    
    //Edges are double linked.
    //The free edges are only single linked using the "next_in" field.
    struct NodeT 
    {
      int first_in,first_out;
      NodeT() : first_in(-1), first_out(-1) { }
    };

    struct EdgeT 
    {
      Node head, tail;
      int prev_in, prev_out;
      int next_in, next_out;
    };

    
    typename NodeGraphType::NodeMap<NodeT> nodes;
    
    std::vector<EdgeT> edges;
    //The first free edge
    int first_free_edge;
    
  protected:
    
    template <typename Key> class DynMapBase
    {
    protected:
      const EdgeSet* G; 
    public:
      virtual void add(const Key k) = NULL;
      virtual void erase(const Key k) = NULL;
      DynMapBase(const EdgeSet &_G) : G(&_G) {}
      virtual ~DynMapBase() {}
      friend class EdgeSet;
    };
    
  public:
    //template <typename T> class NodeMap;
    template <typename T> class EdgeMap;
    
    class Node;
    class Edge;

    //  protected:
    // HELPME:
  protected:
    // mutable std::vector<DynMapBase<Node> * > dyn_node_maps;
    ///\bug It must be public because of SymEdgeMap.
    ///
    mutable std::vector<DynMapBase<Edge> * > dyn_edge_maps;
    
  public:

    class NodeIt;
    class EdgeIt;
    class OutEdgeIt;
    class InEdgeIt;
    
    template <typename T> class NodeMap;
    template <typename T> class EdgeMap;
    
  public:

    ///Constructor
    
    ///Construates a new graph based on the nodeset of an existing one.
    ///\param _G the base graph.
    ///\todo It looks like a copy constructor, but it isn't.
    EdgeSet(NodeGraphType &_G) : G(_G),
                                 nodes(_G), edges(),
                                 first_free_edge(-1) { }
    ///Copy constructor

    ///Makes a copy of an EdgeSet.
    ///It will be based on the same graph.
    EdgeSet(const EdgeSet &_g) : G(_g.G), nodes(_g.G), edges(_g.edges),
                                 first_free_edge(_g.first_free_edge) { }
    
    ~EdgeSet()
    {
      // for(std::vector<DynMapBase<Node> * >::iterator i=dyn_node_maps.begin();
      //  i!=dyn_node_maps.end(); ++i) (**i).G=NULL;
      for(typename std::vector<DynMapBase<Edge> * >::iterator
            i=dyn_edge_maps.begin();
          i!=dyn_edge_maps.end(); ++i) (**i).G=NULL;
    }

    int nodeNum() const { return G.nodeNum(); }  //FIXME: What is this?
    int edgeNum() const { return edges.size(); }  //FIXME: What is this?

    ///\bug This function does something different than
    ///its name would suggests...
    int maxNodeId() const { return G.maxNodeId(); }  //FIXME: What is this?
    ///\bug This function does something different than
    ///its name would suggests...
    int maxEdgeId() const { return edges.size(); }  //FIXME: What is this?

    Node tail(Edge e) const { return edges[e.n].tail; }
    Node head(Edge e) const { return edges[e.n].head; }

    Node aNode(OutEdgeIt e) const { return edges[e.n].tail; }
    Node aNode(InEdgeIt e) const { return edges[e.n].head; }

    Node bNode(OutEdgeIt e) const { return edges[e.n].head; }
    Node bNode(InEdgeIt e) const { return edges[e.n].tail; }

    NodeIt& first(NodeIt& v) const { 
      v=NodeIt(*this); return v; }
    EdgeIt& first(EdgeIt& e) const { 
      e=EdgeIt(*this); return e; }
    OutEdgeIt& first(OutEdgeIt& e, const Node v) const { 
      e=OutEdgeIt(*this,v); return e; }
    InEdgeIt& first(InEdgeIt& e, const Node v) const { 
      e=InEdgeIt(*this,v); return e; }

//     template< typename It >
//     It first() const { It e; first(e); return e; }

//     template< typename It >
//     It first(Node v) const { It e; first(e,v); return e; }

    bool valid(Edge e) const { return e.n!=-1; }
    bool valid(Node n) const { return G.valid(n); }
    
    void setInvalid(Edge &e) { e.n=-1; }
    void setInvalid(Node &n) { G.setInvalid(n); }
    
    template <typename It> It getNext(It it) const
    { It tmp(it); return next(tmp); }

    NodeIt& next(NodeIt& it) const { G.next(it); return it; }
    OutEdgeIt& next(OutEdgeIt& it) const
    { it.n=edges[it.n].next_out; return it; }
    InEdgeIt& next(InEdgeIt& it) const
    { it.n=edges[it.n].next_in; return it; }
    EdgeIt& next(EdgeIt& it) const {
      if(edges[it.n].next_in!=-1) { 
        it.n=edges[it.n].next_in;
      }
      else {
        typename NodeGraphType::Node n;
        for(n=G.next(edges[it.n].head);
            G.valid(n) && nodes[n].first_in == -1;
            G.next(n)) ;
        it.n = (G.valid(n))?-1:nodes[n].first_in;
      }
      return it;
    }

    int id(Node v) const { return G.id(v); }
    int id(Edge e) const { return e.n; }

    /// Adds a new node to the graph.
    Node addNode() { return G.AddNode(); }
    
    Edge addEdge(Node u, Node v) {
      int n;
      
      if(first_free_edge==-1)
        {
          n = edges.size();
          edges.push_back(EdgeT());
        }
      else {
        n = first_free_edge;
        first_free_edge = edges[n].next_in;
      }
      
      edges[n].tail = u; edges[n].head = v;

      edges[n].next_out = nodes[u].first_out;
      if(nodes[u].first_out != -1) edges[nodes[u].first_out].prev_out = n;
      edges[n].next_in = nodes[v].first_in;
      if(nodes[v].first_in != -1) edges[nodes[v].first_in].prev_in = n;
      edges[n].prev_in = edges[n].prev_out = -1;
        
      nodes[u].first_out = nodes[v].first_in = n;

      Edge e; e.n=n;

      //Update dynamic maps
      for(typename std::vector<DynMapBase<Edge> * >::iterator
            i=dyn_edge_maps.begin();
          i!=dyn_edge_maps.end(); ++i) (**i).add(e);

      return e;
    }

  private:
    void eraseEdge(int n) {
      
      if(edges[n].next_in!=-1)
        edges[edges[n].next_in].prev_in = edges[n].prev_in;
      if(edges[n].prev_in!=-1)
        edges[edges[n].prev_in].next_in = edges[n].next_in;
      else nodes[edges[n].head].first_in = edges[n].next_in;
      
      if(edges[n].next_out!=-1)
        edges[edges[n].next_out].prev_out = edges[n].prev_out;
      if(edges[n].prev_out!=-1)
        edges[edges[n].prev_out].next_out = edges[n].next_out;
      else nodes[edges[n].tail].first_out = edges[n].next_out;
      
      edges[n].next_in = first_free_edge;
      first_free_edge = -1;      

      //Update dynamic maps
      Edge e; e.n=n;
      for(typename std::vector<DynMapBase<Edge> * >::iterator
            i=dyn_edge_maps.begin();
          i!=dyn_edge_maps.end(); ++i) (**i).erase(e);
    }
      
  public:

//     void erase(Node nn) {
//       int n=nn.n;
//       int m;
//       while((m=nodes[n].first_in)!=-1) eraseEdge(m);
//       while((m=nodes[n].first_out)!=-1) eraseEdge(m);
//     }
    
    void erase(Edge e) { eraseEdge(e.n); }

//     //\bug Dynamic maps must be updated!
//     //
//     void clear() {
//       nodes.clear();edges.clear();
//       first_node=first_free_node=first_free_edge=-1;
//     }

    class Node : public NodeGraphType::Node {
      friend class EdgeSet;
      //      template <typename T> friend class NodeMap;
      
      friend class Edge;
      friend class OutEdgeIt;
      friend class InEdgeIt;
      friend class SymEdge;

    protected:
      friend int EdgeSet::id(Node v) const; 
      //      Node(int nn) {n=nn;}
    public:
      Node() : NodeGraphType::Node() {}
      Node (Invalid i) : NodeGraphType::Node(i) {}
      Node(const typename NodeGraphType::Node &n) : NodeGraphType::Node(n) {}
    };
    
    class NodeIt : public NodeGraphType::NodeIt {
      friend class EdgeSet;
    public:
      NodeIt() : NodeGraphType::NodeIt() { }
      NodeIt (Invalid i) : NodeGraphType::NodeIt(i) {}
      NodeIt(const EdgeSet& _G) : NodeGraphType::NodeIt(_G.G) { }
      NodeIt(const typename NodeGraphType::NodeIt &n)
        : NodeGraphType::NodeIt(n) {}
      operator Node() { return Node(*this);}
    };

    class Edge {
      friend class EdgeSet;
      template <typename T> friend class EdgeMap;

      //template <typename T> friend class SymEdgeSet::SymEdgeMap;      
      //friend Edge SymEdgeSet::opposite(Edge) const;
      
      friend class Node;
      friend class NodeIt;
    protected:
      int n;
      friend int EdgeSet::id(Edge e) const;

      Edge(int nn) {n=nn;}
    public:
      Edge() { }
      Edge (Invalid) { n=-1; }
      bool operator==(const Edge i) const {return n==i.n;}
      bool operator!=(const Edge i) const {return n!=i.n;}
      bool operator<(const Edge i) const {return n<i.n;}
      ///\bug This is a workaround until somebody tells me how to
      ///make class \c SymEdgeSet::SymEdgeMap friend of Edge
      int &idref() {return n;}
      const int &idref() const {return n;}
    };
    
    class EdgeIt : public Edge {
      friend class EdgeSet;
    public:
      EdgeIt(const EdgeSet& G) : Edge() {
        typename NodeGraphType::Node m;
        for(G.first(m);
            G.valid(m) && nodes[m].first_in == -1;  G.next[m]);
        n = G.valid(m)?-1:nodes[m].first_in;
      }
      EdgeIt (Invalid i) : Edge(i) { }
      EdgeIt() : Edge() { }
      ///\bug This is a workaround until somebody tells me how to
      ///make class \c SymEdgeSet::SymEdgeMap friend of Edge
      int &idref() {return n;}
    };
    
    class OutEdgeIt : public Edge {
      friend class EdgeSet;
    public: 
      OutEdgeIt() : Edge() { }
      OutEdgeIt (Invalid i) : Edge(i) { }

      OutEdgeIt(const EdgeSet& G,const Node v) : Edge(nodes[v].first_out) { }
    };
    
    class InEdgeIt : public Edge {
      friend class EdgeSet;
    public: 
      InEdgeIt() : Edge() { }
      InEdgeIt (Invalid i) : Edge(i) { }
      InEdgeIt(const EdgeSet& G,Node v) :Edge(nodes[v].first_in) { }
    };

    template <typename T> class NodeMap : public NodeGraphType::NodeMap<T>
    {
    public:
      NodeMap(const EdgeSet &_G) :
        NodeGraphType::NodeMap<T>(_G.G) { }
      NodeMap(const EdgeSet &_G,const T &t) :
        NodeGraphType::NodeMap<T>(_G.G,t) { }
      //It is unnecessary
      NodeMap(const typename NodeGraphType::NodeMap<T> &m)
        : NodeGraphType::NodeMap<T>(m) { }

      ///\todo It can copy between different types.
      ///
      template<typename TT>
      NodeMap(const typename NodeGraphType::NodeMap<TT> &m)
        : NodeGraphType::NodeMap<T>(m) { }
    };
    
    template <typename T> class EdgeMap : public DynMapBase<Edge>
    {
      std::vector<T> container;

    public:
      typedef T ValueType;
      typedef Edge KeyType;

      EdgeMap(const EdgeSet &_G) :
        DynMapBase<Edge>(_G), container(_G.maxEdgeId())
      {
        //FIXME: What if there are empty Id's?
        //FIXME: Can I use 'this' in a constructor?
        G->dyn_edge_maps.push_back(this);
      }
      EdgeMap(const EdgeSet &_G,const T &t) :
        DynMapBase<Edge>(_G), container(_G.maxEdgeId(),t)
      {
        G->dyn_edge_maps.push_back(this);
      } 
      EdgeMap(const EdgeMap<T> &m) :
        DynMapBase<Edge>(*m.G), container(m.container)
      {
        G->dyn_node_maps.push_back(this);
      }

      template<typename TT> friend class EdgeMap;

      ///\todo It can copy between different types.
      ///
      template<typename TT> EdgeMap(const EdgeMap<TT> &m) :
        DynMapBase<Edge>(*m.G)
      {
        G->dyn_node_maps.push_back(this);
        typename std::vector<TT>::const_iterator i;
        for(typename std::vector<TT>::const_iterator i=m.container.begin();
            i!=m.container.end();
            i++)
          container.push_back(*i);
      }
      ~EdgeMap()
      {
        if(G) {
          typename std::vector<DynMapBase<Edge>* >::iterator i;
          for(i=G->dyn_edge_maps.begin();
              i!=G->dyn_edge_maps.end() && *i!=this; ++i) ;
          //if(*i==this) G->dyn_edge_maps.erase(i); //Way too slow...
          //A better way to do that: (Is this really important?)
          if(*i==this) {
            *i=G->dyn_edge_maps.back();
            G->dyn_edge_maps.pop_back();
          }
        }
      }
      
      void add(const Edge k) 
      {
        if(k.n>=int(container.size())) container.resize(k.n+1);
      }
      void erase(const Edge) { }
      
      void set(Edge n, T a) { container[n.n]=a; }
      //T get(Edge n) const { return container[n.n]; }
      typename std::vector<T>::reference
      operator[](Edge n) { return container[n.n]; }
      typename std::vector<T>::const_reference
      operator[](Edge n) const { return container[n.n]; }

      ///\warning There is no safety check at all!
      ///Using operator = between maps attached to different graph may
      ///cause serious problem.
      ///\todo Is this really so?
      ///\todo It can copy between different types.
      const EdgeMap<T>& operator=(const EdgeMap<T> &m)
      {
        container = m.container;
        return *this;
      }
      template<typename TT>
      const EdgeMap<T>& operator=(const EdgeMap<TT> &m)
      {
        copy(m.container.begin(), m.container.end(), container.begin());
        return *this;
      }
      
      void update() {}    //Useless for DynMaps
      void update(T a) {}  //Useless for DynMaps
    };

  };

/// @}  

} //namespace hugo

#endif //HUGO_LIST_GRAPH_H