/* -*- C++ -*-

 * lemon/graph_adaptor.h - Part of LEMON, a generic C++ optimization library

 *

 * Copyright (C) 2006 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

 * (Egervary Research Group on Combinatorial Optimization, EGRES).

 *

 * Permission to use, modify and distribute this software is granted

 * provided that this copyright notice appears in all copies. For

 * precise terms see the accompanying LICENSE file.

 *

 * This software is provided "AS IS" with no warranty of any kind,

 * express or implied, and with no claim as to its suitability for any

 * purpose.

 *

 */

#ifndef LEMON_GRAPH_ADAPTOR_H

#define LEMON_GRAPH_ADAPTOR_H

///\ingroup graph_adaptors

///\file

///\brief Several graph adaptors.

///

///This file contains several useful graph adaptor functions.

///

///\author Marton Makai

#include <lemon/invalid.h>

#include <lemon/maps.h>

#include <lemon/bits/erasable_graph_extender.h>

#include <lemon/bits/clearable_graph_extender.h>

#include <lemon/bits/extendable_graph_extender.h>

#include <lemon/bits/iterable_graph_extender.h>

#include <lemon/bits/alteration_notifier.h>

#include <lemon/bits/default_map.h>

#include <lemon/bits/graph_extender.h>

#include <iostream>

namespace lemon {

  // Graph adaptors

  /*!

    \addtogroup graph_adaptors

    @{

   */

  /*! 

    Base type for the Graph Adaptors

    \warning Graph adaptors are in even more experimental state than the other

    parts of the lib. Use them at you own risk.

    This is the base type for most of LEMON graph adaptors. 

    This class implements a trivial graph adaptor i.e. it only wraps the 

    functions and types of the graph. The purpose of this class is to 

    make easier implementing graph adaptors. E.g. if an adaptor is 

    considered which differs from the wrapped graph only in some of its 

    functions or types, then it can be derived from GraphAdaptor, and only the 

    differences should be implemented.

    \author Marton Makai 

  */

  template<typename _Graph>

  class GraphAdaptorBase {

  public:

    typedef _Graph Graph;

    typedef Graph ParentGraph;

  protected:

    Graph* graph;

    GraphAdaptorBase() : graph(0) { }

    void setGraph(Graph& _graph) { graph=&_graph; }

  public:

    GraphAdaptorBase(Graph& _graph) : graph(&_graph) { }

    typedef typename Graph::Node Node;

    typedef typename Graph::Edge Edge;

    void first(Node& i) const { graph->first(i); }

    void first(Edge& i) const { graph->first(i); }

    void firstIn(Edge& i, const Node& n) const { graph->firstIn(i, n); }

    void firstOut(Edge& i, const Node& n ) const { graph->firstOut(i, n); }

    void next(Node& i) const { graph->next(i); }

    void next(Edge& i) const { graph->next(i); }

    void nextIn(Edge& i) const { graph->nextIn(i); }

    void nextOut(Edge& i) const { graph->nextOut(i); }

    Node source(const Edge& e) const { return graph->source(e); }

    Node target(const Edge& e) const { return graph->target(e); }

    typedef NodeNumTagIndicator<Graph> NodeNumTag;

    int nodeNum() const { return graph->nodeNum(); }

    typedef EdgeNumTagIndicator<Graph> EdgeNumTag;

    int edgeNum() const { return graph->edgeNum(); }

    typedef FindEdgeTagIndicator<Graph> FindEdgeTag;

    Edge findEdge(const Node& source, const Node& target, 

		  const Edge& prev = INVALID) {

      return graph->findEdge(source, target, prev);

    }

    Node addNode() const { 

      return Node(graph->addNode()); 

    }

    Edge addEdge(const Node& source, const Node& target) const { 

      return Edge(graph->addEdge(source, target)); 

    }

    void erase(const Node& i) const { graph->erase(i); }

    void erase(const Edge& i) const { graph->erase(i); }

    void clear() const { graph->clear(); }

    int id(const Node& v) const { return graph->id(v); }

    int id(const Edge& e) const { return graph->id(e); }

    Edge oppositeNode(const Edge& e) const { 

      return Edge(graph->opposite(e)); 

    }

    template <typename _Value>

    class NodeMap : public _Graph::template NodeMap<_Value> {

    public:

      typedef typename _Graph::template NodeMap<_Value> Parent;

      explicit NodeMap(const GraphAdaptorBase<_Graph>& gw) 

	: Parent(*gw.graph) { }

      NodeMap(const GraphAdaptorBase<_Graph>& gw, const _Value& value)

	: Parent(*gw.graph, value) { }

    };

    template <typename _Value>

    class EdgeMap : public _Graph::template EdgeMap<_Value> {

    public:

      typedef typename _Graph::template EdgeMap<_Value> Parent;

      explicit EdgeMap(const GraphAdaptorBase<_Graph>& gw) 

	: Parent(*gw.graph) { }

      EdgeMap(const GraphAdaptorBase<_Graph>& gw, const _Value& value)

	: Parent(*gw.graph, value) { }

    };

  };

  template <typename _Graph>

  class GraphAdaptor :

    public IterableGraphExtender<GraphAdaptorBase<_Graph> > { 

  public:

    typedef _Graph Graph;

    typedef IterableGraphExtender<GraphAdaptorBase<_Graph> > Parent;

  protected:

    GraphAdaptor() : Parent() { }

  public:

    explicit GraphAdaptor(Graph& _graph) { setGraph(_graph); }

  };

  template <typename _Graph>

  class RevGraphAdaptorBase : public GraphAdaptorBase<_Graph> {

  public:

    typedef _Graph Graph;

    typedef GraphAdaptorBase<_Graph> Parent;

  protected:

    RevGraphAdaptorBase() : Parent() { }

  public:

    typedef typename Parent::Node Node;

    typedef typename Parent::Edge Edge;

    void firstIn(Edge& i, const Node& n) const { Parent::firstOut(i, n); }

    void firstOut(Edge& i, const Node& n ) const { Parent::firstIn(i, n); }

    void nextIn(Edge& i) const { Parent::nextOut(i); }

    void nextOut(Edge& i) const { Parent::nextIn(i); }

    Node source(const Edge& e) const { return Parent::target(e); }

    Node target(const Edge& e) const { return Parent::source(e); }

  };

  /// A graph adaptor which reverses the orientation of the edges.

  ///\warning Graph adaptors are in even more experimental state than the other

  ///parts of the lib. Use them at you own risk.

  ///

  /// Let \f$G=(V, A)\f$ be a directed graph and 

  /// suppose that a graph instange \c g of type 

  /// \c ListGraph implements \f$G\f$.

  /// \code

  /// ListGraph g;

  /// \endcode

  /// For each directed edge 

  /// \f$e\in A\f$, let \f$\bar e\f$ denote the edge obtained by 

  /// reversing its orientation. 

  /// Then RevGraphAdaptor implements the graph structure with node-set 

  /// \f$V\f$ and edge-set 

  /// \f$\{\bar e : e\in A \}\f$, i.e. the graph obtained from \f$G\f$ be 

  /// reversing the orientation of its edges. The following code shows how 

  /// such an instance can be constructed.

  /// \code

  /// RevGraphAdaptor<ListGraph> gw(g);

  /// \endcode

  ///\author Marton Makai

  template<typename _Graph>

  class RevGraphAdaptor : 

    public IterableGraphExtender<RevGraphAdaptorBase<_Graph> > {

  public:

    typedef _Graph Graph;

    typedef IterableGraphExtender<

      RevGraphAdaptorBase<_Graph> > Parent;

  protected:

    RevGraphAdaptor() { }

  public:

    explicit RevGraphAdaptor(_Graph& _graph) { setGraph(_graph); }

  };

  template <typename _Graph, typename NodeFilterMap, 

	    typename EdgeFilterMap, bool checked = true>

  class SubGraphAdaptorBase : public GraphAdaptorBase<_Graph> {

  public:

    typedef _Graph Graph;

    typedef GraphAdaptorBase<_Graph> Parent;

  protected:

    NodeFilterMap* node_filter_map;

    EdgeFilterMap* edge_filter_map;

    SubGraphAdaptorBase() : Parent(), 

			    node_filter_map(0), edge_filter_map(0) { }

    void setNodeFilterMap(NodeFilterMap& _node_filter_map) {

      node_filter_map=&_node_filter_map;

    }

    void setEdgeFilterMap(EdgeFilterMap& _edge_filter_map) {

      edge_filter_map=&_edge_filter_map;

    }

  public:

    typedef typename Parent::Node Node;

    typedef typename Parent::Edge Edge;

    void first(Node& i) const { 

      Parent::first(i); 

      while (i!=INVALID && !(*node_filter_map)[i]) Parent::next(i); 

    }

    void first(Edge& i) const { 

      Parent::first(i); 

      while (i!=INVALID && (!(*edge_filter_map)[i] 

	     || !(*node_filter_map)[Parent::source(i)]

	     || !(*node_filter_map)[Parent::target(i)])) Parent::next(i); 

    }

    void firstIn(Edge& i, const Node& n) const { 

      Parent::firstIn(i, n); 

      while (i!=INVALID && (!(*edge_filter_map)[i] 

	     || !(*node_filter_map)[Parent::source(i)])) Parent::nextIn(i); 

    }

    void firstOut(Edge& i, const Node& n) const { 

      Parent::firstOut(i, n); 

      while (i!=INVALID && (!(*edge_filter_map)[i] 

	     || !(*node_filter_map)[Parent::target(i)])) Parent::nextOut(i); 

    }

    void next(Node& i) const { 

      Parent::next(i); 

      while (i!=INVALID && !(*node_filter_map)[i]) Parent::next(i); 

    }

    void next(Edge& i) const { 

      Parent::next(i); 

      while (i!=INVALID && (!(*edge_filter_map)[i] 

	     || !(*node_filter_map)[Parent::source(i)]

	     || !(*node_filter_map)[Parent::target(i)])) Parent::next(i); 

    }

    void nextIn(Edge& i) const { 

      Parent::nextIn(i); 

      while (i!=INVALID && (!(*edge_filter_map)[i] 

	     || !(*node_filter_map)[Parent::source(i)])) Parent::nextIn(i); 

    }

    void nextOut(Edge& i) const { 

      Parent::nextOut(i); 

      while (i!=INVALID && (!(*edge_filter_map)[i] 

	     || !(*node_filter_map)[Parent::target(i)])) Parent::nextOut(i); 

    }

    /// This function hides \c n in the graph, i.e. the iteration 

    /// jumps over it. This is done by simply setting the value of \c n  

    /// to be false in the corresponding node-map.

    void hide(const Node& n) const { node_filter_map->set(n, false); }

    /// This function hides \c e in the graph, i.e. the iteration 

    /// jumps over it. This is done by simply setting the value of \c e  

    /// to be false in the corresponding edge-map.

    void hide(const Edge& e) const { edge_filter_map->set(e, false); }

    /// The value of \c n is set to be true in the node-map which stores 

    /// hide information. If \c n was hidden previuosly, then it is shown 

    /// again

     void unHide(const Node& n) const { node_filter_map->set(n, true); }

    /// The value of \c e is set to be true in the edge-map which stores 

    /// hide information. If \c e was hidden previuosly, then it is shown 

    /// again

    void unHide(const Edge& e) const { edge_filter_map->set(e, true); }

    /// Returns true if \c n is hidden.

    bool hidden(const Node& n) const { return !(*node_filter_map)[n]; }

    /// Returns true if \c n is hidden.

    bool hidden(const Edge& e) const { return !(*edge_filter_map)[e]; }

    typedef False NodeNumTag;

    typedef False EdgeNumTag;

  };

  template <typename _Graph, typename NodeFilterMap, typename EdgeFilterMap>

  class SubGraphAdaptorBase<_Graph, NodeFilterMap, EdgeFilterMap, false> 

    : public GraphAdaptorBase<_Graph> {

  public:

    typedef _Graph Graph;

    typedef GraphAdaptorBase<_Graph> Parent;

  protected:

    NodeFilterMap* node_filter_map;

    EdgeFilterMap* edge_filter_map;

    SubGraphAdaptorBase() : Parent(), 

			    node_filter_map(0), edge_filter_map(0) { }

    void setNodeFilterMap(NodeFilterMap& _node_filter_map) {

      node_filter_map=&_node_filter_map;

    }

    void setEdgeFilterMap(EdgeFilterMap& _edge_filter_map) {

      edge_filter_map=&_edge_filter_map;

    }

  public:

    typedef typename Parent::Node Node;

    typedef typename Parent::Edge Edge;

    void first(Node& i) const { 

      Parent::first(i); 

      while (i!=INVALID && !(*node_filter_map)[i]) Parent::next(i); 

    }

    void first(Edge& i) const { 

      Parent::first(i); 

      while (i!=INVALID && !(*edge_filter_map)[i]) Parent::next(i); 

    }

    void firstIn(Edge& i, const Node& n) const { 

      Parent::firstIn(i, n); 

      while (i!=INVALID && !(*edge_filter_map)[i]) Parent::nextIn(i); 

    }

    void firstOut(Edge& i, const Node& n) const { 

      Parent::firstOut(i, n); 

      while (i!=INVALID && !(*edge_filter_map)[i]) Parent::nextOut(i); 

    }

    void next(Node& i) const { 

      Parent::next(i); 

      while (i!=INVALID && !(*node_filter_map)[i]) Parent::next(i); 

    }

    void next(Edge& i) const { 

      Parent::next(i); 

      while (i!=INVALID && !(*edge_filter_map)[i]) Parent::next(i); 

    }

    void nextIn(Edge& i) const { 

      Parent::nextIn(i); 

      while (i!=INVALID && !(*edge_filter_map)[i]) Parent::nextIn(i); 

    }

    void nextOut(Edge& i) const { 

      Parent::nextOut(i); 

      while (i!=INVALID && !(*edge_filter_map)[i]) Parent::nextOut(i); 

    }

    /// This function hides \c n in the graph, i.e. the iteration 

    /// jumps over it. This is done by simply setting the value of \c n  

    /// to be false in the corresponding node-map.

    void hide(const Node& n) const { node_filter_map->set(n, false); }

    /// This function hides \c e in the graph, i.e. the iteration 

    /// jumps over it. This is done by simply setting the value of \c e  

    /// to be false in the corresponding edge-map.

    void hide(const Edge& e) const { edge_filter_map->set(e, false); }

    /// The value of \c n is set to be true in the node-map which stores 

    /// hide information. If \c n was hidden previuosly, then it is shown 

    /// again

     void unHide(const Node& n) const { node_filter_map->set(n, true); }

    /// The value of \c e is set to be true in the edge-map which stores 

    /// hide information. If \c e was hidden previuosly, then it is shown 

    /// again

    void unHide(const Edge& e) const { edge_filter_map->set(e, true); }

    /// Returns true if \c n is hidden.

    bool hidden(const Node& n) const { return !(*node_filter_map)[n]; }

    /// Returns true if \c n is hidden.

    bool hidden(const Edge& e) const { return !(*edge_filter_map)[e]; }

    typedef False NodeNumTag;

    typedef False EdgeNumTag;

  };

  /*! \brief A graph adaptor for hiding nodes and edges from a graph.

  \warning Graph adaptors are in even more experimental state than the other

  parts of the lib. Use them at you own risk.

  SubGraphAdaptor shows the graph with filtered node-set and 

  edge-set. If the \c checked parameter is true then it filters the edgeset

  to do not get invalid edges without source or target.

  Let \f$G=(V, A)\f$ be a directed graph 

  and suppose that the graph instance \c g of type ListGraph implements 

  \f$G\f$. 

  Let moreover \f$b_V\f$ and 

  \f$b_A\f$ be bool-valued functions resp. on the node-set and edge-set. 

  SubGraphAdaptor<...>::NodeIt iterates 

  on the node-set \f$\{v\in V : b_V(v)=true\}\f$ and 

  SubGraphAdaptor<...>::EdgeIt iterates 

  on the edge-set \f$\{e\in A : b_A(e)=true\}\f$. Similarly, 

  SubGraphAdaptor<...>::OutEdgeIt and SubGraphAdaptor<...>::InEdgeIt iterates 

  only on edges leaving and entering a specific node which have true value.

  If the \c checked template parameter is false then we have to note that 

  the node-iterator cares only the filter on the node-set, and the 

  edge-iterator cares only the filter on the edge-set. This way the edge-map

  should filter all edges which's source or target is filtered by the 

  node-filter.

  \code

  typedef ListGraph Graph;

  Graph g;

  typedef Graph::Node Node;

  typedef Graph::Edge Edge;

  Node u=g.addNode(); //node of id 0

  Node v=g.addNode(); //node of id 1

  Node e=g.addEdge(u, v); //edge of id 0

  Node f=g.addEdge(v, u); //edge of id 1

  Graph::NodeMap<bool> nm(g, true);

  nm.set(u, false);

  Graph::EdgeMap<bool> em(g, true);

  em.set(e, false);

  typedef SubGraphAdaptor<Graph, Graph::NodeMap<bool>, Graph::EdgeMap<bool> > SubGW;

  SubGW gw(g, nm, em);

  for (SubGW::NodeIt n(gw); n!=INVALID; ++n) std::cout << g.id(n) << std::endl;

  std::cout << ":-)" << std::endl;

  for (SubGW::EdgeIt e(gw); e!=INVALID; ++e) std::cout << g.id(e) << std::endl;

  \endcode

  The output of the above code is the following.

  \code

  1

  :-)

  1

  \endcode

  Note that \c n is of type \c SubGW::NodeIt, but it can be converted to

  \c Graph::Node that is why \c g.id(n) can be applied.

  For other examples see also the documentation of NodeSubGraphAdaptor and 

  EdgeSubGraphAdaptor.

  \author Marton Makai

  */

  template<typename _Graph, typename NodeFilterMap, 

	   typename EdgeFilterMap, bool checked = true>

  class SubGraphAdaptor : 

    public IterableGraphExtender<

    SubGraphAdaptorBase<_Graph, NodeFilterMap, EdgeFilterMap, checked> > {

  public:

    typedef _Graph Graph;

    typedef IterableGraphExtender<

      SubGraphAdaptorBase<_Graph, NodeFilterMap, EdgeFilterMap> > Parent;

  protected:

    SubGraphAdaptor() { }

  public:

    SubGraphAdaptor(_Graph& _graph, NodeFilterMap& _node_filter_map, 

		    EdgeFilterMap& _edge_filter_map) { 

      setGraph(_graph);

      setNodeFilterMap(_node_filter_map);

      setEdgeFilterMap(_edge_filter_map);

    }

  };

  /*! \brief An adaptor for hiding nodes from a graph.

  \warning Graph adaptors are in even more experimental state than the other

  parts of the lib. Use them at you own risk.

  An adaptor for hiding nodes from a graph.

  This adaptor specializes SubGraphAdaptor in the way that only the node-set 

  can be filtered. In usual case the checked parameter is true, we get the

  induced subgraph. But if the checked parameter is false then we can only

  filter only isolated nodes.

  \author Marton Makai

  */

  template<typename Graph, typename NodeFilterMap, bool checked = true>

  class NodeSubGraphAdaptor : 

    public SubGraphAdaptor<Graph, NodeFilterMap, 

			   ConstMap<typename Graph::Edge,bool>, checked> {

  public:

    typedef SubGraphAdaptor<Graph, NodeFilterMap, 

			    ConstMap<typename Graph::Edge,bool> > Parent;

  protected:

    ConstMap<typename Graph::Edge, bool> const_true_map;

  public:

    NodeSubGraphAdaptor(Graph& _graph, NodeFilterMap& _node_filter_map) : 

      Parent(), const_true_map(true) { 

      Parent::setGraph(_graph);

      Parent::setNodeFilterMap(_node_filter_map);

      Parent::setEdgeFilterMap(const_true_map);

    }

  };

  /*! \brief An adaptor for hiding edges from a graph.

  \warning Graph adaptors are in even more experimental state than the other

  parts of the lib. Use them at you own risk.

  An adaptor for hiding edges from a graph.

  This adaptor specializes SubGraphAdaptor in the way that only the edge-set 

  can be filtered. The usefulness of this adaptor is demonstrated in the 

  problem of searching a maximum number of edge-disjoint shortest paths 

  between 

  two nodes \c s and \c t. Shortest here means being shortest w.r.t. 

  non-negative edge-lengths. Note that 

  the comprehension of the presented solution 

  need's some elementary knowledge from combinatorial optimization. 

  If a single shortest path is to be 

  searched between \c s and \c t, then this can be done easily by 

  applying the Dijkstra algorithm. What happens, if a maximum number of 

  edge-disjoint shortest paths is to be computed. It can be proved that an 

  edge can be in a shortest path if and only if it is tight with respect to 

  the potential function computed by Dijkstra. Moreover, any path containing 

  only such edges is a shortest one. Thus we have to compute a maximum number 

  of edge-disjoint paths between \c s and \c t in the graph which has edge-set 

  all the tight edges. The computation will be demonstrated on the following 

  graph, which is read from the dimacs file \c sub_graph_adaptor_demo.dim. 

  The full source code is available in \ref sub_graph_adaptor_demo.cc. 

  If you are interested in more demo programs, you can use 

  \ref dim_to_dot.cc to generate .dot files from dimacs files. 

  The .dot file of the following figure was generated by  

  the demo program \ref dim_to_dot.cc.

  \dot

  digraph lemon_dot_example {

  node [ shape=ellipse, fontname=Helvetica, fontsize=10 ];

  n0 [ label="0 (s)" ];

  n1 [ label="1" ];

  n2 [ label="2" ];

  n3 [ label="3" ];

  n4 [ label="4" ];

  n5 [ label="5" ];

  n6 [ label="6 (t)" ];

  edge [ shape=ellipse, fontname=Helvetica, fontsize=10 ];

  n5 ->  n6 [ label="9, length:4" ];

  n4 ->  n6 [ label="8, length:2" ];

  n3 ->  n5 [ label="7, length:1" ];

  n2 ->  n5 [ label="6, length:3" ];

  n2 ->  n6 [ label="5, length:5" ];

  n2 ->  n4 [ label="4, length:2" ];

  n1 ->  n4 [ label="3, length:3" ];

  n0 ->  n3 [ label="2, length:1" ];

  n0 ->  n2 [ label="1, length:2" ];

  n0 ->  n1 [ label="0, length:3" ];

  }

  \enddot

  \code

  Graph g;

  Node s, t;

  LengthMap length(g);

  readDimacs(std::cin, g, length, s, t);

  cout << "edges with lengths (of form id, source--length->target): " << endl;

  for(EdgeIt e(g); e!=INVALID; ++e) 

    cout << g.id(e) << ", " << g.id(g.source(e)) << "--" 

         << length[e] << "->" << g.id(g.target(e)) << endl;

  cout << "s: " << g.id(s) << " t: " << g.id(t) << endl;

  \endcode

  Next, the potential function is computed with Dijkstra.

  \code

  typedef Dijkstra<Graph, LengthMap> Dijkstra;

  Dijkstra dijkstra(g, length);

  dijkstra.run(s);

  \endcode

  Next, we consrtruct a map which filters the edge-set to the tight edges.

  \code

  typedef TightEdgeFilterMap<Graph, const Dijkstra::DistMap, LengthMap> 

    TightEdgeFilter;

  TightEdgeFilter tight_edge_filter(g, dijkstra.distMap(), length);

  typedef EdgeSubGraphAdaptor<Graph, TightEdgeFilter> SubGW;

  SubGW gw(g, tight_edge_filter);

  \endcode

  Then, the maximum nimber of edge-disjoint \c s-\c t paths are computed 

  with a max flow algorithm Preflow.

  \code

  ConstMap<Edge, int> const_1_map(1);

  Graph::EdgeMap<int> flow(g, 0);

  Preflow<SubGW, int, ConstMap<Edge, int>, Graph::EdgeMap<int> > 

    preflow(gw, s, t, const_1_map, flow);

  preflow.run();

  \endcode

  Last, the output is:

  \code  

  cout << "maximum number of edge-disjoint shortest path: " 

       << preflow.flowValue() << endl;

  cout << "edges of the maximum number of edge-disjoint shortest s-t paths: " 

       << endl;

  for(EdgeIt e(g); e!=INVALID; ++e) 

    if (flow[e])

      cout << " " << g.id(g.source(e)) << "--" 

	   << length[e] << "->" << g.id(g.target(e)) << endl;

  \endcode

  The program has the following (expected :-)) output:

  \code

  edges with lengths (of form id, source--length->target):

   9, 5--4->6

   8, 4--2->6

   7, 3--1->5

   6, 2--3->5

   5, 2--5->6

   4, 2--2->4

   3, 1--3->4

   2, 0--1->3

   1, 0--2->2

   0, 0--3->1

  s: 0 t: 6

  maximum number of edge-disjoint shortest path: 2

  edges of the maximum number of edge-disjoint shortest s-t paths:

   9, 5--4->6

   8, 4--2->6

   7, 3--1->5

   4, 2--2->4

   2, 0--1->3

   1, 0--2->2

  \endcode

  \author Marton Makai

  */

  template<typename Graph, typename EdgeFilterMap>

  class EdgeSubGraphAdaptor : 

    public SubGraphAdaptor<Graph, ConstMap<typename Graph::Node,bool>, 

			   EdgeFilterMap, false> {

  public:

    typedef SubGraphAdaptor<Graph, ConstMap<typename Graph::Node,bool>, 

			    EdgeFilterMap, false> Parent;

  protected:

    ConstMap<typename Graph::Node, bool> const_true_map;

  public:

    EdgeSubGraphAdaptor(Graph& _graph, EdgeFilterMap& _edge_filter_map) : 

      Parent(), const_true_map(true) { 

      Parent::setGraph(_graph);

      Parent::setNodeFilterMap(const_true_map);

      Parent::setEdgeFilterMap(_edge_filter_map);

    }

  };

  template <typename _Graph>

  class UndirGraphAdaptorBase : 

    public UndirGraphExtender<GraphAdaptorBase<_Graph> > {

  public:

    typedef _Graph Graph;

    typedef UndirGraphExtender<GraphAdaptorBase<_Graph> > Parent;

  protected:

    UndirGraphAdaptorBase() : Parent() { }

  public:

    typedef typename Parent::UndirEdge UndirEdge;

    typedef typename Parent::Edge Edge;

    template <typename T>

    class EdgeMap {

    protected:

      const UndirGraphAdaptorBase<_Graph>* g;

      template <typename TT> friend class EdgeMap;

      typename _Graph::template EdgeMap<T> forward_map, backward_map; 

    public:

      typedef T Value;

      typedef Edge Key;

      EdgeMap(const UndirGraphAdaptorBase<_Graph>& _g) : g(&_g), 

	forward_map(*(g->graph)), backward_map(*(g->graph)) { }

      EdgeMap(const UndirGraphAdaptorBase<_Graph>& _g, T a) : g(&_g), 

	forward_map(*(g->graph), a), backward_map(*(g->graph), a) { }

      void set(Edge e, T a) { 

	if (g->direction(e)) 

	  forward_map.set(e, a); 

	else 

	  backward_map.set(e, a); 

      }

      T operator[](Edge e) const { 

	if (g->direction(e)) 

	  return forward_map[e]; 

	else 

	  return backward_map[e]; 

      }

    };

    template <typename T>

    class UndirEdgeMap {

      template <typename TT> friend class UndirEdgeMap;

      typename _Graph::template EdgeMap<T> map; 

    public:

      typedef T Value;

      typedef UndirEdge Key;

      UndirEdgeMap(const UndirGraphAdaptorBase<_Graph>& g) : 

	map(*(g.graph)) { }

      UndirEdgeMap(const UndirGraphAdaptorBase<_Graph>& g, T a) : 

	map(*(g.graph), a) { }

      void set(UndirEdge e, T a) { 

	map.set(e, a); 

      }

      T operator[](UndirEdge e) const { 

	return map[e]; 

      }

    };

  };

  /// \brief An undirected graph is made from a directed graph by an adaptor

  ///

  /// Undocumented, untested!!!

  /// If somebody knows nice demo application, let's polulate it.

  /// 

  /// \author Marton Makai

  template<typename _Graph>

  class UndirGraphAdaptor : 

    public IterableUndirGraphExtender<

    UndirGraphAdaptorBase<_Graph> > {

  public:

    typedef _Graph Graph;

    typedef IterableUndirGraphExtender<

      UndirGraphAdaptorBase<_Graph> > Parent;

  protected:

    UndirGraphAdaptor() { }

  public:

    UndirGraphAdaptor(_Graph& _graph) { 

      setGraph(_graph);

    }

  };

  template <typename _Graph, 

	    typename ForwardFilterMap, typename BackwardFilterMap>

  class SubBidirGraphAdaptorBase : public GraphAdaptorBase<_Graph> {

  public:

    typedef _Graph Graph;

    typedef GraphAdaptorBase<_Graph> Parent;

  protected:

    ForwardFilterMap* forward_filter;

    BackwardFilterMap* backward_filter;

    SubBidirGraphAdaptorBase() : Parent(), 

				 forward_filter(0), backward_filter(0) { }

    void setForwardFilterMap(ForwardFilterMap& _forward_filter) {

      forward_filter=&_forward_filter;

    }

    void setBackwardFilterMap(BackwardFilterMap& _backward_filter) {

      backward_filter=&_backward_filter;

    }

  public:

//     SubGraphAdaptorBase(Graph& _graph, 

// 			NodeFilterMap& _node_filter_map, 

// 			EdgeFilterMap& _edge_filter_map) : 

//       Parent(&_graph), 

//       node_filter_map(&node_filter_map), 

//       edge_filter_map(&edge_filter_map) { }

    typedef typename Parent::Node Node;

    typedef typename _Graph::Edge GraphEdge;

    template <typename T> class EdgeMap;

    /// SubBidirGraphAdaptorBase<..., ..., ...>::Edge is inherited from 

    /// _Graph::Edge. It contains an extra bool flag which is true 

    /// if and only if the 

    /// edge is the backward version of the original edge.

    class Edge : public _Graph::Edge {

      friend class SubBidirGraphAdaptorBase<

	Graph, ForwardFilterMap, BackwardFilterMap>;

      template<typename T> friend class EdgeMap;

    protected:

      bool backward; //true, iff backward

    public:

      Edge() { }

      /// \todo =false is needed, or causes problems?

      /// If \c _backward is false, then we get an edge corresponding to the 

      /// original one, otherwise its oppositely directed pair is obtained.

      Edge(const typename _Graph::Edge& e, bool _backward/*=false*/) : 

	_Graph::Edge(e), backward(_backward) { }

      Edge(Invalid i) : _Graph::Edge(i), backward(true) { }

      bool operator==(const Edge& v) const { 

	return (this->backward==v.backward && 

		static_cast<typename _Graph::Edge>(*this)==

		static_cast<typename _Graph::Edge>(v));

      } 

      bool operator!=(const Edge& v) const { 

	return (this->backward!=v.backward || 

		static_cast<typename _Graph::Edge>(*this)!=

		static_cast<typename _Graph::Edge>(v));

      }

    };

    void first(Node& i) const { 

      Parent::first(i); 

    }

    void first(Edge& i) const { 

      Parent::first(i); 

      i.backward=false;

      while (*static_cast<GraphEdge*>(&i)!=INVALID && 

	     !(*forward_filter)[i]) Parent::next(i);

      if (*static_cast<GraphEdge*>(&i)==INVALID) {

	Parent::first(i); 

	i.backward=true;

	while (*static_cast<GraphEdge*>(&i)!=INVALID && 

	       !(*backward_filter)[i]) Parent::next(i);

      }

    }

    void firstIn(Edge& i, const Node& n) const { 

      Parent::firstIn(i, n); 

      i.backward=false;

      while (*static_cast<GraphEdge*>(&i)!=INVALID && 

	     !(*forward_filter)[i]) Parent::nextIn(i);

      if (*static_cast<GraphEdge*>(&i)==INVALID) {

	Parent::firstOut(i, n); 

	i.backward=true;

	while (*static_cast<GraphEdge*>(&i)!=INVALID && 

	       !(*backward_filter)[i]) Parent::nextOut(i);

      }

    }

    void firstOut(Edge& i, const Node& n) const { 

      Parent::firstOut(i, n); 

      i.backward=false;

      while (*static_cast<GraphEdge*>(&i)!=INVALID && 

	     !(*forward_filter)[i]) Parent::nextOut(i);

      if (*static_cast<GraphEdge*>(&i)==INVALID) {

	Parent::firstIn(i, n); 

	i.backward=true;

	while (*static_cast<GraphEdge*>(&i)!=INVALID && 

	       !(*backward_filter)[i]) Parent::nextIn(i);

      }

    }

    void next(Node& i) const { 

      Parent::next(i); 

    }

    void next(Edge& i) const { 

      if (!(i.backward)) {

	Parent::next(i);

	while (*static_cast<GraphEdge*>(&i)!=INVALID && 

	       !(*forward_filter)[i]) Parent::next(i);

	if (*static_cast<GraphEdge*>(&i)==INVALID) {

	  Parent::first(i); 

	  i.backward=true;

	  while (*static_cast<GraphEdge*>(&i)!=INVALID && 

		 !(*backward_filter)[i]) Parent::next(i);

	}

      } else {

	Parent::next(i);

	while (*static_cast<GraphEdge*>(&i)!=INVALID && 

	       !(*backward_filter)[i]) Parent::next(i);

      }

    }

    void nextIn(Edge& i) const { 

      if (!(i.backward)) {

	Node n=Parent::target(i);

	Parent::nextIn(i);

	while (*static_cast<GraphEdge*>(&i)!=INVALID && 

	       !(*forward_filter)[i]) Parent::nextIn(i);

	if (*static_cast<GraphEdge*>(&i)==INVALID) {

	  Parent::firstOut(i, n); 

	  i.backward=true;

	  while (*static_cast<GraphEdge*>(&i)!=INVALID && 

		 !(*backward_filter)[i]) Parent::nextOut(i);

	}

      } else {

	Parent::nextOut(i);

	while (*static_cast<GraphEdge*>(&i)!=INVALID && 

	       !(*backward_filter)[i]) Parent::nextOut(i);

      }

    }

    void nextOut(Edge& i) const { 

      if (!(i.backward)) {

	Node n=Parent::source(i);

	Parent::nextOut(i);

	while (*static_cast<GraphEdge*>(&i)!=INVALID && 

	       !(*forward_filter)[i]) Parent::nextOut(i);

	if (*static_cast<GraphEdge*>(&i)==INVALID) {

	  Parent::firstIn(i, n); 

	  i.backward=true;

	  while (*static_cast<GraphEdge*>(&i)!=INVALID && 

		 !(*backward_filter)[i]) Parent::nextIn(i);

	}

      } else {

	Parent::nextIn(i);

	while (*static_cast<GraphEdge*>(&i)!=INVALID && 

	       !(*backward_filter)[i]) Parent::nextIn(i);

      }

    }

    Node source(Edge e) const { 

      return ((!e.backward) ? this->graph->source(e) : this->graph->target(e)); }

    Node target(Edge e) const { 

      return ((!e.backward) ? this->graph->target(e) : this->graph->source(e)); }

    /// Gives back the opposite edge.

    Edge opposite(const Edge& e) const { 

      Edge f=e;

      f.backward=!f.backward;

      return f;

    }

    /// \warning This is a linear time operation and works only if 

    /// \c Graph::EdgeIt is defined.

    /// \todo hmm

    int edgeNum() const { 

      int i=0;

      Edge e;

      for (first(e); e!=INVALID; next(e)) ++i;

      return i; 

    }

    bool forward(const Edge& e) const { return !e.backward; }

    bool backward(const Edge& e) const { return e.backward; }

    template <typename T>

    /// \c SubBidirGraphAdaptorBase<..., ..., ...>::EdgeMap contains two 

    /// _Graph::EdgeMap one for the forward edges and 

    /// one for the backward edges.

    class EdgeMap {

      template <typename TT> friend class EdgeMap;

      typename _Graph::template EdgeMap<T> forward_map, backward_map; 

    public:

      typedef T Value;

      typedef Edge Key;

      EdgeMap(const SubBidirGraphAdaptorBase<_Graph, 

	      ForwardFilterMap, BackwardFilterMap>& g) : 

	forward_map(*(g.graph)), backward_map(*(g.graph)) { }

      EdgeMap(const SubBidirGraphAdaptorBase<_Graph, 

	      ForwardFilterMap, BackwardFilterMap>& g, T a) : 

	forward_map(*(g.graph), a), backward_map(*(g.graph), a) { }

      void set(Edge e, T a) { 

	if (!e.backward) 

	  forward_map.set(e, a); 

	else 

	  backward_map.set(e, a); 

      }

//       typename _Graph::template EdgeMap<T>::ConstReference 

//       operator[](Edge e) const { 

// 	if (!e.backward) 

// 	  return forward_map[e]; 

// 	else 

// 	  return backward_map[e]; 

//       }

//      typename _Graph::template EdgeMap<T>::Reference 

      T operator[](Edge e) const { 

	if (!e.backward) 

	  return forward_map[e]; 

	else 

	  return backward_map[e]; 

      }