NodeRefMap& nodeRefMap, EdgeRefMap& edgeRefMap) {

         to.build(from, nodeRefMap, edgeRefMap);

       }

     };

     template <typename BpGraph, typename Enable = void>

     struct BpGraphCopySelector {

       template <typename From, typename NodeRefMap, typename EdgeRefMap>

       static void copy(const From& from, BpGraph &to,

                        NodeRefMap& nodeRefMap, EdgeRefMap& edgeRefMap) {

         to.clear();

         for (typename From::RedIt it(from); it != INVALID; ++it) {

           nodeRefMap[it] = to.addRedNode();

         }

         for (typename From::BlueIt it(from); it != INVALID; ++it) {

           nodeRefMap[it] = to.addBlueNode();

         }

         for (typename From::EdgeIt it(from); it != INVALID; ++it) {

           edgeRefMap[it] = to.addEdge(nodeRefMap[from.redNode(it)],

                                       nodeRefMap[from.blueNode(it)]);

         }

       }

     };

     template <typename BpGraph>

     struct BpGraphCopySelector<

       BpGraph,

       typename enable_if<typename BpGraph::BuildTag, void>::type>

     {

       template <typename From, typename NodeRefMap, typename EdgeRefMap>

       static void copy(const From& from, BpGraph &to,

   }

   /// \brief Class to copy a bipartite graph.

   ///

   /// Class to copy a bipartite graph to another graph (duplicate a

   /// graph). The simplest way of using it is through the

   /// \c bpGraphCopy() function.

   ///

   /// This class not only make a copy of a bipartite graph, but it can

   /// create references and cross references between the nodes, edges

   /// and arcs of the two graphs, and it can copy maps for using with

   /// the newly created graph.

   ///

   /// To make a copy from a graph, first an instance of BpGraphCopy

   /// should be created, then the data belongs to the graph should

   /// assigned to copy. In the end, the \c run() member should be

   /// called.

   ///

   /// The next code copies a graph with several data:

   ///\code

   ///  BpGraphCopy<OrigBpGraph, NewBpGraph> cg(orig_graph, new_graph);

   ///  // Create references for the nodes

   ///  OrigBpGraph::NodeMap<NewBpGraph::Node> nr(orig_graph);

   ///  cg.nodeRef(nr);

   ///  // Create cross references (inverse) for the edges

   ///  NewBpGraph::EdgeMap<OrigBpGraph::Edge> ecr(new_graph);

   ///  cg.edgeCrossRef(ecr);

   ///  // Copy a red map

   ///  OrigBpGraph::RedMap<double> ormap(orig_graph);

   ///  NewBpGraph::RedMap<double> nrmap(new_graph);

   ///  cg.edgeMap(ormap, nrmap);

   ///  // Copy a node

   ///  OrigBpGraph::Node on;

   ///  NewBpGraph::Node nn;

   ///  cg.node(on, nn);

   ///  // Execute copying

   ///  cg.run();

   ///\endcode

   template <typename From, typename To>

   class BpGraphCopy {

   private:

     typedef typename From::Node Node;

     typedef typename From::RedNode RedNode;

     typedef typename From::BlueNode BlueNode;

     typedef typename From::NodeIt NodeIt;

     typedef typename From::Arc Arc;

     typedef typename From::ArcIt ArcIt;

     typedef typename From::Edge Edge;

     typedef typename From::EdgeIt EdgeIt;

     typedef typename To::Node TNode;

     typedef typename To::Arc TArc;

     typedef typename To::Edge TEdge;

     typedef typename From::template NodeMap<TNode> NodeRefMap;

     typedef typename From::template EdgeMap<TEdge> EdgeRefMap;

     struct ArcRefMap {

       ArcRefMap(const From& from, const To& to, const EdgeRefMap& edge_ref)

         : _from(from), _to(to), _edge_ref(edge_ref) {}

       typedef typename From::Arc Key;

       typedef typename To::Arc Value;

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

         return _to.direct(_edge_ref[key], _from.direction(key));

       }

       const From& _from;

       const To& _to;

       const EdgeRefMap& _edge_ref;

     };

   public:

     /// \brief Constructor of BpGraphCopy.

     ///

     /// Constructor of BpGraphCopy for copying the content of the

     /// \c from graph into the \c to graph.

     BpGraphCopy(const From& from, To& to)

       : _from(from), _to(to) {}

     /// \brief Destructor of BpGraphCopy

     ///

     /// Destructor of BpGraphCopy.

     ~BpGraphCopy() {

       for (int i = 0; i < int(_node_maps.size()); ++i) {

         delete _node_maps[i];

       }

       for (int i = 0; i < int(_red_maps.size()); ++i) {

         delete _red_maps[i];

       }

       for (int i = 0; i < int(_blue_maps.size()); ++i) {

         delete _blue_maps[i];

       }

       for (int i = 0; i < int(_arc_maps.size()); ++i) {

         delete _arc_maps[i];

       }

       for (int i = 0; i < int(_edge_maps.size()); ++i) {

         delete _edge_maps[i];

       }

     }

     /// \brief Copy the node references into the given map.

     ///

     /// This function copies the node references into the given map.

     /// The parameter should be a map, whose key type is the Node type of

     /// the source graph, while the value type is the Node type of the

     /// destination graph.

     template <typename NodeRef>

     BpGraphCopy& nodeRef(NodeRef& map) {

       _node_maps.push_back(new _core_bits::RefCopy<From, Node,

                            NodeRefMap, NodeRef>(map));

       return *this;

     }

     /// \brief Copy the node cross references into the given map.

     ///

     /// This function copies the node cross references (reverse references)

     /// into the given map. The parameter should be a map, whose key type

     /// is the Node type of the destination graph, while the value type is

     /// the Node type of the source graph.

     template <typename NodeCrossRef>

     BpGraphCopy& nodeCrossRef(NodeCrossRef& map) {

       _node_maps.push_back(new _core_bits::CrossRefCopy<From, Node,

                            NodeRefMap, NodeCrossRef>(map));

       return *this;

     }

     /// \brief Make a copy of the given node map.

     ///

     /// This function makes a copy of the given node map for the newly

     /// created graph.

     /// The key type of the new map \c tmap should be the Node type of the

     /// destination graph, and the key type of the original map \c map

     /// should be the Node type of the source graph.

     template <typename FromMap, typename ToMap>

     BpGraphCopy& nodeMap(const FromMap& map, ToMap& tmap) {

       _node_maps.push_back(new _core_bits::MapCopy<From, Node,

                            NodeRefMap, FromMap, ToMap>(map, tmap));

       return *this;

     }

     /// \brief Make a copy of the given node.

     ///

     /// This function makes a copy of the given node.

     BpGraphCopy& node(const Node& node, TNode& tnode) {

       _node_maps.push_back(new _core_bits::ItemCopy<From, Node,

                            NodeRefMap, TNode>(node, tnode));

       return *this;

     }

     /// \brief Copy the red node references into the given map.

     ///

     /// This function copies the red node references into the given

     /// map.  The parameter should be a map, whose key type is the

     /// Node type of the source graph with the red item set, while the

     /// value type is the Node type of the destination graph.

     template <typename RedRef>

     BpGraphCopy& redRef(RedRef& map) {

       _red_maps.push_back(new _core_bits::RefCopy<From, RedNode,

                           NodeRefMap, RedRef>(map));

       return *this;

     }

     /// \brief Copy the red node cross references into the given map.

     ///

     /// This function copies the red node cross references (reverse

     /// references) into the given map. The parameter should be a map,

     /// whose key type is the Node type of the destination graph with

     /// the red item set, while the value type is the Node type of the

     /// source graph.

     template <typename RedCrossRef>

     BpGraphCopy& redCrossRef(RedCrossRef& map) {

       _red_maps.push_back(new _core_bits::CrossRefCopy<From, RedNode,

                           NodeRefMap, RedCrossRef>(map));

       return *this;

     }

     /// \brief Make a copy of the given red node map.

     ///

     /// This function makes a copy of the given red node map for the newly

     /// created graph.

     /// The key type of the new map \c tmap should be the Node type of

     /// the destination graph with the red items, and the key type of

     /// the original map \c map should be the Node type of the source

     /// graph.

     template <typename FromMap, typename ToMap>

     BpGraphCopy& redMap(const FromMap& map, ToMap& tmap) {

       _red_maps.push_back(new _core_bits::MapCopy<From, RedNode,

                            NodeRefMap, FromMap, ToMap>(map, tmap));

       return *this;

     }

     /// \brief Copy the blue node references into the given map.

     ///

     /// This function copies the blue node references into the given

     /// map.  The parameter should be a map, whose key type is the

     /// Node type of the source graph with the blue item set, while the

     /// value type is the Node type of the destination graph.

     template <typename BlueRef>

     BpGraphCopy& blueRef(BlueRef& map) {

       _blue_maps.push_back(new _core_bits::RefCopy<From, BlueNode,

                            NodeRefMap, BlueRef>(map));

       return *this;

     }

     /// \brief Copy the blue node cross references into the given map.

     ///

     /// This function copies the blue node cross references (reverse

     /// references) into the given map. The parameter should be a map,

     /// whose key type is the Node type of the destination graph with

     /// the blue item set, while the value type is the Node type of the

     /// source graph.

     template <typename BlueCrossRef>

     BpGraphCopy& blueCrossRef(BlueCrossRef& map) {

       _blue_maps.push_back(new _core_bits::CrossRefCopy<From, BlueNode,

                            NodeRefMap, BlueCrossRef>(map));

       return *this;

     }

     /// \brief Make a copy of the given blue node map.

     ///

     /// This function makes a copy of the given blue node map for the newly

     /// created graph.

     /// The key type of the new map \c tmap should be the Node type of

     /// the destination graph with the blue items, and the key type of

     /// the original map \c map should be the Node type of the source

     /// graph.

     template <typename FromMap, typename ToMap>

     BpGraphCopy& blueMap(const FromMap& map, ToMap& tmap) {

       _blue_maps.push_back(new _core_bits::MapCopy<From, BlueNode,

                            NodeRefMap, FromMap, ToMap>(map, tmap));

       return *this;

     }

     /// \brief Copy the arc references into the given map.

     ///

     /// This function copies the arc references into the given map.

     /// The parameter should be a map, whose key type is the Arc type of

     /// the source graph, while the value type is the Arc type of the

     /// destination graph.

     template <typename ArcRef>

     BpGraphCopy& arcRef(ArcRef& map) {

       _arc_maps.push_back(new _core_bits::RefCopy<From, Arc,

                           ArcRefMap, ArcRef>(map));

       return *this;

     }

     /// \brief Copy the arc cross references into the given map.

     ///

     /// This function copies the arc cross references (reverse references)

     /// into the given map. The parameter should be a map, whose key type

     /// is the Arc type of the destination graph, while the value type is

     /// the Arc type of the source graph.

     template <typename ArcCrossRef>

     BpGraphCopy& arcCrossRef(ArcCrossRef& map) {

       _arc_maps.push_back(new _core_bits::CrossRefCopy<From, Arc,

                           ArcRefMap, ArcCrossRef>(map));

       return *this;

     }

     /// \brief Make a copy of the given arc map.

     ///

     /// This function makes a copy of the given arc map for the newly

     /// created graph.

     /// The key type of the new map \c tmap should be the Arc type of the

     /// destination graph, and the key type of the original map \c map

     /// should be the Arc type of the source graph.

     template <typename FromMap, typename ToMap>

     BpGraphCopy& arcMap(const FromMap& map, ToMap& tmap) {

       _arc_maps.push_back(new _core_bits::MapCopy<From, Arc,

                           ArcRefMap, FromMap, ToMap>(map, tmap));

       return *this;

     }

     /// \brief Make a copy of the given arc.

     ///

     /// This function makes a copy of the given arc.

     BpGraphCopy& arc(const Arc& arc, TArc& tarc) {

       _arc_maps.push_back(new _core_bits::ItemCopy<From, Arc,

                           ArcRefMap, TArc>(arc, tarc));

       return *this;

     }

     /// \brief Copy the edge references into the given map.

     ///

     /// This function copies the edge references into the given map.

     /// The parameter should be a map, whose key type is the Edge type of

     /// the source graph, while the value type is the Edge type of the

     /// destination graph.

     template <typename EdgeRef>

     BpGraphCopy& edgeRef(EdgeRef& map) {

       _edge_maps.push_back(new _core_bits::RefCopy<From, Edge,

                            EdgeRefMap, EdgeRef>(map));

       return *this;

     }

     /// \brief Copy the edge cross references into the given map.

     ///

     /// This function copies the edge cross references (reverse references)

     /// into the given map. The parameter should be a map, whose key type

     /// is the Edge type of the destination graph, while the value type is

     /// the Edge type of the source graph.

     template <typename EdgeCrossRef>

     BpGraphCopy& edgeCrossRef(EdgeCrossRef& map) {

       _edge_maps.push_back(new _core_bits::CrossRefCopy<From,

                            Edge, EdgeRefMap, EdgeCrossRef>(map));

       return *this;

     }

     /// \brief Make a copy of the given edge map.

     ///

     /// This function makes a copy of the given edge map for the newly

     /// created graph.

     /// The key type of the new map \c tmap should be the Edge type of the

     /// destination graph, and the key type of the original map \c map

     /// should be the Edge type of the source graph.

     template <typename FromMap, typename ToMap>

     BpGraphCopy& edgeMap(const FromMap& map, ToMap& tmap) {

       _edge_maps.push_back(new _core_bits::MapCopy<From, Edge,

                            EdgeRefMap, FromMap, ToMap>(map, tmap));

       return *this;

     }

     /// \brief Make a copy of the given edge.

     ///

     /// This function makes a copy of the given edge.

     BpGraphCopy& edge(const Edge& edge, TEdge& tedge) {

       _edge_maps.push_back(new _core_bits::ItemCopy<From, Edge,

                            EdgeRefMap, TEdge>(edge, tedge));

       return *this;

     }

     /// \brief Execute copying.

     ///

     /// This function executes the copying of the graph along with the

     /// copying of the assigned data.

     void run() {

       NodeRefMap nodeRefMap(_from);

       EdgeRefMap edgeRefMap(_from);

       ArcRefMap arcRefMap(_from, _to, edgeRefMap);

       _core_bits::BpGraphCopySelector<To>::

         copy(_from, _to, nodeRefMap, edgeRefMap);

       for (int i = 0; i < int(_node_maps.size()); ++i) {

         _node_maps[i]->copy(_from, nodeRefMap);

       }

       for (int i = 0; i < int(_red_maps.size()); ++i) {

         _red_maps[i]->copy(_from, nodeRefMap);

       }

       for (int i = 0; i < int(_blue_maps.size()); ++i) {

         _blue_maps[i]->copy(_from, nodeRefMap);

       }

       for (int i = 0; i < int(_edge_maps.size()); ++i) {

         _edge_maps[i]->copy(_from, edgeRefMap);

       }

       for (int i = 0; i < int(_arc_maps.size()); ++i) {

         _arc_maps[i]->copy(_from, arcRefMap);

       }

     }

   private:

     const From& _from;

     To& _to;

     std::vector<_core_bits::MapCopyBase<From, Node, NodeRefMap>* >

       _node_maps;

     std::vector<_core_bits::MapCopyBase<From, RedNode, NodeRefMap>* >

       _red_maps;

     std::vector<_core_bits::MapCopyBase<From, BlueNode, NodeRefMap>* >

       _blue_maps;

     std::vector<_core_bits::MapCopyBase<From, Arc, ArcRefMap>* >

       _arc_maps;

     std::vector<_core_bits::MapCopyBase<From, Edge, EdgeRefMap>* >

       _edge_maps;

   };

   /// \brief Copy a graph to another graph.

   ///

   /// This function copies a graph to another graph.

   /// The complete usage of it is detailed in the BpGraphCopy class,

   /// but a short example shows a basic work:

   ///\code

   /// graphCopy(src, trg).nodeRef(nr).edgeCrossRef(ecr).run();

   ///\endcode

   ///

   /// After the copy the \c nr map will contain the mapping from the

   /// nodes of the \c from graph to the nodes of the \c to graph and

   /// \c ecr will contain the mapping from the edges of the \c to graph

   /// to the edges of the \c from graph.

   ///

   /// \see BpGraphCopy

   template <typename From, typename To>

   BpGraphCopy<From, To>

   bpGraphCopy(const From& from, To& to) {

     return BpGraphCopy<From, To>(from, to);