/// \ingroup graphbits

   ///

   /// \brief Extender for the BpUGraphAdaptors

   template <typename Base>

   class BpUGraphAdaptorExtender : public Base {

   public:

     typedef Base Parent;

     typedef BpUGraphAdaptorExtender Graph;

     typedef typename Parent::Node Node;

     typedef typename Parent::BNode BNode;

     typedef typename Parent::ANode ANode;

     typedef typename Parent::Edge Edge;

     typedef typename Parent::UEdge UEdge;

     Node oppositeNode(const UEdge& edge, const Node& node) const {

       return source(edge) == node ? 

 	target(edge) : source(edge);

     }

     int maxId(Node) const {

       return Parent::maxNodeId();

     }

     int maxId(BNode) const {

       return Parent::maxBNodeId();

     }

     int maxId(ANode) const {

       return Parent::maxANodeId();

     }

     int maxId(Edge) const {

       return Parent::maxEdgeId();

     }

     int maxId(UEdge) const {

       return Parent::maxUEdgeId();

     }

     Node fromId(int id, Node) const {

       return Parent::nodeFromId(id);

     }

     ANode fromId(int id, ANode) const {

       return Parent::fromANodeId(id);

     }

     BNode fromId(int id, BNode) const {

       return Parent::fromBNodeId(id);

     }

     Edge fromId(int id, Edge) const {

       return Parent::edgeFromId(id);

     }

     UEdge fromId(int id, UEdge) const {

       return Parent::uEdgeFromId(id);

     }  

     class NodeIt : public Node { 

       const Graph* graph;

     public:

       NodeIt() { }

       NodeIt(Invalid i) : Node(INVALID) { }

       explicit NodeIt(const Graph& _graph) : graph(&_graph) {

 	graph->first(static_cast<Node&>(*this));

       }

       NodeIt(const Graph& _graph, const Node& node) 

 	: Node(node), graph(&_graph) { }

       NodeIt& operator++() { 

 	graph->next(*this);

 	return *this; 

       }

     };

     class ANodeIt : public Node { 

       friend class BpUGraphAdaptorExtender;

       const Graph* graph;

     public:

       ANodeIt() { }

       ANodeIt(Invalid i) : Node(INVALID) { }

       explicit ANodeIt(const Graph& _graph) : graph(&_graph) {

 	graph->firstANode(static_cast<Node&>(*this));

       }

       ANodeIt(const Graph& _graph, const Node& node) 

 	: Node(node), graph(&_graph) {}

       ANodeIt& operator++() { 

 	graph->nextANode(*this);

 	return *this; 

       }

     };

     class BNodeIt : public Node { 

       friend class BpUGraphAdaptorExtender;

       const Graph* graph;

     public:

       BNodeIt() { }

       BNodeIt(Invalid i) : Node(INVALID) { }

       explicit BNodeIt(const Graph& _graph) : graph(&_graph) {

 	graph->firstBNode(static_cast<Node&>(*this));

       }

       BNodeIt(const Graph& _graph, const Node& node) 

 	: Node(node), graph(&_graph) {}

       BNodeIt& operator++() { 

 	graph->nextBNode(*this);

 	return *this; 

       }

     };

     class EdgeIt : public Edge { 

       friend class BpUGraphAdaptorExtender;

       const Graph* graph;

     public:

       EdgeIt() { }

       EdgeIt(Invalid i) : Edge(INVALID) { }

       explicit EdgeIt(const Graph& _graph) : graph(&_graph) {

 	graph->first(static_cast<Edge&>(*this));

       }

       EdgeIt(const Graph& _graph, const Edge& edge) 

 	: Edge(edge), graph(&_graph) { }

       EdgeIt& operator++() { 

 	graph->next(*this);

 	return *this; 

       }

     };

     class UEdgeIt : public UEdge { 

       friend class BpUGraphAdaptorExtender;

       const Graph* graph;

     public:

       UEdgeIt() { }

       UEdgeIt(Invalid i) : UEdge(INVALID) { }

       explicit UEdgeIt(const Graph& _graph) : graph(&_graph) {

 	graph->first(static_cast<UEdge&>(*this));

       }

       UEdgeIt(const Graph& _graph, const UEdge& edge) 

 	: UEdge(edge), graph(&_graph) { }

       UEdgeIt& operator++() { 

 	graph->next(*this);

 	return *this; 

       }

     };

     class OutEdgeIt : public Edge { 

       friend class BpUGraphAdaptorExtender;

       const Graph* graph;

     public:

       OutEdgeIt() { }

       OutEdgeIt(Invalid i) : Edge(i) { }

       OutEdgeIt(const Graph& _graph, const Node& node) 

 	: graph(&_graph) {

 	graph->firstOut(*this, node);

       }

       OutEdgeIt(const Graph& _graph, const Edge& edge) 

 	: Edge(edge), graph(&_graph) {}

       OutEdgeIt& operator++() { 

 	graph->nextOut(*this);

 	return *this; 

       }

     };

     class InEdgeIt : public Edge { 

       friend class BpUGraphAdaptorExtender;

       const Graph* graph;

     public:

       InEdgeIt() { }

       InEdgeIt(Invalid i) : Edge(i) { }

       InEdgeIt(const Graph& _graph, const Node& node) 

 	: graph(&_graph) {

 	graph->firstIn(*this, node);

       }

       InEdgeIt(const Graph& _graph, const Edge& edge) : 

 	Edge(edge), graph(&_graph) {}

       InEdgeIt& operator++() { 

 	graph->nextIn(*this);

 	return *this; 

       }

     };

     /// \brief Base node of the iterator

     ///

     /// Returns the base node (ie. the source in this case) of the iterator

     Node baseNode(const OutEdgeIt &e) const {

       return Parent::source((Edge&)e);

     }

     /// \brief Running node of the iterator

     ///

     /// Returns the running node (ie. the target in this case) of the

     /// iterator

     Node runningNode(const OutEdgeIt &e) const {

       return Parent::target((Edge&)e);

     }

     /// \brief Base node of the iterator

     ///

     /// Returns the base node (ie. the target in this case) of the iterator

     Node baseNode(const InEdgeIt &e) const {

       return Parent::target((Edge&)e);

     }

     /// \brief Running node of the iterator

     ///

     /// Returns the running node (ie. the source in this case) of the

     /// iterator

     Node runningNode(const InEdgeIt &e) const {

       return Parent::source((Edge&)e);

     }

     class IncEdgeIt : public Parent::UEdge { 

       friend class BpUGraphAdaptorExtender;

       const Graph* graph;

       bool direction;

     public:

       IncEdgeIt() { }

       IncEdgeIt(Invalid i) : UEdge(i), direction(true) { }

       IncEdgeIt(const Graph& _graph, const Node &n) : graph(&_graph) {

 	graph->firstInc(*this, direction, n);

       }

       IncEdgeIt(const Graph& _graph, const UEdge &ue, const Node &n)

 	: graph(&_graph), UEdge(ue) {

 	direction = (graph->source(ue) == n);

       }

       IncEdgeIt& operator++() {

 	graph->nextInc(*this, direction);

 	return *this; 

       }

     };

     /// Base node of the iterator

     ///

     /// Returns the base node of the iterator

     Node baseNode(const IncEdgeIt &e) const {

       return e.direction ? source(e) : target(e);

     }

     /// Running node of the iterator

     ///

     /// Returns the running node of the iterator

     Node runningNode(const IncEdgeIt &e) const {

       return e.direction ? target(e) : source(e);

     }

   };