friend class BidirGraphWrapper<Graph>;

     protected:

       typename Graph::EdgeIt e;

       bool backward;

     public:

       EdgeIt() { }

       EdgeIt(const Invalid& i) : e(i), backward(true) { }

       EdgeIt(const BidirGraphWrapper<Graph>& _G) { 

 	backward=false;

 	_G.graph->first(e);

 	while (_G.graph->valid(e) && !_G.enabled(*this)) _G.graph->next(e);

 	if (!_G.graph->valid(e)) {

 	  backward=true;

 	  _G.graph->first(e);

 	  while (_G.graph->valid(e) && !_G.enabled(*this)) _G.graph->next(e);

 	}

       }

       operator Edge() const { 

 	return Edge(e, this->backward);

       }

     };

     using GraphWrapper<Graph>::first;

 //     NodeIt& first(NodeIt& i) const { 

 //       i=NodeIt(*this); return i;

 //     }

     OutEdgeIt& first(OutEdgeIt& i, const Node& p) const { 

       i=OutEdgeIt(*this, p); return i;

     }

 //    FIXME not tested

     InEdgeIt& first(InEdgeIt& i, const Node& p) const { 

       i=InEdgeIt(*this, p); return i;

     }

     EdgeIt& first(EdgeIt& i) const { 

       i=EdgeIt(*this); return i;

     }

     using GraphWrapper<Graph>::next;

 //    NodeIt& next(NodeIt& n) const { GraphWrapper<Graph>::next(n); return n; }

     OutEdgeIt& next(OutEdgeIt& e) const { 

       if (!e.backward) {

 	Node v=this->graph->aNode(e.out);

 	this->graph->next(e.out);

 	while(this->graph->valid(e.out) && !enabled(e)) { 

 	  this->graph->next(e.out); }

 	if (!this->graph->valid(e.out)) {

 	  e.backward=true;

 	  this->graph->first(e.in, v); 

 	  while(this->graph->valid(e.in) && !enabled(e)) { 

 	    this->graph->next(e.in); }

 	}

       } else {

 	this->graph->next(e.in);

 	while(this->graph->valid(e.in) && !enabled(e)) { 

 	  this->graph->next(e.in); } 

       }

       return e;

     }

 //     FIXME Not tested

     InEdgeIt& next(InEdgeIt& e) const { 

       if (!e.backward) {

 	Node v=this->graph->aNode(e.in);

 	this->graph->next(e.in);

 	while(this->graph->valid(e.in) && !enabled(e)) { 

 	  this->graph->next(e.in); }

 	if (!this->graph->valid(e.in)) {

 	  e.backward=true;

 	  this->graph->first(e.out, v); 

 	  while(this->graph->valid(e.out) && !enabled(e)) { 

 	    this->graph->next(e.out); }

 	}

       } else {

 	this->graph->next(e.out);

 	while(this->graph->valid(e.out) && !enabled(e)) { 

 	  this->graph->next(e.out); } 

       }

       return e;

     }

     EdgeIt& next(EdgeIt& e) const {

       if (!e.backward) {

 	this->graph->next(e.e);

 	while(this->graph->valid(e.e) && !enabled(e)) { 

 	  this->graph->next(e.e); }

 	if (!this->graph->valid(e.e)) {

 	  e.backward=true;

 	  this->graph->first(e.e); 

 	  while(this->graph->valid(e.e) && !enabled(e)) { 

 	    this->graph->next(e.e); }

 	}

       } else {

 	this->graph->next(e.e);

 	while(this->graph->valid(e.e) && !enabled(e)) { 

 	  this->graph->next(e.e); } 

       }

       return e;

     }

     Node tail(Edge e) const { 

       return ((!e.backward) ? this->graph->tail(e) : this->graph->head(e)); }

     Node head(Edge e) const { 

       return ((!e.backward) ? this->graph->head(e) : this->graph->tail(e)); }

     Node aNode(OutEdgeIt e) const { 

       return ((!e.backward) ? this->graph->aNode(e.out) : 

 	      this->graph->aNode(e.in)); }

     Node bNode(OutEdgeIt e) const { 

       return ((!e.backward) ? this->graph->bNode(e.out) : 

 	      this->graph->bNode(e.in)); }

     Node aNode(InEdgeIt e) const { 

       return ((!e.backward) ? this->graph->aNode(e.in) : 

 	      this->graph->aNode(e.out)); }

     Node bNode(InEdgeIt e) const { 

       return ((!e.backward) ? this->graph->bNode(e.in) : 

 	      this->graph->bNode(e.out)); }

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

     //FIXME

     void edgeNum() const { }

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

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

     bool valid(Node n) const { return GraphWrapper<Graph>::valid(n); }

     bool valid(Edge e) const { 

       return this->graph->valid(e);

 	//return e.forward ? graph->valid(e.out) : graph->valid(e.in); 

     }

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

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

 //     void augment(const Edge& e, Number a) const {

 //       if (!e.backward)  

 // // 	flow->set(e.out, flow->get(e.out)+a);

 // 	flow->set(e, (*flow)[e]+a);

 //       else  

 // // 	flow->set(e.in, flow->get(e.in)-a);

 // 	flow->set(e, (*flow)[e]-a);

 //     }

     bool enabled(const Edge& e) const { 

       if (!e.backward) 

 //	return (capacity->get(e.out)-flow->get(e.out)); 

 	//return ((*capacity)[e]-(*flow)[e]);

 	return true;

       else 

 //	return (flow->get(e.in)); 

 	//return ((*flow)[e]); 

 	return true;

     }

 //     Number enabled(typename Graph::OutEdgeIt out) const { 

 // //      return (capacity->get(out)-flow->get(out)); 

 //       return ((*capacity)[out]-(*flow)[out]); 

 //     }

 //     Number enabled(typename Graph::InEdgeIt in) const { 

 // //      return (flow->get(in)); 

 //       return ((*flow)[in]); 

 //     }

     template <typename T>

     class EdgeMap {

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

     public:

       EdgeMap(const BidirGraphWrapper<Graph>& _G) : forward_map(*(_G.graph)), backward_map(*(_G.graph)) { }

       EdgeMap(const BidirGraphWrapper<Graph>& _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.out, a); 

 	else 

 	  backward_map.set(e.in, a); 

       }

       T operator[](Edge e) const { 

 	if (!e.backward) 

 	  return forward_map[e.out]; 

 	else 

 	  return backward_map[e.in]; 

       }

 //       T get(Edge e) const { 

 // 	if (e.out_or_in) 

 // 	  return forward_map.get(e.out); 

 // 	else 

 // 	  return backward_map.get(e.in); 

 //       }

     };

   };

   /// A wrapper for composing the residual graph for directed flow and circulation problems.

   /// A wrapper for composing the residual graph for directed flow and circulation problems.

   template<typename Graph, typename Number, 

 	   typename CapacityMap, typename FlowMap>

   class ResGraphWrapper : public GraphWrapper<Graph> {

   protected:

     const CapacityMap* capacity;

     FlowMap* flow;

     ResGraphWrapper() : GraphWrapper<Graph>(0), 

 			capacity(0), flow(0) { }

     void setCapacityMap(const CapacityMap& _capacity) {

       capacity=&_capacity;

     }

     void setFlowMap(FlowMap& _flow) {

       flow=&_flow;

     }

   public:

     ResGraphWrapper(Graph& _graph, const CapacityMap& _capacity, 

 		    FlowMap& _flow) : 

       GraphWrapper<Graph>(_graph), capacity(&_capacity), flow(&_flow) { }

     class Edge; 

     class OutEdgeIt; 

     friend class Edge; 

     friend class OutEdgeIt; 

     typedef typename GraphWrapper<Graph>::Node Node;

     typedef typename GraphWrapper<Graph>::NodeIt NodeIt;

     class Edge : public Graph::Edge {

       friend class ResGraphWrapper<Graph, Number, CapacityMap, FlowMap>;

     protected:

       bool backward; //true, iff backward

 //      typename Graph::Edge e;

     public:

       Edge() { }

       Edge(const typename Graph::Edge& _e, bool _backward) : 

 	Graph::Edge(_e), backward(_backward) { }

       Edge(const Invalid& i) : Graph::Edge(i), backward(true) { }

 //the unique invalid iterator

       friend bool operator==(const Edge& u, const Edge& v) { 

 	return (v.backward==u.backward && 

 		static_cast<typename Graph::Edge>(u)==

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

       } 

       friend bool operator!=(const Edge& u, const Edge& v) { 

 	return (v.backward!=u.backward || 

 		static_cast<typename Graph::Edge>(u)!=

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

       } 

     };

     class OutEdgeIt {

       friend class ResGraphWrapper<Graph, Number, CapacityMap, FlowMap>;

     protected:

       typename Graph::OutEdgeIt out;

       typename Graph::InEdgeIt in;

       bool backward;

     public:

       OutEdgeIt() { }

       //FIXME

 //      OutEdgeIt(const Edge& e) : Edge(e) { }

       OutEdgeIt(const Invalid& i) : out(i), in(i), backward(true) { }

 //the unique invalid iterator

       OutEdgeIt(const ResGraphWrapper<Graph, Number, CapacityMap, FlowMap>& _G, Node v) { 

 	backward=false;

 	_G.graph->first(out, v);

 	while( _G.graph->valid(out) && !(_G.resCap(*this)>0) ) { _G.graph->next(out); }

 	if (!_G.graph->valid(out)) {

 	  backward=true;

 	  _G.graph->first(in, v);

 	  while( _G.graph->valid(in) && !(_G.resCap(*this)>0) ) { _G.graph->next(in); }

 	}

       }

       operator Edge() const { 

 //	Edge e;

 //	e.forward=this->forward;

 //	if (this->forward) e=out; else e=in;

 //	return e;

 	if (this->backward) 

 	  return Edge(in, this->backward); 

 	else 

 	  return Edge(out, this->backward);

       }

     };

     class InEdgeIt {

       friend class ResGraphWrapper<Graph, Number, CapacityMap, FlowMap>;

     protected:

       typename Graph::OutEdgeIt out;

       typename Graph::InEdgeIt in;

       bool backward;

     public:

       InEdgeIt() { }

       //FIXME

 //      OutEdgeIt(const Edge& e) : Edge(e) { }

       InEdgeIt(const Invalid& i) : out(i), in(i), backward(true) { }

 //the unique invalid iterator

       InEdgeIt(const ResGraphWrapper<Graph, Number, CapacityMap, FlowMap>& _G, Node v) { 

 	backward=false;

 	_G.graph->first(in, v);

 	while( _G.graph->valid(in) && !(_G.resCap(*this)>0) ) { _G.graph->next(in); }

 	if (!_G.graph->valid(in)) {

 	  backward=true;

 	  _G.graph->first(out, v);

 	  while( _G.graph->valid(out) && !(_G.resCap(*this)>0) ) { _G.graph->next(out); }

 	}

       }

       operator Edge() const { 

 //	Edge e;

 //	e.forward=this->forward;

 //	if (this->forward) e=out; else e=in;

 //	return e;

 	if (this->backward) 

 	  return Edge(out, this->backward); 

 	else 

 	  return Edge(in, this->backward);

       }

     };

     class EdgeIt {