#ifndef NODE_MAP_BASE_H

 #define NODE_MAP_BASE_H

 template <class G, class K>

 class NodeMapBase {

 public:

 	typedef G Graph;

 	typedef K KeyType;

 	MapBase() : graph(0) {}

 	MapBase(Graph& g) : graph(&g) {graph.node_maps.add(*this);}

 	virtual ~MapBase() {graph.node_maps.erase(*this);}	

 protected:

 	Graph* graph;

 	int graph_index;

 	virtual void add(const KeyType&) = 0;

 	virtual void erase(const KeyType&) = 0;

 	friend class Graph;

 };

 #endif