#include <lemon/concept_check.h>

 #include <lemon/concept/maps.h>

     MapExtender& operator=(const MapExtender& cmap) {

       return operator=<MapExtender>(cmap);

     }

     template <typename CMap>

     MapExtender& operator=(const CMap& cmap) {

       Parent::operator=(cmap);

       return *this;

     } 

   /// \ingroup graphbits

   /// 

   /// \brief Extender for maps which use a subset of the items.

   template <typename _Graph, typename _Map>

   class SubMapExtender : public _Map {

   public:

     typedef _Map Parent;

     typedef SubMapExtender Map;

     typedef _Graph Graph;

     typedef typename Parent::Key Item;

     typedef typename Parent::Key Key;

     typedef typename Parent::Value Value;

     class MapIt;

     class ConstMapIt;

     friend class MapIt;

     friend class ConstMapIt;

   public:

     SubMapExtender(const Graph& _graph) 

       : Parent(_graph), graph(_graph) {}

     SubMapExtender(const Graph& _graph, const Value& _value) 

       : Parent(_graph, _value), graph(_graph) {}

     SubMapExtender& operator=(const SubMapExtender& cmap) {

       return operator=<MapExtender>(cmap);

     }

     template <typename CMap>

     SubMapExtender& operator=(const CMap& cmap) {

       checkConcept<concept::ReadMap<Key, Value>, CMap>();

       Item it;

       for (graph.first(it); it != INVALID; graph.next(it)) {

         Parent::set(it, cmap[it]);

       }

       return *this;

     } 

     class MapIt : public Item {

     public:

       typedef Item Parent;

       typedef typename Map::Value Value;

       MapIt() {}

       MapIt(Invalid i) : Parent(i) { }

       explicit MapIt(Map& _map) : map(_map) {

         map.graph.first(*this);

       }

       MapIt(const Map& _map, const Item& item) 

 	: Parent(item), map(_map) {}

       MapIt& operator++() { 

 	map.graph.next(*this);

 	return *this; 

       }

       typename MapTraits<Map>::ConstReturnValue operator*() const {

 	return map[*this];

       }

       typename MapTraits<Map>::ReturnValue operator*() {

 	return map[*this];

       }

       void set(const Value& value) {

 	map.set(*this, value);

       }

     protected:

       Map& map;

     };

     class ConstMapIt : public Item {

     public:

       typedef Item Parent;

       typedef typename Map::Value Value;

       ConstMapIt() {}

       ConstMapIt(Invalid i) : Parent(i) { }

       explicit ConstMapIt(Map& _map) : map(_map) {

         map.graph.first(*this);

       }

       ConstMapIt(const Map& _map, const Item& item) 

 	: Parent(item), map(_map) {}

       ConstMapIt& operator++() { 

 	map.graph.next(*this);

 	return *this; 

       }

       typename MapTraits<Map>::ConstReturnValue operator*() const {

 	return map[*this];

       }

     protected:

       const Map& map;

     };

     class ItemIt : public Item {

     public:

       typedef Item Parent;

       ItemIt() {}

       ItemIt(Invalid i) : Parent(i) { }

       explicit ItemIt(Map& _map) : map(_map) {

         map.graph.first(*this);

       }

       ItemIt(const Map& _map, const Item& item) 

 	: Parent(item), map(_map) {}

       ItemIt& operator++() { 

 	map.graph.next(*this);

 	return *this; 

       }

     protected:

       const Map& map;

     };

   private:

     const Graph& graph;

   };