template <typename _Graph, bool _dir, typename _Map, 

 	      typename _Converter = DefaultConverter<typename _Map::Value> >

     class GraphArcMapStorage : public MapStorageBase<typename _Graph::Edge> {

     public:

       typedef _Map Map;

       typedef _Converter Converter;

       typedef _Graph Graph;

       typedef typename Graph::Edge Item;

       static const bool dir = _dir;

     private:

       const Graph& _graph;

       Map& _map;

       Converter _converter;

     public:

       GraphArcMapStorage(const Graph& graph, Map& map, 

 			 const Converter& converter = Converter()) 

 	: _graph(graph), _map(map), _converter(converter) {}

       virtual ~GraphArcMapStorage() {}

       virtual void set(const Item& item ,const std::string& value) {

 	_map.set(_graph.direct(item, dir), _converter(value));

       }

     };

       }

     };

     template <typename Graph>

     struct GraphArcLookUpConverter {

       const Graph& _graph;

       const std::map<std::string, typename Graph::Edge>& _map;

       GraphArcLookUpConverter(const Graph& graph, 

 			      const std::map<std::string,

 			                     typename Graph::Edge>& map) 

 	: _graph(graph), _map(map) {}

       typename Graph::Arc operator()(const std::string& str) {

 	if (str.empty() || (str[0] != '+' && str[0] != '-')) {

 	  throw DataFormatError("Item must start with '+' or '-'");

 	}

 	typename std::map<std::string, typename Graph::Edge>

 	  ::const_iterator it = _map.find(str.substr(1));

 	if (it == _map.end()) {

 	  throw DataFormatError("Item not found");

 	}

 	return _graph.direct(it->second, str[0] == '+');

   /// \ingroup lemon_io

   ///  

   /// \brief LGF reader for undirected graphs

   ///

   /// This utility reads an \ref lgf-format "LGF" file.

   template <typename _Graph>

   class GraphReader {

   public:

     typedef _Graph Graph;

     TEMPLATE_GRAPH_TYPEDEFS(Graph);

   private:

     std::istream* _is;

     bool local_is;

     Graph& _graph;

     std::string _nodes_caption;

     std::string _edges_caption;

     std::string _attributes_caption;

     typedef std::map<std::string, Node> NodeIndex;

     NodeIndex _node_index;

     typedef std::map<std::string, Edge> EdgeIndex;

     EdgeIndex _edge_index;

     typedef std::vector<std::pair<std::string, 

       _reader_bits::MapStorageBase<Node>*> > NodeMaps;    

     NodeMaps _node_maps; 

     typedef std::vector<std::pair<std::string,

       _reader_bits::MapStorageBase<Edge>*> > EdgeMaps;

     EdgeMaps _edge_maps;

     typedef std::multimap<std::string, _reader_bits::ValueStorageBase*> 

       Attributes;

     Attributes _attributes;

     typedef std::map<std::string, _reader_bits::Section*> Sections;

     Sections _sections;

     bool _use_nodes;

     bool _use_edges;

     int line_num;

     std::istringstream line;

   public:

     /// \brief Constructor

     ///

     /// Construct a undirected graph reader, which reads from the given

     /// input stream.

     GraphReader(std::istream& is, Graph& graph) 

       : _is(&is), local_is(false), _graph(graph),

 	_use_nodes(false), _use_edges(false) {}

     /// \brief Constructor

     ///

     /// Construct a undirected graph reader, which reads from the given

     /// file.

     GraphReader(const std::string& fn, Graph& graph) 

       : _is(new std::ifstream(fn.c_str())), local_is(true), _graph(graph),

     	_use_nodes(false), _use_edges(false) {}

     /// \brief Constructor

     ///

     /// Construct a undirected graph reader, which reads from the given

     /// file.

     GraphReader(const char* fn, Graph& graph) 

       : _is(new std::ifstream(fn)), local_is(true), _graph(graph),

     	_use_nodes(false), _use_edges(false) {}

     /// \brief Copy constructor

     ///

     /// The copy constructor transfers all data from the other reader,

     /// therefore the copied reader will not be usable more. 

     GraphReader(GraphReader& other) 

       : _is(other._is), local_is(other.local_is), _graph(other._graph),

 	_use_nodes(other._use_nodes), _use_edges(other._use_edges) {

       other._is = 0;

       other.local_is = false;

       _node_index.swap(other._node_index);

       _edge_index.swap(other._edge_index);

       _node_maps.swap(other._node_maps);

       _edge_maps.swap(other._edge_maps);

       _attributes.swap(other._attributes);

       _nodes_caption = other._nodes_caption;

       _edges_caption = other._edges_caption;

       _attributes_caption = other._attributes_caption;

       _sections.swap(other._sections);

     }

     /// \brief Destructor

     ~GraphReader() {

       for (typename NodeMaps::iterator it = _node_maps.begin(); 

 	   it != _node_maps.end(); ++it) {

 	delete it->second;

       }

       for (typename EdgeMaps::iterator it = _edge_maps.begin(); 

 	   it != _edge_maps.end(); ++it) {

 	delete it->second;

       }

       for (typename Attributes::iterator it = _attributes.begin(); 

 	   it != _attributes.end(); ++it) {

 	delete it->second;

       }

       for (typename Sections::iterator it = _sections.begin(); 

 	   it != _sections.end(); ++it) {

 	delete it->second;

       }

       if (local_is) {

 	delete _is;

       }

     }

   private:

     GraphReader& operator=(const GraphReader&);

   public:

     /// \name Reading rules

     /// @{

     /// \brief Node map reading rule

     ///

     /// Add a node map reading rule to the reader.

     template <typename Map>

     GraphReader& nodeMap(const std::string& caption, Map& map) {

       checkConcept<concepts::WriteMap<Node, typename Map::Value>, Map>();

       _reader_bits::MapStorageBase<Node>* storage = 

 	new _reader_bits::MapStorage<Node, Map>(map);

       _node_maps.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Node map reading rule

     ///

     /// Add a node map reading rule with specialized converter to the

     /// reader.

     template <typename Map, typename Converter>

     GraphReader& nodeMap(const std::string& caption, Map& map, 

 			   const Converter& converter = Converter()) {

       checkConcept<concepts::WriteMap<Node, typename Map::Value>, Map>();

       _reader_bits::MapStorageBase<Node>* storage = 

 	new _reader_bits::MapStorage<Node, Map, Converter>(map, converter);

       _node_maps.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Edge map reading rule

     ///

     /// Add an edge map reading rule to the reader.

     template <typename Map>

     GraphReader& edgeMap(const std::string& caption, Map& map) {

       checkConcept<concepts::WriteMap<Edge, typename Map::Value>, Map>();

       _reader_bits::MapStorageBase<Edge>* storage = 

 	new _reader_bits::MapStorage<Edge, Map>(map);

       _edge_maps.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Edge map reading rule

     ///

     /// Add an edge map reading rule with specialized converter to the

     /// reader.

     template <typename Map, typename Converter>

     GraphReader& edgeMap(const std::string& caption, Map& map, 

 			  const Converter& converter = Converter()) {

       checkConcept<concepts::WriteMap<Edge, typename Map::Value>, Map>();

       _reader_bits::MapStorageBase<Edge>* storage = 

 	new _reader_bits::MapStorage<Edge, Map, Converter>(map, converter);

       _edge_maps.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Arc map reading rule

     ///

     /// Add an arc map reading rule to the reader.

     template <typename Map>

     GraphReader& arcMap(const std::string& caption, Map& map) {

       checkConcept<concepts::WriteMap<Arc, typename Map::Value>, Map>();

       _reader_bits::MapStorageBase<Edge>* forward_storage = 

 	new _reader_bits::GraphArcMapStorage<Graph, true, Map>(_graph, map);

       _edge_maps.push_back(std::make_pair('+' + caption, forward_storage));

       _reader_bits::MapStorageBase<Edge>* backward_storage = 

 	new _reader_bits::GraphArcMapStorage<Graph, false, Map>(_graph, map);

       _edge_maps.push_back(std::make_pair('-' + caption, backward_storage));

       return *this;

     }

     /// \brief Arc map reading rule

     ///

     /// Add an arc map reading rule with specialized converter to the

     /// reader.

     template <typename Map, typename Converter>

     GraphReader& arcMap(const std::string& caption, Map& map, 

 			  const Converter& converter = Converter()) {

       checkConcept<concepts::WriteMap<Arc, typename Map::Value>, Map>();

       _reader_bits::MapStorageBase<Edge>* forward_storage = 

 	new _reader_bits::GraphArcMapStorage<Graph, true, Map, Converter>

 	(_graph, map, converter);

       _edge_maps.push_back(std::make_pair('+' + caption, forward_storage));

       _reader_bits::MapStorageBase<Edge>* backward_storage = 

 	new _reader_bits::GraphArcMapStorage<Graph, false, Map, Converter>

 	(_graph, map, converter);

       _edge_maps.push_back(std::make_pair('-' + caption, backward_storage));

       return *this;

     }

     /// \brief Attribute reading rule

     ///

     /// Add an attribute reading rule to the reader.

     template <typename Value>

     GraphReader& attribute(const std::string& caption, Value& value) {

       _reader_bits::ValueStorageBase* storage = 

 	new _reader_bits::ValueStorage<Value>(value);

       _attributes.insert(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Attribute reading rule

     ///

     /// Add an attribute reading rule with specialized converter to the

     /// reader.

     template <typename Value, typename Converter>

     GraphReader& attribute(const std::string& caption, Value& value, 

 			     const Converter& converter = Converter()) {

       _reader_bits::ValueStorageBase* storage = 

 	new _reader_bits::ValueStorage<Value, Converter>(value, converter);

       _attributes.insert(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Node reading rule

     ///

     /// Add a node reading rule to reader.

     GraphReader& node(const std::string& caption, Node& node) {

       typedef _reader_bits::MapLookUpConverter<Node> Converter;

       Converter converter(_node_index);

       _reader_bits::ValueStorageBase* storage = 

 	new _reader_bits::ValueStorage<Node, Converter>(node, converter);

       _attributes.insert(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Edge reading rule

     ///

     /// Add an edge reading rule to reader.

     GraphReader& edge(const std::string& caption, Edge& edge) {

       typedef _reader_bits::MapLookUpConverter<Edge> Converter;

       Converter converter(_edge_index);

       _reader_bits::ValueStorageBase* storage = 

 	new _reader_bits::ValueStorage<Edge, Converter>(edge, converter);

       _attributes.insert(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Arc reading rule

     ///

     /// Add an arc reading rule to reader.

     GraphReader& arc(const std::string& caption, Arc& arc) {

       typedef _reader_bits::GraphArcLookUpConverter<Graph> Converter;

       Converter converter(_graph, _edge_index);

       _reader_bits::ValueStorageBase* storage = 

 	new _reader_bits::ValueStorage<Arc, Converter>(arc, converter);

       _attributes.insert(std::make_pair(caption, storage));

       return *this;

     }

     /// @}

     /// \name Select section by name

     /// @{

     /// \brief Set \c \@nodes section to be read

     ///

     /// Set \c \@nodes section to be read

     GraphReader& nodes(const std::string& caption) {

       _nodes_caption = caption;

       return *this;

     }

     /// \brief Set \c \@edges section to be read

     ///

     /// Set \c \@edges section to be read

     GraphReader& edges(const std::string& caption) {

       _edges_caption = caption;

       return *this;

     }

     /// \brief Set \c \@attributes section to be read

     ///

     /// Set \c \@attributes section to be read

     GraphReader& attributes(const std::string& caption) {

       _attributes_caption = caption;

       return *this;

     }

     /// @}

     /// \name Section readers

     /// @{

     /// \brief Add a section processor with line oriented reading

     ///

     /// In the \e LGF file extra sections can be placed, which contain

     /// any data in arbitrary format. These sections can be read with

     /// this function line by line. The first parameter is the type

     /// descriptor of the section, the second is a functor, which

     /// takes just one \c std::string parameter. At the reading

     /// process, each line of the section will be given to the functor

     /// object. However, the empty lines and the comment lines are

     /// filtered out, and the leading whitespaces are stipped from

     /// each processed string.

     ///

     /// For example let's see a section, which contain several

     /// integers, which should be inserted into a vector.

     ///\code

     ///  @numbers

     ///  12 45 23

     ///  4

     ///  23 6

     ///\endcode

     ///

     /// The functor is implemented as an struct:

     ///\code

     ///  struct NumberSection {

     ///    std::vector<int>& _data;

     ///    NumberSection(std::vector<int>& data) : _data(data) {}

     ///    void operator()(const std::string& line) {

     ///      std::istringstream ls(line);

     ///      int value;

     ///      while (ls >> value) _data.push_back(value);

     ///    }

     ///  };

     ///

     ///  // ...

     ///

     ///  reader.sectionLines("numbers", NumberSection(vec));  

     ///\endcode

     template <typename Functor>

     GraphReader& sectionLines(const std::string& type, Functor functor) {

       LEMON_ASSERT(!type.empty(), "Type is not empty.");

       LEMON_ASSERT(_sections.find(type) == _sections.end(), 

 		   "Multiple reading of section.");

       LEMON_ASSERT(type != "nodes" && type != "arcs" && type != "edges" &&

 		   type != "attributes", "Multiple reading of section.");

       _sections.insert(std::make_pair(type, 

         new _reader_bits::LineSection<Functor>(functor)));

       return *this;

     }

     /// \brief Add a section processor with stream oriented reading

     ///

     /// In the \e LGF file extra sections can be placed, which contain

     /// any data in arbitrary format. These sections can be read

     /// directly with this function. The first parameter is the type

     /// of the section, the second is a functor, which takes an \c

     /// std::istream& and an int& parameter, the latter regard to the

     /// line number of stream. The functor can read the input while

     /// the section go on, and the line number should be modified

     /// accordingly.

     template <typename Functor>

     GraphReader& sectionStream(const std::string& type, Functor functor) {

       LEMON_ASSERT(!type.empty(), "Type is not empty.");

       LEMON_ASSERT(_sections.find(type) == _sections.end(), 

 		   "Multiple reading of section.");

       LEMON_ASSERT(type != "nodes" && type != "arcs" && type != "edges" &&

 		   type != "attributes", "Multiple reading of section.");

       _sections.insert(std::make_pair(type, 

 	 new _reader_bits::StreamSection<Functor>(functor)));

       return *this;

     }    

     /// @}

     /// \name Using previously constructed node or edge set

     /// @{

     /// \brief Use previously constructed node set

     ///

     /// Use previously constructed node set, and specify the node

     /// label map.

     template <typename Map>

     GraphReader& useNodes(const Map& map) {

       checkConcept<concepts::ReadMap<Node, typename Map::Value>, Map>();

       LEMON_ASSERT(!_use_nodes, "Multiple usage of useNodes() member"); 

       _use_nodes = true;

       _writer_bits::DefaultConverter<typename Map::Value> converter;

       for (NodeIt n(_graph); n != INVALID; ++n) {

 	_node_index.insert(std::make_pair(converter(map[n]), n));

       }

       return *this;

     }

     /// \brief Use previously constructed node set

     ///

     /// Use previously constructed node set, and specify the node

     /// label map and a functor which converts the label map values to

     /// std::string.

     template <typename Map, typename Converter>

     GraphReader& useNodes(const Map& map, 

 			    const Converter& converter = Converter()) {

       checkConcept<concepts::ReadMap<Node, typename Map::Value>, Map>();

       LEMON_ASSERT(!_use_nodes, "Multiple usage of useNodes() member"); 

       _use_nodes = true;

       for (NodeIt n(_graph); n != INVALID; ++n) {

 	_node_index.insert(std::make_pair(converter(map[n]), n));

       }

       return *this;

     }

     /// \brief Use previously constructed edge set

     ///

     /// Use previously constructed edge set, and specify the edge

     /// label map.

     template <typename Map>

     GraphReader& useEdges(const Map& map) {

       checkConcept<concepts::ReadMap<Edge, typename Map::Value>, Map>();

       LEMON_ASSERT(!_use_edges, "Multiple usage of useEdges() member");

       _use_edges = true;

       _writer_bits::DefaultConverter<typename Map::Value> converter;

       for (EdgeIt a(_graph); a != INVALID; ++a) {

 	_edge_index.insert(std::make_pair(converter(map[a]), a));

       }

       return *this;

     }

     /// \brief Use previously constructed edge set

     ///

     /// Use previously constructed edge set, and specify the edge

     /// label map and a functor which converts the label map values to

     /// std::string.

     template <typename Map, typename Converter>

     GraphReader& useEdges(const Map& map, 

 			    const Converter& converter = Converter()) {

       checkConcept<concepts::ReadMap<Edge, typename Map::Value>, Map>();

       LEMON_ASSERT(!_use_edges, "Multiple usage of useEdges() member"); 

       _use_edges = true;

       for (EdgeIt a(_graph); a != INVALID; ++a) {

 	_edge_index.insert(std::make_pair(converter(map[a]), a));

       }

       return *this;

     }

     /// @}

   private:

     bool readLine() {

       std::string str;

       while(++line_num, std::getline(*_is, str)) {

 	line.clear(); line.str(str);

 	char c;

 	if (line >> std::ws >> c && c != '#') {

 	  line.putback(c);

 	  return true;

 	}

       }

       return false;

     }

     bool readSuccess() {

       return static_cast<bool>(*_is);

     }

     void skipSection() {

       char c;

       while (readSuccess() && line >> c && c != '@') {

 	readLine();

       }

       line.putback(c);

     }

     void readNodes() {

       std::vector<int> map_index(_node_maps.size());

       int map_num, label_index;

       if (!readLine()) 

 	throw DataFormatError("Cannot find map captions");

       {

 	std::map<std::string, int> maps;

 	std::string map;

 	int index = 0;

 	while (_reader_bits::readToken(line, map)) {

 	  if (maps.find(map) != maps.end()) {

 	    std::ostringstream msg;

 	    msg << "Multiple occurence of node map: " << map;

 	    throw DataFormatError(msg.str().c_str());

 	  }

 	  maps.insert(std::make_pair(map, index));

 	  ++index;

 	}

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

 	  std::map<std::string, int>::iterator jt = 

 	    maps.find(_node_maps[i].first);

 	  if (jt == maps.end()) {

 	    std::ostringstream msg;

 	    msg << "Map not found in file: " << _node_maps[i].first;

 	    throw DataFormatError(msg.str().c_str());

 	  }

 	  map_index[i] = jt->second;

 	}

 	{

 	  std::map<std::string, int>::iterator jt = maps.find("label");

 	  if (jt == maps.end())

 	    throw DataFormatError("Label map not found in file");

 	  label_index = jt->second;

 	}

 	map_num = maps.size();

       }

       char c;

       while (readLine() && line >> c && c != '@') {

 	line.putback(c);

 	std::vector<std::string> tokens(map_num);

 	for (int i = 0; i < map_num; ++i) {

 	  if (!_reader_bits::readToken(line, tokens[i])) {

 	    std::ostringstream msg;

 	    msg << "Column not found (" << i + 1 << ")";

 	    throw DataFormatError(msg.str().c_str());

 	  }

 	}

 	if (line >> std::ws >> c)

 	  throw DataFormatError("Extra character on the end of line");

 	Node n;

 	if (!_use_nodes) {

 	  n = _graph.addNode();

 	  _node_index.insert(std::make_pair(tokens[label_index], n));

 	} else {

 	  typename std::map<std::string, Node>::iterator it =

 	    _node_index.find(tokens[label_index]);

 	  if (it == _node_index.end()) {

 	    std::ostringstream msg;

 	    msg << "Node with label not found: " << tokens[label_index];

 	    throw DataFormatError(msg.str().c_str());	    

 	  }

 	  n = it->second;

 	}

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

 	  _node_maps[i].second->set(n, tokens[map_index[i]]);

 	}

       }

       if (readSuccess()) {

 	line.putback(c);

       }

     }

     void readEdges() {

       std::vector<int> map_index(_edge_maps.size());

       int map_num, label_index;

       if (!readLine()) 

 	throw DataFormatError("Cannot find map captions");

       {

 	std::map<std::string, int> maps;

 	std::string map;

 	int index = 0;

 	while (_reader_bits::readToken(line, map)) {

 	  if (maps.find(map) != maps.end()) {

 	    std::ostringstream msg;

 	    msg << "Multiple occurence of edge map: " << map;

 	    throw DataFormatError(msg.str().c_str());

 	  }

 	  maps.insert(std::make_pair(map, index));

 	  ++index;

 	}

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

 	  std::map<std::string, int>::iterator jt = 

 	    maps.find(_edge_maps[i].first);

 	  if (jt == maps.end()) {

 	    std::ostringstream msg;

 	    msg << "Map not found in file: " << _edge_maps[i].first;

 	    throw DataFormatError(msg.str().c_str());

 	  }

 	  map_index[i] = jt->second;

 	}

 	{

 	  std::map<std::string, int>::iterator jt = maps.find("label");

 	  if (jt == maps.end())

 	    throw DataFormatError("Label map not found in file");

 	  label_index = jt->second;

 	}

 	map_num = maps.size();

       }

       char c;

       while (readLine() && line >> c && c != '@') {

 	line.putback(c);

 	std::string source_token;

 	std::string target_token;

 	if (!_reader_bits::readToken(line, source_token))

 	  throw DataFormatError("Source not found");

 	if (!_reader_bits::readToken(line, target_token))

 	  throw DataFormatError("Source not found");

 	std::vector<std::string> tokens(map_num);

 	for (int i = 0; i < map_num; ++i) {

 	  if (!_reader_bits::readToken(line, tokens[i])) {

 	    std::ostringstream msg;

 	    msg << "Column not found (" << i + 1 << ")";

 	    throw DataFormatError(msg.str().c_str());

 	  }

 	}

 	if (line >> std::ws >> c)

 	  throw DataFormatError("Extra character on the end of line");

 	Edge e;

 	if (!_use_edges) {

           typename NodeIndex::iterator it;

           it = _node_index.find(source_token);

           if (it == _node_index.end()) {

             std::ostringstream msg;

             msg << "Item not found: " << source_token;

             throw DataFormatError(msg.str().c_str());

           }

           Node source = it->second;

           it = _node_index.find(target_token);

           if (it == _node_index.end()) {       

             std::ostringstream msg;            

             msg << "Item not found: " << target_token;

             throw DataFormatError(msg.str().c_str());

           }                                          

           Node target = it->second;                            

 	  e = _graph.addEdge(source, target);

 	  _edge_index.insert(std::make_pair(tokens[label_index], e));

 	} else {

 	  typename std::map<std::string, Edge>::iterator it =

 	    _edge_index.find(tokens[label_index]);

 	  if (it == _edge_index.end()) {

 	    std::ostringstream msg;

 	    msg << "Edge with label not found: " << tokens[label_index];

 	    throw DataFormatError(msg.str().c_str());	    

 	  }

 	  e = it->second;

 	}

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

 	  _edge_maps[i].second->set(e, tokens[map_index[i]]);

 	}

       }

       if (readSuccess()) {

 	line.putback(c);

       }

     }

     void readAttributes() {

       std::set<std::string> read_attr;

       char c;

       while (readLine() && line >> c && c != '@') {

 	line.putback(c);

 	std::string attr, token;

 	if (!_reader_bits::readToken(line, attr))

 	  throw DataFormatError("Attribute name not found");

 	if (!_reader_bits::readToken(line, token))

 	  throw DataFormatError("Attribute value not found");

 	if (line >> c)

 	  throw DataFormatError("Extra character on the end of line");	  

 	{

 	  std::set<std::string>::iterator it = read_attr.find(attr);

 	  if (it != read_attr.end()) {

 	    std::ostringstream msg;

 	    msg << "Multiple occurence of attribute " << attr;

 	    throw DataFormatError(msg.str().c_str());

 	  }

 	  read_attr.insert(attr);

 	}

 	{

 	  typename Attributes::iterator it = _attributes.lower_bound(attr);

 	  while (it != _attributes.end() && it->first == attr) {

 	    it->second->set(token);

 	    ++it;

 	  }

 	}

       }

       if (readSuccess()) {

 	line.putback(c);

       }

       for (typename Attributes::iterator it = _attributes.begin();

 	   it != _attributes.end(); ++it) {

 	if (read_attr.find(it->first) == read_attr.end()) {

 	  std::ostringstream msg;

 	  msg << "Attribute not found in file: " << it->first;

 	  throw DataFormatError(msg.str().c_str());

 	}	

       }

     }

   public:

     /// \name Execution of the reader    

     /// @{

     /// \brief Start the batch processing

     ///

     /// This function starts the batch processing

     void run() {

       LEMON_ASSERT(_is != 0, "This reader assigned to an other reader");

       bool nodes_done = false;

       bool edges_done = false;

       bool attributes_done = false;

       std::set<std::string> extra_sections;

       line_num = 0;      

       readLine();

       while (readSuccess()) {

 	skipSection();

 	try {

 	  char c;

 	  std::string section, caption;

 	  line >> c;

 	  _reader_bits::readToken(line, section);

 	  _reader_bits::readToken(line, caption);

 	  if (line >> c) 

 	    throw DataFormatError("Extra character on the end of line");

 	  if (section == "nodes" && !nodes_done) {

 	    if (_nodes_caption.empty() || _nodes_caption == caption) {

 	      readNodes();

 	      nodes_done = true;

 	    }

 	  } else if ((section == "edges" || section == "arcs") && 

 		     !edges_done) {

 	    if (_edges_caption.empty() || _edges_caption == caption) {

 	      readEdges();

 	      edges_done = true;

 	    }

 	  } else if (section == "attributes" && !attributes_done) {

 	    if (_attributes_caption.empty() || _attributes_caption == caption) {

 	      readAttributes();

 	      attributes_done = true;

 	    }

 	  } else {

 	    if (extra_sections.find(section) != extra_sections.end()) {

 	      std::ostringstream msg;

 	      msg << "Multiple occurence of section " << section;

 	      throw DataFormatError(msg.str().c_str());

 	    }

 	    Sections::iterator it = _sections.find(section);

 	    if (it != _sections.end()) {

 	      extra_sections.insert(section);

 	      it->second->process(*_is, line_num);

 	      readLine();

 	    } else {

 	      readLine();

 	      skipSection();

 	    }

 	  }

 	} catch (DataFormatError& error) {

 	  error.line(line_num);

 	  throw;

 	}	

       }

       if (!nodes_done) {

 	throw DataFormatError("Section @nodes not found");

       }

       if (!edges_done) {

 	throw DataFormatError("Section @edges not found");

       }

       if (!attributes_done && !_attributes.empty()) {

 	throw DataFormatError("Section @attributes not found");

       }

     }

     /// @}

   };

   /// \relates GraphReader

   template <typename Graph>

   GraphReader<Graph> graphReader(std::istream& is, Graph& graph) {

     GraphReader<Graph> tmp(is, graph);

     return tmp;

   }

   /// \relates GraphReader

   template <typename Graph>

   GraphReader<Graph> graphReader(const std::string& fn, 

 				       Graph& graph) {

     GraphReader<Graph> tmp(fn, graph);

     return tmp;

   }

   /// \relates GraphReader

   template <typename Graph>

   GraphReader<Graph> graphReader(const char* fn, Graph& graph) {

     GraphReader<Graph> tmp(fn, graph);

     return tmp;

   }