/* -*- C++ -*-

  *

  * This file is a part of LEMON, a generic C++ optimization library

  *

  * Copyright (C) 2003-2007

  * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

  * (Egervary Research Group on Combinatorial Optimization, EGRES).

  *

  * Permission to use, modify and distribute this software is granted

  * provided that this copyright notice appears in all copies. For

  * precise terms see the accompanying LICENSE file.

  *

  * This software is provided "AS IS" with no warranty of any kind,

  * express or implied, and with no claim as to its suitability for any

  * purpose.

  *

  */

 ///\ingroup lemon_io

 ///\file

 ///\brief Lemon Format reader.

 #ifndef LEMON_LEMON_READER_H

 #define LEMON_LEMON_READER_H

 #include <iostream>

 #include <fstream>

 #include <string>

 #include <vector>

 #include <algorithm>

 #include <map>

 #include <memory>

 #include <lemon/error.h>

 #include <lemon/graph_utils.h>

 #include <lemon/bits/utility.h>

 #include <lemon/bits/item_reader.h>

 #include <lemon/dim2.h>

 #include <lemon/concept_check.h>

 #include <lemon/concepts/maps.h>

 namespace lemon {

   namespace _reader_bits {

     template <typename T>

     bool operator<(T, T) {

       throw DataFormatError("Label is not comparable");

     }

     template <typename T>

     struct Less {

       bool operator()(const T& p, const T& q) const {

 	return p < q;

       }

     };

     template <typename Item>

     class ItemLabelReader {

     public:

       bool isLabelReader() { return true; }

       void readLabel(std::istream&, Item&) {}

       template <class _ItemLabelReader>

       struct Constraints {

 	void constraints() {

 	  bool b = reader.isLabelReader();

 	  ignore_unused_variable_warning(b);

 	  Item item;

 	  reader.readLabel(is, item);

 	}

 	_ItemLabelReader& reader;

 	std::istream& is;

       };

     };

     template <typename Item>

     class ItemReader {

     public:

       void read(std::istream&, Item&) {}

       template <class _ItemReader>

       struct Constraints {

 	void constraints() {

 	  Item item;

 	  reader.read(is, item);

 	}

 	_ItemReader& reader;

 	std::istream& is;

       };

     };

     template <typename Map>

     struct Ref { typedef Map& Type; };

     template <typename Map>

     struct Arg { typedef Map& Type; };

     template <typename Graph, typename Map>

     class ForwardComposeMap {

     public:

       typedef typename Graph::UEdge Key;

       typedef typename Map::Value Value;

       ForwardComposeMap(const Graph& _graph, typename Arg<Map>::Type _map) 

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

       void set(const Key& key, const Value& val) {

 	map.set(graph.direct(key, true), val);

       }

     private:

       const Graph& graph;

       typename Ref<Map>::Type map;

     };

     template <typename Graph, typename Map>

     ForwardComposeMap<Graph, Map>

     forwardComposeMap(const Graph& graph, const Map& map) {

       return ForwardComposeMap<Graph, Map>(graph, map);

     }

     template <typename Graph, typename Map>

     ForwardComposeMap<Graph, Map>

     forwardComposeMap(const Graph& graph, Map& map) {

       return ForwardComposeMap<Graph, Map>(graph, map);

     }

     template <typename Graph, typename Map>

     class BackwardComposeMap {

     public:

       typedef typename Graph::UEdge Key;

       typedef typename Map::Value Value;

       BackwardComposeMap(const Graph& _graph, typename Arg<Map>::Type _map) 

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

       void set(const Key& key, const Value& val) {

 	map.set(graph.direct(key, false), val);

       }

     private:

       const Graph& graph;

       typename Ref<Map>::Type map;

     };

     template <typename Graph, typename Map>

     BackwardComposeMap<Graph, Map>

     backwardComposeMap(const Graph& graph, const Map& map) {

       return BackwardComposeMap<Graph, Map>(graph, map);

     }

     template <typename Graph, typename Map>

     BackwardComposeMap<Graph, Map>

     backwardComposeMap(const Graph& graph, Map& map) {

       return BackwardComposeMap<Graph, Map>(graph, map);

     }

     template <typename Graph, typename Map>

     struct Ref<ForwardComposeMap<Graph, Map> > { 

       typedef ForwardComposeMap<Graph, Map> Type;

     };

     template <typename Graph, typename Map>

     struct Arg<ForwardComposeMap<Graph, Map> > { 

       typedef const ForwardComposeMap<Graph, Map>& Type;

     };

     template <typename Graph, typename Map>

     struct Ref<BackwardComposeMap<Graph, Map> > { 

       typedef BackwardComposeMap<Graph, Map> Type; 

     };

     template <typename Graph, typename Map>

     struct Arg<BackwardComposeMap<Graph, Map> > { 

       typedef const BackwardComposeMap<Graph, Map>& Type; 

     };

     template <typename Map>

     struct Ref<dim2::XMap<Map> > { 

       typedef dim2::XMap<Map> Type;

     };

     template <typename Map>

     struct Arg<dim2::XMap<Map> > { 

       typedef const dim2::XMap<Map>& Type;

     };

     template <typename Map>

     struct Ref<dim2::YMap<Map> > { 

       typedef dim2::YMap<Map> Type;

     };

     template <typename Map>

     struct Arg<dim2::YMap<Map> > { 

       typedef const dim2::YMap<Map>& Type;

     };

     template <typename _Item>

     class MapReaderBase;

     template <typename _Item>

     class MapInverterBase : public MapReaderBase<_Item> {

     public:

       typedef _Item Item;

       virtual void read(std::istream&, const Item&) = 0;

       virtual Item read(std::istream&) const = 0;

       virtual MapInverterBase<_Item>* getInverter() {

 	return this;

       }

     };

     template <typename _Item, typename _Map, typename _Reader>

     class MapReaderInverter : public MapInverterBase<_Item> {

     public:

       typedef _Item Item;

       typedef _Reader Reader;

       typedef typename Reader::Value Value;

       typedef _Map Map;

       typedef std::map<Value, Item, _reader_bits::Less<Value> > Inverse;

       typename _reader_bits::Ref<Map>::Type map;

       Reader reader;

       Inverse inverse;

       MapReaderInverter(typename _reader_bits::Arg<Map>::Type _map,

 			const Reader& _reader) 

 	: map(_map), reader(_reader) {}

       virtual ~MapReaderInverter() {}

       virtual void read(std::istream& is, const Item& item) {

 	Value value;

 	reader.read(is, value);

 	map.set(item, value);

 	typename Inverse::iterator it = inverse.find(value);

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

 	  inverse.insert(std::make_pair(value, item));

 	} else {

 	  throw DataFormatError("Multiple label occurence");

 	}

       }

       virtual Item read(std::istream& is) const {

 	Value value;

 	reader.read(is, value);	

 	typename Inverse::const_iterator it = inverse.find(value);

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

 	  return it->second;

 	} else {

 	  ErrorMessage msg;

 	  msg << "Invalid label error"; 

 	  throw DataFormatError(msg.message());

 	}

       }      

     };

     template <typename _Item, typename _Reader>

     class SkipReaderInverter : public MapInverterBase<_Item> {

     public:

       typedef _Item Item;

       typedef _Reader Reader;

       typedef typename Reader::Value Value;

       typedef std::map<Value, Item, _reader_bits::Less<Value> > Inverse;

       Reader reader;

       SkipReaderInverter(const Reader& _reader) 

 	: reader(_reader) {}

       virtual ~SkipReaderInverter() {}

       virtual void read(std::istream& is, const Item& item) {

 	Value value;

 	reader.read(is, value);

 	typename Inverse::iterator it = inverse.find(value);

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

 	  inverse.insert(std::make_pair(value, item));

 	} else {

 	  throw DataFormatError("Multiple label occurence error");

 	}

       }

       virtual Item read(std::istream& is) const {

 	Value value;

 	reader.read(is, value);

 	typename Inverse::const_iterator it = inverse.find(value);

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

 	  return it->second;

 	} else {

 	  ErrorMessage msg;

 	  msg << "Invalid label error: " << value; 

 	  throw DataFormatError(msg.message());

 	}

       }

     private:

       Inverse inverse;

     };

     template <typename _Item>    

     class MapReaderBase {

     public:

       typedef _Item Item;

       MapReaderBase() { _touched = false; }

       void touch(bool value = true) { _touched = value; }

       bool touched() const { return _touched; }

       virtual ~MapReaderBase() {}

       virtual void read(std::istream& is, const Item& item) = 0;

       virtual MapInverterBase<_Item>* getInverter() = 0;

     private:      

       bool _touched;

     };

     template <typename _Item, typename _Map, typename _Reader>

     class MapReader : public MapReaderBase<_Item> {

     public:

       typedef _Map Map;

       typedef _Reader Reader;

       typedef typename Reader::Value Value;

       typedef _Item Item;

       typename _reader_bits::Ref<Map>::Type map;

       Reader reader;

       MapReader(typename _reader_bits::Arg<Map>::Type _map, 

 		const Reader& _reader) 

 	: map(_map), reader(_reader) {}

       virtual ~MapReader() {}

       virtual void read(std::istream& is, const Item& item) {

 	Value value;

 	reader.read(is, value);

 	map.set(item, value);

       }

       virtual MapInverterBase<_Item>* getInverter() {

 	return new MapReaderInverter<Item, Map, Reader>(map, reader);

       }

     };

     template <typename _Item, typename _Reader>

     class SkipReader : public MapReaderBase<_Item> {

     public:

       typedef _Reader Reader;

       typedef typename Reader::Value Value;

       typedef _Item Item;

       Reader reader;

       SkipReader(const Reader& _reader) : reader(_reader) {}

       virtual ~SkipReader() {}

       virtual void read(std::istream& is, const Item&) {

 	Value value;

 	reader.read(is, value);

       }      

       virtual MapInverterBase<Item>* getInverter() {

 	return new SkipReaderInverter<Item, Reader>(reader);

       }

     };

     template <typename _Item>

     class LabelReaderBase {

     public:

       typedef _Item Item;

       virtual ~LabelReaderBase() {}

       virtual Item read(std::istream& is) const = 0;

       virtual bool isLabelReader() const = 0;

       virtual LabelReaderBase<_Item>* clone() const = 0;

     };

     template <typename _Item, typename _BoxedLabelReader>

     class LabelReader : public LabelReaderBase<_Item> {

     public:

       typedef _Item Item;

       typedef _BoxedLabelReader BoxedLabelReader;

       const BoxedLabelReader& labelReader;

       LabelReader(const BoxedLabelReader& _labelReader) 

 	: labelReader(_labelReader) {}

       virtual Item read(std::istream& is) const {

 	Item item;

 	labelReader.readLabel(is, item);

 	return item;

       }

       virtual bool isLabelReader() const {

 	return labelReader.isLabelReader();

       }

       LabelReader<Item, BoxedLabelReader>* clone() const {

 	return new LabelReader<Item, BoxedLabelReader>(labelReader);

       }

     };

     template <typename _Item>

     class ItemStore {

     public:

       typedef _Item Item;

       ItemStore(Item& _item) : item(&_item) { 

 	_touched = false; 

       }

       void touch() { _touched = true; }

       bool touched() const { return _touched; }

       void read(const Item& _item) {

 	*item = _item;

       }

     private:

       Item* item;

       bool _touched;

     };

     class ValueReaderBase {

     public:

       virtual void read(std::istream&) {};

       ValueReaderBase() { _touched = false; }

       void touch() { _touched = true; }

       bool touched() const { return _touched; }

       virtual ~ValueReaderBase() {}

     private:

       bool _touched;

     };

     template <typename _Value, typename _Reader>

     class ValueReader : public ValueReaderBase {

     public:

       typedef _Value Value;

       typedef _Reader Reader;

       ValueReader(Value& _value, const Reader& _reader)

  	: value(_value), reader(_reader) {}

       virtual void read(std::istream& is) {

 	reader.read(is, value);

       }

     private:

       Value& value;

       Reader reader;

     };

   }

   /// \ingroup lemon_io

   /// \brief Lemon Format reader class.

   /// 

   /// The Lemon Format contains several sections. We do not want to

   /// determine what sections are in a lemon file we give only a framework

   /// to read a section oriented format.

   ///

   /// In the Lemon Format each section starts with a line containing a

   /// \c \@ character on the first not white space position. This line

   /// is the header line of the section. Each of the next lines belong

   /// to this section until a line starting with \c \@ character is

   /// found. This line can start a new section or it can close the

   /// file with the \c \@end line.  The file format ignores the empty

   /// and comment lines. The line is comment line if it starts with a

   /// \c # character.

   ///

   /// The framework provides an abstract LemonReader::SectionReader class

   /// that defines the interface of a SectionReader. The SectionReader

   /// has the \c header() member function that gets a header line string and

   /// decides if it wants to process the next section. Several SectionReaders

   /// can be attached to a LemonReader and the first attached that can

   /// process the section will be used. Its \c read() member will be called

   /// with a stream containing the section. From this stream the empty and

   /// comment lines are filtered out.

   ///

   /// \relates GraphReader

   /// \relates NodeSetReader

   /// \relates EdgeSetReader

   /// \relates NodesReader

   /// \relates EdgesReader

   /// \relates AttributeReader

   class LemonReader {

   private:

     class FilterStreamBuf : public std::streambuf {

     public:

       typedef std::streambuf Parent;

       typedef Parent::char_type char_type;

       FilterStreamBuf(std::istream& is, int& num) 

 	: _is(is), _base(0), _eptr(0), 

 	  _num(num), skip_state(after_endl) {}

     protected:

       enum skip_state_type {

 	no_skip,

 	after_endl,

 	comment_line

       };

       char_type small_buf[1];

       std::istream& _is;

       char_type* _base;

       char_type* _eptr;

       int& _num;

       skip_state_type skip_state;

       char_type* base() { return _base; }

       char_type* eptr() { return _eptr; }

       int_type blen() { return _eptr - _base; }

       void setb(char_type* buf, int_type len) {

 	_base = buf;

 	_eptr = buf + len;

       }

       virtual std::streambuf* setbuf(char *buf, std::streamsize len) {

 	if (base()) return 0;

 	if (buf != 0 && len >= int(sizeof(small_buf))) {

 	  setb(buf, len);

 	} else {

 	  setb(small_buf, sizeof(small_buf));

 	}

 	setg(0, 0, 0);

 	return this;

       }

       bool put_char(char c) {

 	switch (skip_state) {

 	case no_skip:

 	  switch (c) {

 	  case '\n': 

 	    skip_state = after_endl;

 	    return true;

 	  default:

 	    return true;

 	  }

 	case after_endl:

 	  switch (c) {

 	  case '@':

 	    return false;

 	  case '\n': 

 	    return false;

 	  case '#':

 	    skip_state = comment_line;

 	    return false;

 	  default:

 	    if (!isspace(c)) {

 	      skip_state = no_skip;

 	      return true;

 	    } else {

 	      return false;

 	    }

 	  }

 	  break;

 	case comment_line:

 	  switch (c) {

 	  case '\n': 

 	    skip_state = after_endl;

 	    return false;

 	  default:

 	    return false;

 	  }

 	}

 	return false;

       }

       virtual int_type underflow() {

 	char c;

 	if ((c = _is.peek()) != EOF) {

 	  if (c == '@') {

 	    return EOF;

 	  }

 	} else {

 	  return EOF;

 	}

 	char_type *ptr;

 	for (ptr = base(); ptr != eptr(); ++ptr) {

 	  if ((c = _is.get()) != EOF) {

 	    if (c == '\n') ++_num;

 	    if (put_char(c)) {

 	      *ptr = c;

 	    } else {

 	      if (skip_state == after_endl && c == '@') {

 		_is.putback(c);

 		break;

 	      }

 	      --ptr;

 	    }

 	  } else {

 	    break;

 	  }

 	}

 	setg(base(), base(), ptr);

 	return *base();

       }

       virtual int_type sync() {

 	return EOF;

       }

     public:

       int line_num() const {

 	int r = _num;

 	for (char_type* p = gptr(); p != egptr(); ++p) {

 	  if (*p == '\n') --r;

 	}

 	return r;

       }

     };

     static void skipPreSection(std::istream& is, int& line_num) {

       enum skip_state_type { skip, after_endl };

       skip_state_type skip_state = after_endl;

       char c;

       while ((c = is.get()) != EOF) {

 	if (c == '\n') ++line_num;

 	switch (skip_state) {

 	case skip:

 	  if (c == '\n') skip_state = after_endl;

 	  break;

 	case after_endl:

 	  switch (c) {

 	  case '@':

 	    is.putback(c);

 	    return;

 	  case '\n':

 	    continue;

 	  default:

 	    if (!isspace(c)) {

 	      skip_state = skip;

 	    }

 	    break;

 	  }

 	}	

       }

     }

   public:

     /// \brief Abstract base class for reading a section.

     ///

     /// This class has an \c header() member function what get a 

     /// header line string and decides if it want to process the next 

     /// section. Several SectionReaders can be attached to an LemonReader 

     /// and the first attached what can process the section will be used. 

     /// Its \c read() member will called with a stream contains the section. 

     /// From this stream the empty lines and comments are filtered out.

     class SectionReader {

       friend class LemonReader;

     protected:

       /// \brief Constructor for SectionReader.

       ///

       /// Constructor for SectionReader. It attach this reader to

       /// the given LemonReader.

       SectionReader(LemonReader& reader) {

 	reader.attach(*this);

       }

       virtual ~SectionReader() {}

       /// \brief Gives back true when the SectionReader can process 

       /// the section with the given header line.

       ///

       /// It gives back true when the SectionReader can process

       /// the section with the given header line.

       virtual bool header(const std::string& line) = 0;

       /// \brief Reader function of the section.

       ///

       /// It reads the content of the section.

       virtual void read(std::istream& is) = 0;

       /// \brief The given section missing in the file.

       ///

       /// The given section missing in the file.

       virtual void missing() {};

     };

     /// \brief Constructor for LemonReader.

     ///

     /// Constructor for LemonReader which reads from the given stream.

     LemonReader(std::istream& _is) 

       : is(&_is), own_is(false) {}

     /// \brief Constructor for LemonReader.

     ///

     /// Constructor for LemonReader which reads from the given file.

     LemonReader(const std::string& filename) 

       : is(0), own_is(true) {

       is = new std::ifstream(filename.c_str());

       if (is->fail()) {

 	throw FileOpenError(filename);

       }

     }

     /// \brief Desctructor for LemonReader.

     ///

     /// Desctructor for LemonReader.

     ~LemonReader() {

       if (own_is) {

 	delete is;

       }

     }

   private:

     LemonReader(const LemonReader&);

     void operator=(const LemonReader&);

     void attach(SectionReader& reader) {

       readers.push_back(std::make_pair(&reader, false));

     }

   public:

     /// \brief Executes the LemonReader.

     /// 

     /// It executes the LemonReader.

     void run() {

       int line_num = 0;

       std::string line;

       SectionReaders::iterator it;

       skipPreSection(*is, line_num);

       while ((++line_num, getline(*is, line)) && line.find("@end") != 0) {

 	for (it = readers.begin(); it != readers.end(); ++it) {

 	  if (it->first->header(line)) {

 	    it->second = true;

 	    char buf[2048];

 	    FilterStreamBuf buffer(*is, line_num);

 	    try {

 	      buffer.pubsetbuf(buf, sizeof(buf));

 	      std::istream ss(&buffer);

 	      it->first->read(ss);

 	      skipPreSection(*is, line_num);

 	      break;

 	    } catch (DataFormatError& error) {

 	      error.line(buffer.line_num());

 	      throw;

 	    }	

 	  }

 	}

       }

       for (it = readers.begin(); it != readers.end(); ++it) {

 	if (!it->second) {

 	  try {

 	    it->first->missing();

 	  } catch (DataFormatError& error) {

 	    error.line(line_num);

 	    throw;

 	  }	

 	}

       }

     }

   private:

     std::istream* is;

     bool own_is;

     typedef std::vector<std::pair<SectionReader*, bool> > SectionReaders;

     SectionReaders readers;

   };

   /// \ingroup section_io

   /// \brief SectionReader for reading a graph's nodeset.

   ///

   /// The lemon format can store multiple graph nodesets with several

   /// maps.  The nodeset section's header line is \c \@nodeset \c

   /// nodeset_name, but the \c nodeset_name may be empty.

   ///

   /// The first line of the section contains the names of the maps separated

   /// with white spaces. Each next lines describes a node in the nodeset, and

   /// contains the mapped values for each map.

   ///

   /// If the nodeset contains an \c "label" named map then it will be regarded

   /// as id map. This map should contain only unique values and when the 

   /// \c readLabel() member will read a value from the given stream it will

   /// give back that node which is mapped to this value.

   ///

   /// \relates LemonReader

   template <typename _Graph, typename _Traits = DefaultReaderTraits>

   class NodeSetReader : public LemonReader::SectionReader {

     typedef LemonReader::SectionReader Parent;

   public:

     typedef _Graph Graph;

     typedef _Traits Traits;

     typedef typename Graph::Node Node;

     typedef typename Traits::Skipper DefaultSkipper;

     /// \brief Constructor.

     ///

     /// Constructor for NodeSetReader. It creates the NodeSetReader and

     /// attach it into the given LemonReader. The nodeset reader will

     /// add the read nodes to the given Graph. The reader will read

     /// the section when the \c section_name and the \c _name are the same. 

     NodeSetReader(LemonReader& _reader, 

 		  Graph& _graph, 

 		  const std::string& _name = std::string(),

 		  const DefaultSkipper& _skipper = DefaultSkipper()) 

       : Parent(_reader), graph(_graph), name(_name), skipper(_skipper) {} 

     /// \brief Destructor.

     ///

     /// Destructor for NodeSetReader.

     virtual ~NodeSetReader() {

       for (typename MapReaders::iterator it = readers.begin(); 

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

 	delete it->second;

       }

     }

   private:

     NodeSetReader(const NodeSetReader&);

     void operator=(const NodeSetReader&);

   public:

     /// \brief Add a new node map reader command for the reader.

     ///

     /// Add a new node map reader command for the reader.

     template <typename Map>

     NodeSetReader& readNodeMap(std::string label, Map& map) {

       return _readMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename _reader_bits::Arg<Map>::Type>(label, map);

     }

     template <typename Map>

     NodeSetReader& readNodeMap(std::string label, const Map& map) {

       return _readMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename _reader_bits::Arg<Map>::Type>(label, map);

     }

     /// \brief Add a new node map reader command for the reader.

     ///

     /// Add a new node map reader command for the reader.

     template <typename ItemReader, typename Map>

     NodeSetReader& readNodeMap(std::string label, Map& map, 

 			       const ItemReader& ir = ItemReader()) {

       return _readMap<ItemReader, Map, typename _reader_bits::Arg<Map>::Type>

 	(label, map, ir);

     }

     template <typename ItemReader, typename Map>

     NodeSetReader& readNodeMap(std::string label, const Map& map, 

 			       const ItemReader& ir = ItemReader()) {

       return _readMap<ItemReader, Map, typename _reader_bits::Arg<Map>::Type>

 	(label, map, ir);

     }

   private:

     template <typename ItemReader, typename Map, typename MapParameter>

     NodeSetReader& _readMap(std::string label, MapParameter map, 

 			    const ItemReader& ir = ItemReader()) {

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

       checkConcept<_reader_bits::ItemReader<typename Map::Value>, ItemReader>();

       if (readers.find(label) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for node map: " << label;

 	throw IoParameterError(msg.message());

       }      

       readers.insert(

         make_pair(label, new _reader_bits::

 		  MapReader<Node, Map, ItemReader>(map, ir)));

       return *this;

     }

   public:

     /// \brief Add a new node map skipper command for the reader.

     ///

     /// Add a new node map skipper command for the reader.

     template <typename ItemReader>

     NodeSetReader& skipNodeMap(std::string label, 

                                const ItemReader& ir = ItemReader()) {

       if (readers.find(label) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for node map: " << label;

 	throw IoParameterError(msg.message());

       }

       readers.insert(make_pair(label, new _reader_bits::

 			       SkipReader<Node, ItemReader>(ir)));

       return *this;

     }

   protected:

     /// \brief Gives back true when the SectionReader can process 

     /// the section with the given header line.

     ///

     /// It gives back true when the header line starts with \c \@nodeset,

     /// and the header line's name and the nodeset's name are the same.

     virtual bool header(const std::string& line) {

       std::istringstream ls(line);

       std::string command;

       std::string id;

       ls >> command >> id;

       return command == "@nodeset" && name == id;

     }

     /// \brief Reader function of the section.

     ///

     /// It reads the content of the section.

     virtual void read(std::istream& is) {

       std::vector<_reader_bits::MapReaderBase<Node>* > index;

       std::string line;

       {

         getline(is, line);

         std::istringstream ls(line);

         std::string id;

         while (ls >> id) {

           typename MapReaders::iterator it = readers.find(id);

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

             it->second->touch();

             index.push_back(it->second);

           } else {

             index.push_back(&skipper);

           }

           if (id == "label") {

             inverter.reset(index.back()->getInverter());

             index.back() = inverter.get();

           }

         }

       }

       for (typename MapReaders::iterator it = readers.begin();

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

 	if (!it->second->touched()) {

 	  ErrorMessage msg;

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

 	  throw IoParameterError(msg.message());

 	}

       }

       while (getline(is, line)) {	

 	Node node = graph.addNode();

 	std::istringstream ls(line);

 	for (int i = 0; i < int(index.size()); ++i) {

 	  index[i]->read(ls, node);

 	}

       }

     }

     virtual void missing() {

       if (readers.empty()) return;

       ErrorMessage msg;

       msg << "NodeSet section not found in file: @nodeset " << name;

       throw IoParameterError(msg.message());

     }

   public:

     /// \brief Returns true if the nodeset can give back the node by its label.

     ///

     /// Returns true if the nodeset can give back the node by its label.

     /// It is possible only if an "label" named map was read.

     bool isLabelReader() const {

       return inverter.get() != 0;

     }

     /// \brief Gives back the node by its label.

     ///

     /// It reads an id from the stream and gives back which node belongs to

     /// it. It is possible only if there was read an "label" named map.

     void readLabel(std::istream& is, Node& node) const {

       node = inverter->read(is);

     } 

   private:

     typedef std::map<std::string, _reader_bits::MapReaderBase<Node>*> MapReaders;

     MapReaders readers;

     Graph& graph;   

     std::string name;

     _reader_bits::SkipReader<Node, DefaultSkipper> skipper;

     std::auto_ptr<_reader_bits::MapInverterBase<Node> > inverter;

   };

   /// \ingroup section_io

   /// \brief SectionReader for reading a bipartite graph's nodeset.

   ///

   /// The lemon format can store multiple bipartite graph nodesets

   /// with several maps. The bipartite graph nodeset section's header

   /// line is \c \@bpnodeset \c bpnodeset_name, but the \c bpnodeset_name

   /// may be empty.

   ///

   /// The first line of the section contains \c "&anodeset" and the

   /// the names of the A-node maps and regular maps separated with

   /// white spaces. Each next lines describes an A-node in the anodeset,

   /// and contains the mapped values for each map. If one of the line

   /// starts with \c "&bnodeset" then this line contains the names of

   /// the B-node maps and the regular node maps. And the remaining lines

   /// contains the mapped values to the B-nodes.

   ///

   /// If there is "label" named map then it should be defined in both

   /// nodeset, and it will be regarded as id map. This map should

   /// contain only unique values and when the \c readLabel() member

   /// will read a value from the given stream it will give back that

   /// node which is mapped to this value.

   ///

   /// \relates LemonReader

   template <typename _Graph, typename _Traits = DefaultReaderTraits>

   class BpNodeSetReader : public LemonReader::SectionReader {

     typedef LemonReader::SectionReader Parent;

   public:

     typedef _Graph Graph;

     typedef _Traits Traits;

     typedef typename Graph::Node Node;

     typedef typename Traits::Skipper DefaultSkipper;

     /// \brief Constructor.

     ///

     /// Constructor for BpNodeSetReader. It creates the BpNodeSetReader and

     /// attach it into the given LemonReader. The nodeset reader will

     /// add the read nodes to the given Graph. The reader will read

     /// the section when the \c section_name and the \c _name are the same. 

     BpNodeSetReader(LemonReader& _reader, 

 		  Graph& _graph, 

 		  const std::string& _name = std::string(),

 		  const DefaultSkipper& _skipper = DefaultSkipper()) 

       : Parent(_reader), graph(_graph), name(_name), skipper(_skipper) {} 

     /// \brief Destructor.

     ///

     /// Destructor for BpNodeSetReader.

     virtual ~BpNodeSetReader() {

       for (typename MapReaders::iterator it = readers.begin(); 

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

 	delete it->second;

       }

     }

   private:

     BpNodeSetReader(const BpNodeSetReader&);

     void operator=(const BpNodeSetReader&);

   public:

     /// \brief Add a new node map reader command for the reader.

     ///

     /// Add a new node map reader command for the reader.

     template <typename Map>

     BpNodeSetReader& readNodeMap(std::string label, Map& map) {

       return _readMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename _reader_bits::Arg<Map>::Type>(label, map);

     }

     template <typename Map>

     BpNodeSetReader& readNodeMap(std::string label, const Map& map) {

       return _readMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename _reader_bits::Arg<Map>::Type>(label, map);

     }

     /// \brief Add a new node map reader command for the reader.

     ///

     /// Add a new node map reader command for the reader.

     template <typename ItemReader, typename Map>

     BpNodeSetReader& readNodeMap(std::string label, Map& map, 

 			       const ItemReader& ir = ItemReader()) {

       return _readMap<ItemReader, Map, typename _reader_bits::Arg<Map>::Type>

 	(label, map, ir);

     }

     template <typename ItemReader, typename Map>

     BpNodeSetReader& readNodeMap(std::string label, const Map& map, 

 			       const ItemReader& ir = ItemReader()) {

       return _readMap<ItemReader, Map, typename _reader_bits::Arg<Map>::Type>

 	(label, map, ir);

     }

   private:

     template <typename ItemReader, typename Map, typename MapParameter>

     BpNodeSetReader& _readMap(std::string label, MapParameter map, 

 			    const ItemReader& ir = ItemReader()) {

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

       checkConcept<_reader_bits::ItemReader<typename Map::Value>, ItemReader>();

       if (areaders.find(label) != areaders.end() ||

 	  breaders.find(label) != breaders.end() ||

 	  readers.find(label) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for node map: " << label;

 	throw IoParameterError(msg.message());

       }      

       readers.insert(make_pair(label, new _reader_bits::

 		  MapReader<Node, Map, ItemReader>(map, ir)));

       return *this;

     }

   public:

     /// \brief Add a new A-node map reader command for the reader.

     ///

     /// Add a new A-node map reader command for the reader.

     template <typename Map>

     BpNodeSetReader& readANodeMap(std::string label, Map& map) {

       return _readAMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename _reader_bits::Arg<Map>::Type>(label, map);

     }

     template <typename Map>

     BpNodeSetReader& readANodeMap(std::string label, const Map& map) {

       return _readAMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename _reader_bits::Arg<Map>::Type>(label, map);

     }

     /// \brief Add a new A-node map reader command for the reader.

     ///

     /// Add a new A-node map reader command for the reader.

     template <typename ItemReader, typename Map>

     BpNodeSetReader& readANodeMap(std::string label, Map& map, 

 			       const ItemReader& ir = ItemReader()) {

       return _readAMap<ItemReader, Map, typename _reader_bits::Arg<Map>::Type>

 	(label, map, ir);

     }

     template <typename ItemReader, typename Map>

     BpNodeSetReader& readANodeMap(std::string label, const Map& map, 

 			       const ItemReader& ir = ItemReader()) {

       return _readAMap<ItemReader, Map, typename _reader_bits::Arg<Map>::Type>

 	(label, map, ir);

     }

   private:

     template <typename ItemReader, typename Map, typename MapParameter>

     BpNodeSetReader& _readAMap(std::string label, MapParameter map, 

 			    const ItemReader& ir = ItemReader()) {

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

       checkConcept<_reader_bits::ItemReader<typename Map::Value>, ItemReader>();

       if (label == "label") {

 	throw IoParameterError("Label cannot be A-node map");

       }

       if (areaders.find(label) != areaders.end() ||

 	  readers.find(label) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for A-node map: " << label;

 	throw IoParameterError(msg.message());

       }

       areaders.insert(make_pair(label, new _reader_bits::

 				MapReader<Node, Map, ItemReader>(map, ir)));

       return *this;

     }

   public:

     /// \brief Add a new B-node map reader command for the reader.

     ///

     /// Add a new B-node map reader command for the reader.

     template <typename Map>

     BpNodeSetReader& readBNodeMap(std::string label, Map& map) {

       return _readBMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename _reader_bits::Arg<Map>::Type>(label, map);

     }

     template <typename Map>

     BpNodeSetReader& readBNodeMap(std::string label, const Map& map) {

       return _readBMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename _reader_bits::Arg<Map>::Type>(label, map);

     }

     /// \brief Add a new B-node map reader command for the reader.

     ///

     /// Add a new B-node map reader command for the reader.

     template <typename ItemReader, typename Map>

     BpNodeSetReader& readBNodeMap(std::string label, Map& map, 

 			       const ItemReader& ir = ItemReader()) {

       return _readBMap<ItemReader, Map, typename _reader_bits::Arg<Map>::Type>

 	(label, map, ir);

     }

     template <typename ItemReader, typename Map>

     BpNodeSetReader& readBNodeMap(std::string label, const Map& map, 

 			       const ItemReader& ir = ItemReader()) {

       return _readBMap<ItemReader, Map, typename _reader_bits::Arg<Map>::Type>

 	(label, map, ir);

     }

   private:

     template <typename ItemReader, typename Map, typename MapParameter>

     BpNodeSetReader& _readBMap(std::string label, MapParameter map, 

 			    const ItemReader& ir = ItemReader()) {

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

       checkConcept<_reader_bits::ItemReader<typename Map::Value>, ItemReader>();

       if (label == "label") {

 	throw IoParameterError("Label cannot be B-node map");

       }

       if (breaders.find(label) != breaders.end() ||

 	  readers.find(label) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for B-node map: " << label;

 	throw IoParameterError(msg.message());

       }

       breaders.insert(make_pair(label, new _reader_bits::

 				MapReader<Node, Map, ItemReader>(map, ir)));

       return *this;

     }

   public:

     /// \brief Add a new node map skipper command for the reader.

     ///

     /// Add a new node map skipper command for the reader.

     template <typename ItemReader>

     BpNodeSetReader& skipNodeMap(std::string label, 

 				 const ItemReader& ir = ItemReader()) {

       if (areaders.find(label) != areaders.end() ||

 	  breaders.find(label) != breaders.end() ||

 	  readers.find(label) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for node map: " << label;

 	throw IoParameterError(msg.message());

       }

       readers.insert(make_pair(label, new _reader_bits::

 			       SkipReader<Node, ItemReader>(ir)));

       return *this;

     }

     /// \brief Add a new A-node map skipper command for the reader.

     ///

     /// Add a new A-node map skipper command for the reader.

     template <typename ItemReader>

     BpNodeSetReader& skipANodeMap(std::string label, 

 				  const ItemReader& ir = ItemReader()) {

       if (label == "label") {

 	throw IoParameterError("Label cannot be A-node map");

       }

       if (areaders.find(label) != areaders.end() ||

 	  readers.find(label) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for A-node map: " << label;

 	throw IoParameterError(msg.message());

       }

       areaders.insert(make_pair(label, new _reader_bits::

 				SkipReader<Node, ItemReader>(ir)));

       return *this;

     }

     /// \brief Add a new B-node map skipper command for the reader.

     ///

     /// Add a new B-node map skipper command for the reader.

     template <typename ItemReader>

     BpNodeSetReader& skipBNodeMap(std::string label, 

 				  const ItemReader& ir = ItemReader()) {

       if (label == "label") {

 	throw IoParameterError("Label cannot be B-node map");

       }

       if (breaders.find(label) != breaders.end() ||

 	  readers.find(label) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for B-node map: " << label;

 	throw IoParameterError(msg.message());

       }

       breaders.insert(make_pair(label, new _reader_bits::

 				SkipReader<Node, ItemReader>(ir)));

       return *this;

     }

   protected:

     /// \brief Gives back true when the SectionReader can process 

     /// the section with the given header line.

     ///

     /// It gives back true when the header line starts with \c \@nodeset,

     /// and the header line's name and the nodeset's name are the same.

     virtual bool header(const std::string& line) {

       std::istringstream ls(line);

       std::string command;

       std::string id;

       ls >> command >> id;

       return command == "@bpnodeset" && name == id;

     }

     /// \brief Reader function of the section.

     ///

     /// It reads the content of the section.

     virtual void read(std::istream& is) {

       std::string line;

       {

 	std::vector<_reader_bits::MapReaderBase<Node>* > index;

 	{

 	  getline(is, line);

 	  std::istringstream ls(line);

 	  std::string id;

 	  ls >> id;

 	  if (id != "&anodeset") {

 	    throw IoParameterError("Cannot find &anodeset subsection");

 	  }

 	  while (ls >> id) {

 	    typename MapReaders::iterator it = readers.find(id);

 	    typename MapReaders::iterator ait = areaders.find(id);

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

 	      it->second->touch();

 	      index.push_back(it->second);

 	    } else if (ait != areaders.end()) {

 	      ait->second->touch();

 	      index.push_back(ait->second);

 	    }

 	    if (id == "label") {

 	      inverter.reset(index.back()->getInverter());

 	      index.back() = inverter.get();

 	    }

 	  }

 	}

 	for (typename MapReaders::iterator it = areaders.begin();

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

 	  if (!it->second->touched()) {

 	    ErrorMessage msg;

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

 	    throw IoParameterError(msg.message());

 	  }

 	}

 	for (typename MapReaders::iterator it = readers.begin();

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

 	  if (!it->second->touched()) {

 	    ErrorMessage msg;

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

 	    throw IoParameterError(msg.message());

 	  }

 	  it->second->touch(false);

 	}

 	while (getline(is, line)) {

 	  if (line[0] == '&') {

 	    std::istringstream ls(line);

 	    std::string id;

 	    ls >> id;

 	    if (id == "&bnodeset") break;

 	  }

 	  Node node = graph.addANode();

 	  std::istringstream ls(line);

 	  for (int i = 0; i < int(index.size()); ++i) {

 	    index[i]->read(ls, node);

 	  }

 	}

       }

       {

 	std::vector<_reader_bits::MapReaderBase<Node>* > index;

 	{

 	  std::istringstream ls(line);

 	  std::string id;

 	  ls >> id;

 	  if (id != "&bnodeset") {

 	    throw IoParameterError("Cannot find &bnodeset subsection");

 	  }

 	  while (ls >> id) {

 	    typename MapReaders::iterator it = readers.find(id);

 	    typename MapReaders::iterator bit = breaders.find(id);

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

 	      it->second->touch();

 	      index.push_back(it->second);

 	    } else if (bit != breaders.end()) {

 	      bit->second->touch();

 	      index.push_back(bit->second);

 	    }

 	    if (id == "label" && inverter.get() != 0) {

 	      index.back() = inverter.get();

 	    }

 	  }

 	}

 	for (typename MapReaders::iterator it = breaders.begin();

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

 	  if (!it->second->touched()) {

 	    ErrorMessage msg;

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

 	    throw IoParameterError(msg.message());

 	  }

 	}

 	for (typename MapReaders::iterator it = readers.begin();

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

 	  if (!it->second->touched()) {

 	    ErrorMessage msg;

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

 	    throw IoParameterError(msg.message());

 	  }

 	}

 	while (getline(is, line)) {	

 	  Node node = graph.addBNode();

 	  std::istringstream ls(line);

 	  for (int i = 0; i < int(index.size()); ++i) {

 	    index[i]->read(ls, node);

 	  }

 	}

       }

     }

     virtual void missing() {

       if (readers.empty()) return;

       ErrorMessage msg;

       msg << "BpNodeSet section not found in file: @bpnodeset " << name;

       throw IoParameterError(msg.message());

     }

   public:

     /// \brief Returns true if the nodeset can give back the node by its label.

     ///

     /// Returns true if the nodeset can give back the node by its label.

     /// It is possible only if an "label" named map was read.

     bool isLabelReader() const {

       return inverter.get() != 0;

     }

     /// \brief Gives back the node by its label.

     ///

     /// It reads an id from the stream and gives back which node belongs to

     /// it. It is possible only if there was read an "label" named map.

     void readLabel(std::istream& is, Node& node) const {

       node = inverter->read(is);

     } 

   private:

     typedef std::map<std::string, _reader_bits::MapReaderBase<Node>*> 

     MapReaders;

     MapReaders areaders, breaders, readers;

     Graph& graph;

     std::string name;

     _reader_bits::SkipReader<Node, DefaultSkipper> skipper;

     std::auto_ptr<_reader_bits::MapInverterBase<Node> > inverter;

   };

   /// \ingroup section_io

   /// \brief SectionReader for reading a graph's edgeset.

   ///

   /// The lemon format can store multiple graph edgesets with several maps.

   /// The edgeset section's header line is \c \@edgeset \c edgeset_name, but the

   /// \c edgeset_name may be empty.

   ///

   /// The first line of the section contains the names of the maps separated

   /// with white spaces. Each next lines describes an edge in the edgeset. The

   /// line contains the source and the target nodes' id and the mapped 

   /// values for each map.

   ///

   /// If the edgeset contains an \c "label" named map then it will be regarded

   /// as id map. This map should contain only unique values and when the 

   /// \c readLabel() member will read a value from the given stream it will

   /// give back that edge which is mapped to this value.

   ///

   /// The edgeset reader needs a node id reader to identify which nodes

   /// have to be connected. If a NodeSetReader reads an "label" named map,

   /// it will be able to resolve the nodes by ids.

   ///

   /// \relates LemonReader

   template <typename _Graph, typename _Traits = DefaultReaderTraits>

   class EdgeSetReader : public LemonReader::SectionReader {

     typedef LemonReader::SectionReader Parent;

   public:

     typedef _Graph Graph;

     typedef _Traits Traits;

     typedef typename Graph::Node Node;

     typedef typename Graph::Edge Edge;

     typedef typename Traits::Skipper DefaultSkipper;

     /// \brief Constructor.

     ///

     /// Constructor for EdgeSetReader. It creates the EdgeSetReader and

     /// attach it into the given LemonReader. The edgeset reader will

     /// add the read edges to the given Graph. It will use the given

     /// node id reader to read the source and target nodes of the edges.

     /// The reader will read the section only if the \c _name and the 

     /// \c edgset_name are the same. 

     template <typename NodeLabelReader>

     EdgeSetReader(LemonReader& _reader, 

 		  Graph& _graph, 

 		  const NodeLabelReader& _nodeLabelReader, 

 		  const std::string& _name = std::string(),

 		  const DefaultSkipper& _skipper = DefaultSkipper()) 

       : Parent(_reader), graph(_graph), name(_name), skipper(_skipper) {

       checkConcept<_reader_bits::ItemLabelReader<Node>, NodeLabelReader>();

       nodeLabelReader.reset(new _reader_bits::

 			 LabelReader<Node, NodeLabelReader>(_nodeLabelReader));

     }

     /// \brief Destructor.

     ///

     /// Destructor for EdgeSetReader.

     virtual ~EdgeSetReader() {

       for (typename MapReaders::iterator it = readers.begin(); 

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

 	delete it->second;

       }

     }

   private:

     EdgeSetReader(const EdgeSetReader&);

     void operator=(const EdgeSetReader&);

   public:

     /// \brief Add a new edge map reader command for the reader.

     ///

     /// Add a new edge map reader command for the reader.

     template <typename Map>

     EdgeSetReader& readEdgeMap(std::string label, Map& map) {

       return _readMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename _reader_bits::Arg<Map>::Type>(label, map);

     }

     template <typename Map>

     EdgeSetReader& readEdgeMap(std::string label, const Map& map) {

       return _readMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename _reader_bits::Arg<Map>::Type>(label, map);

     }

     /// \brief Add a new edge map reader command for the reader.

     ///

     /// Add a new edge map reader command for the reader.

     template <typename ItemReader, typename Map>

     EdgeSetReader& readEdgeMap(std::string label, Map& map, 

                                const ItemReader& ir = ItemReader()) {

       return _readMap<ItemReader, Map,

 	typename _reader_bits::Arg<Map>::Type>(label, map, ir);

     }

     template <typename ItemReader, typename Map>

     EdgeSetReader& readEdgeMap(std::string label, const Map& map, 

 			       const ItemReader& ir = ItemReader()) {

       return _readMap<ItemReader, Map,

 	typename _reader_bits::Arg<Map>::Type>(label, map, ir);

     }

   private:

     template <typename ItemReader, typename Map, typename MapParameter>

     EdgeSetReader& _readMap(std::string label, MapParameter map, 

 			    const ItemReader& ir = ItemReader()) {

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

       checkConcept<_reader_bits::ItemReader<typename Map::Value>, ItemReader>();

       if (readers.find(label) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for edge map: " << label;

 	throw IoParameterError(msg.message());

       }

       readers.insert(

 	make_pair(label, new _reader_bits::

 		  MapReader<Edge, Map, ItemReader>(map, ir)));

       return *this;

     }

   public:

     /// \brief Add a new edge map skipper command for the reader.

     ///

     /// Add a new edge map skipper command for the reader.

     template <typename ItemReader>

     EdgeSetReader& skipEdgeMap(std::string label, 

 			       const ItemReader& ir = ItemReader()) {

       if (readers.find(label) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for edge map: " << label;

 	throw IoParameterError(msg.message());

       }

       readers.insert(make_pair(label, new _reader_bits::

 			       SkipReader<Edge, ItemReader>(ir)));

       return *this;

     }

   protected:

     /// \brief Gives back true when the SectionReader can process 

     /// the section with the given header line.

     ///

     /// It gives back true when the header line starts with \c \@edgeset,

     /// and the header line's name and the edgeset's name are the same.

     /// The sections with \@uedgeset head line could be read with this

     /// section reader too.

     virtual bool header(const std::string& line) {

       std::istringstream ls(line);

       std::string command;

       std::string id;

       ls >> command >> id;

       return (command == "@edgeset" || command == "@uedgeset") && name == id;

     }

     /// \brief Reader function of the section.

     ///

     /// It reads the content of the section.

     virtual void read(std::istream& is) {

       if (!nodeLabelReader->isLabelReader()) {

 	throw DataFormatError("Cannot find nodeset or label map");

       }

       std::vector<_reader_bits::MapReaderBase<Edge>* > index;

       std::string line;

       {

         getline(is, line);

         std::istringstream ls(line);	

         std::string id;

         while (ls >> id) {

           typename MapReaders::iterator it = readers.find(id);

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

             index.push_back(it->second);

             it->second->touch();

           } else {

             index.push_back(&skipper);

           }

           if (id == "label") {

             inverter.reset(index.back()->getInverter());

             index.back() = inverter.get();

           }

         }

       }

       for (typename MapReaders::iterator it = readers.begin();

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

 	if (!it->second->touched()) {

 	  ErrorMessage msg;

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

 	  throw IoParameterError(msg.message());

 	}

       }

       while (getline(is, line)) {	

 	std::istringstream ls(line);

 	Node from = nodeLabelReader->read(ls);

 	Node to = nodeLabelReader->read(ls);

 	Edge edge = graph.addEdge(from, to);

 	for (int i = 0; i < int(index.size()); ++i) {

 	  index[i]->read(ls, edge);

 	}

       }

     }

     virtual void missing() {

       if (readers.empty()) return;

       ErrorMessage msg;

       msg << "EdgeSet section not found in file: @edgeset " << name;

       throw IoParameterError(msg.message());

     }

   public:

     /// \brief Returns true if the edgeset can give back the edge by its label.

     ///

     /// Returns true if the edgeset can give back the edge by its label.

     /// It is possible only if an "label" named map was read.

     bool isLabelReader() const {

       return inverter.get() != 0;

     }

     /// \brief Gives back the edge by its label.

     ///

     /// It reads an id from the stream and gives back which edge belongs to

     /// it. It is possible only if there was read an "label" named map.

     void readLabel(std::istream& is, Edge& edge) const {

       edge = inverter->read(is);

     } 

   private:

     typedef std::map<std::string, _reader_bits::MapReaderBase<Edge>*> 

     MapReaders;

     MapReaders readers;

     Graph& graph;   

     std::string name;

     _reader_bits::SkipReader<Edge, DefaultSkipper> skipper;

     std::auto_ptr<_reader_bits::MapInverterBase<Edge> > inverter;

     std::auto_ptr<_reader_bits::LabelReaderBase<Node> > nodeLabelReader;

   };

   /// \ingroup section_io

   /// \brief SectionReader for reading a undirected graph's edgeset.

   ///

   /// The lemon format can store multiple undirected edgesets with several 

   /// maps. The undirected edgeset section's header line is \c \@uedgeset 

   /// \c uedgeset_name, but the \c uedgeset_name may be empty.

   ///

   /// The first line of the section contains the names of the maps separated

   /// with white spaces. Each next lines describes an edge in the edgeset. The

   /// line contains the connected nodes' id and the mapped values for each map.

   ///

   /// The section can handle the directed as a syntactical sugar. Two

   /// undirected edge map describes one directed edge map. This two maps

   /// are the forward map and the backward map and the names of this map

   /// is near the same just with a prefix \c '+' or \c '-' character 

   /// difference.

   ///

   /// If the edgeset contains an \c "label" named map then it will be regarded

   /// as id map. This map should contain only unique values and when the 

   /// \c readLabel() member will read a value from the given stream it will

   /// give back that uicted edge which is mapped to this value.

   ///

   /// The undirected edgeset reader needs a node id reader to identify which 

   /// nodes have to be connected. If a NodeSetReader reads an "label" named 

   /// map, it will be able to resolve the nodes by ids.

   ///

   /// \relates LemonReader

   template <typename _Graph, typename _Traits = DefaultReaderTraits>

   class UEdgeSetReader : public LemonReader::SectionReader {

     typedef LemonReader::SectionReader Parent;

   public:

     typedef _Graph Graph;

     typedef _Traits Traits;

     typedef typename Graph::Node Node;

     typedef typename Graph::Edge Edge;

     typedef typename Graph::UEdge UEdge;

     typedef typename Traits::Skipper DefaultSkipper;

     /// \brief Constructor.

     ///

     /// Constructor for UEdgeSetReader. It creates the UEdgeSetReader 

     /// and attach it into the given LemonReader. The undirected edgeset 

     /// reader will add the read undirected edges to the given Graph. It 

     /// will use the given node id reader to read the source and target 

     /// nodes of the edges. The reader will read the section only if the 

     /// \c _name and the \c uedgset_name are the same. 

     template <typename NodeLabelReader>

     UEdgeSetReader(LemonReader& _reader, 

 		       Graph& _graph, 

 		       const NodeLabelReader& _nodeLabelReader, 

 		       const std::string& _name = std::string(),

 		       const DefaultSkipper& _skipper = DefaultSkipper()) 

       : Parent(_reader), graph(_graph), name(_name), skipper(_skipper) {

       checkConcept<_reader_bits::ItemLabelReader<Node>, NodeLabelReader>();

       nodeLabelReader.reset(new _reader_bits::

 			 LabelReader<Node, NodeLabelReader>(_nodeLabelReader));

     }

     /// \brief Destructor.

     ///

     /// Destructor for UEdgeSetReader.

     virtual ~UEdgeSetReader() {

       for (typename MapReaders::iterator it = readers.begin(); 

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

 	delete it->second;

       }

     }

   private:

     UEdgeSetReader(const UEdgeSetReader&);

     void operator=(const UEdgeSetReader&);

   public:

     /// \brief Add a new undirected edge map reader command for the reader.

     ///

     /// Add a new edge undirected map reader command for the reader.

     template <typename Map>

     UEdgeSetReader& readUEdgeMap(std::string label, Map& map) {

       return _readMap<

 	typename Traits::template Reader<typename Map::Value>, Map, 

 	typename _reader_bits::Arg<Map>::Type>(label, map);

     }

     template <typename Map>

     UEdgeSetReader& readUEdgeMap(std::string label, const Map& map) {

       return _readMap<

 	typename Traits::template Reader<typename Map::Value>, Map, 

 	typename _reader_bits::Arg<Map>::Type>(label, map);

     }

     /// \brief Add a new undirected edge map reader command for the reader.

     ///

     /// Add a new edge undirected map reader command for the reader.

     template <typename ItemReader, typename Map>

     UEdgeSetReader& readUEdgeMap(std::string label, Map& map, 

                                  const ItemReader& ir = ItemReader()) {

       return _readMap<ItemReader, Map, typename _reader_bits::Arg<Map>::Type>

 	(label, map, ir);

     }

     template <typename ItemReader, typename Map>

     UEdgeSetReader& readUEdgeMap(std::string label, const Map& map, 

                                  const ItemReader& ir = ItemReader()) {

       return _readMap<ItemReader, Map, typename _reader_bits::Arg<Map>::Type >

 	(label, map, ir);

     }

   private:

     template <typename ItemReader, typename Map, typename MapParameter>

     UEdgeSetReader& _readMap(std::string label, MapParameter map,

                              const ItemReader& ir = ItemReader()) {

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

       checkConcept<_reader_bits::ItemReader<typename Map::Value>, ItemReader>();

       if (readers.find(label) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for edge map: " << label;

 	throw IoParameterError(msg.message());

       }

       readers.insert(

 	make_pair(label, new _reader_bits::

 		  MapReader<UEdge, Map, ItemReader>(map, ir)));

       return *this;

     }

   public:

     /// \brief Add a new undirected edge map skipper command for the reader.

     ///

     /// Add a new undirected edge map skipper command for the reader.

     template <typename ItemReader>

     UEdgeSetReader& skipUEdgeMap(std::string label, 

                                  const ItemReader& ir = ItemReader()) {

       if (readers.find(label) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for node map: " << label;

 	throw IoParameterError(msg.message());

       }

       readers.insert(make_pair(label, new _reader_bits::

 			       SkipReader<UEdge, ItemReader>(ir)));

       return *this;

     }

     /// \brief Add a new directed edge map reader command for the reader.

     ///

     /// Add a new directed edge map reader command for the reader.

     template <typename Map>

     UEdgeSetReader& readEdgeMap(std::string label, Map& map) {

       return _readDirMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename _reader_bits::Arg<Map>::Type>(label, map);

     }

     template <typename Map>

     UEdgeSetReader& readEdgeMap(std::string label, const Map& map) {

       return _readDirMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename _reader_bits::Arg<Map>::Type>(label, map);

     }

     /// \brief Add a new directed edge map reader command for the reader.

     ///

     /// Add a new directed edge map reader command for the reader.

     template <typename ItemReader, typename Map>

     UEdgeSetReader& readEdgeMap(std::string label, Map& map, 

 				    const ItemReader& ir = ItemReader()) {

       return _readDirMap<ItemReader, Map, 

         typename _reader_bits::Arg<Map>::Type>(label, map, ir);

     }

     template <typename ItemReader, typename Map>

     UEdgeSetReader& readEdgeMap(std::string label, const Map& map, 

 				    const ItemReader& ir = ItemReader()) {

       return _readDirMap<ItemReader, Map, 

         typename _reader_bits::Arg<Map>::Type>(label, map, ir);

     }

   private:

     template <typename ItemReader, typename Map, typename MapParameter>

     UEdgeSetReader& _readDirMap(std::string label, MapParameter map,

 				    const ItemReader& ir = ItemReader()) { 

       checkConcept<_reader_bits::ItemReader<typename Map::Value>, ItemReader>();

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

       readUEdgeMap("+" + label, 

                    _reader_bits::forwardComposeMap(graph, map), ir);

       readUEdgeMap("-" + label, 

                    _reader_bits::backwardComposeMap(graph, map), ir);

       return *this;      

     }

   public:

     /// \brief Add a new directed edge map skipper command for the reader.

     ///

     /// Add a new directed edge map skipper command for the reader.

     template <typename ItemReader>

     UEdgeSetReader& skipEdgeMap(std::string label, 

                                 const ItemReader& ir = ItemReader()) {

       skipUEdgeMap("+" + label, ir);

       skipUEdgeMap("-" + label, ir);

       return *this;

     }

   protected:

     /// \brief Gives back true when the SectionReader can process 

     /// the section with the given header line.

     ///

     /// It gives back true when the header line starts with \c \@uedgeset,

     /// and the header line's name and the edgeset's name are the same.

     /// The sections with \@edgeset head line could be read with this

     /// section reader too.

     virtual bool header(const std::string& line) {

       std::istringstream ls(line);

       std::string command;

       std::string id;

       ls >> command >> id;

       return (command == "@edgeset" || command == "@uedgeset") && name == id;

     }

     /// \brief Reader function of the section.

     ///

     /// It reads the content of the section.

     virtual void read(std::istream& is) {

       if (!nodeLabelReader->isLabelReader()) {

 	throw DataFormatError("Cannot find nodeset or label map");

       }

       std::vector<_reader_bits::MapReaderBase<UEdge>* > index;

       std::string line;

       {

         getline(is, line);

         std::istringstream ls(line);	

         std::string id;

         while (ls >> id) {

           typename MapReaders::iterator it = readers.find(id);

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

             index.push_back(it->second);

             it->second->touch();

           } else {

             index.push_back(&skipper);

           }

           if (id == "label") {

             inverter.reset(index.back()->getInverter());

             index.back() = inverter.get();

           }

         }

         for (typename MapReaders::iterator it = readers.begin();

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

           if (!it->second->touched()) {

             ErrorMessage msg;

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

             throw IoParameterError(msg.message());

           }

         }

       }

       while (getline(is, line)) {	

 	std::istringstream ls(line);

 	Node from = nodeLabelReader->read(ls);

 	Node to = nodeLabelReader->read(ls);

 	UEdge edge = graph.addEdge(from, to);

 	for (int i = 0; i < int(index.size()); ++i) {

 	  index[i]->read(ls, edge);

 	}

       }

     }

     virtual void missing() {

       if (readers.empty()) return;

       ErrorMessage msg;

       msg << "UEdgeSet section not found in file: @uedgeset " << name;

       throw IoParameterError(msg.message());

     }

   public:

     /// \brief Returns true if the edgeset can give back the edge by its label.

     ///

     /// Returns true if the edgeset can give back the undirected edge by its 

     /// id. It is possible only if an "label" named map was read.

     bool isLabelReader() const {

       return inverter.get() != 0;

     }

     /// \brief Gives back the undirected edge by its label.

     ///

     /// It reads an id from the stream and gives back which undirected edge 

     /// belongs to it. It is possible only if there was read an "label" named map.

     void readLabel(std::istream& is, UEdge& uedge) const {

       uedge = inverter->read(is);

     } 

     /// \brief Gives back the directed edge by its label.

     ///

     /// It reads an id from the stream and gives back which directed edge 

     /// belongs to it. The directed edge id is the \c '+' or \c '-' character

     /// and the undirected edge id. It is possible only if there was read 

     /// an "label" named map.

     void readLabel(std::istream& is, Edge& edge) const {

       char c;

       is >> c;

       UEdge uedge = inverter->read(is);

       if (c == '+') {

 	edge = graph.direct(uedge, true);

       } else if (c == '-') {

         edge = graph.direct(uedge, false);

       } else {

 	throw DataFormatError("Wrong id format for edge "

 			      "in undirected edgeset");

       }

     } 

   private:

     typedef std::map<std::string, 

 		     _reader_bits::MapReaderBase<UEdge>*> MapReaders;

     MapReaders readers;

     Graph& graph;   

     std::string name;

     _reader_bits::SkipReader<UEdge, DefaultSkipper> skipper;

     std::auto_ptr<_reader_bits::MapInverterBase<UEdge> > inverter;

     std::auto_ptr<_reader_bits::LabelReaderBase<Node> > nodeLabelReader;

   };

   /// \ingroup section_io

   /// \brief SectionReader for reading labeled nodes.

   ///

   /// The nodes section's header line is \c \@nodes \c nodes_name, but the

   /// \c nodes_name may be empty.

   ///

   /// Each line in the section contains the name of the node 

   /// and then the node id. 

   ///

   /// \relates LemonReader

   template <typename _Graph>

   class NodeReader : public LemonReader::SectionReader {

     typedef LemonReader::SectionReader Parent;

     typedef _Graph Graph;

     typedef typename Graph::Node Node;

   public:

     /// \brief Constructor.

     ///

     /// Constructor for NodeReader. It creates the NodeReader and

     /// attach it into the given LemonReader. It will use the given

     /// node id reader to give back the nodes. The reader will read the 

     /// section only if the \c _name and the \c nodes_name are the same. 

     template <typename _LabelReader>

     NodeReader(LemonReader& _reader, const _LabelReader& _labelReader, 

 	       const std::string& _name = std::string()) 

       : Parent(_reader), name(_name) {

       checkConcept<_reader_bits::ItemLabelReader<Node>, _LabelReader>();

       nodeLabelReader.reset(new _reader_bits::

 			 LabelReader<Node, _LabelReader>(_labelReader));

     }

     /// \brief Destructor.

     ///

     /// Destructor for NodeReader.

     virtual ~NodeReader() {}

   private:

     NodeReader(const NodeReader&);

     void operator=(const NodeReader&);

   public:

     /// \brief Add a node reader command for the NodeReader.

     ///

     /// Add a node reader command for the NodeReader.

     void readNode(std::string label, Node& item) {

       if (readers.find(label) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for node: " << label;

 	throw IoParameterError(msg.message());

       }

       readers.insert(make_pair(label, _reader_bits::ItemStore<Node>(item)));

     }

   protected:

     /// \brief Gives back true when the SectionReader can process 

     /// the section with the given header line.

     ///

     /// It gives back true when the header line start with \c \@nodes,

     /// and the header line's name and the reader's name are the same.

     virtual bool header(const std::string& line) {

       std::istringstream ls(line);

       std::string command;

       std::string id;

       ls >> command >> id;

       return command == "@nodes" && name == id;

     }

     /// \brief Reader function of the section.

     ///

     /// It reads the content of the section.

     virtual void read(std::istream& is) {

       if (!nodeLabelReader->isLabelReader()) {

 	throw DataFormatError("Cannot find nodeset or label map");

       }

       std::string line;

       while (getline(is, line)) {

 	std::istringstream ls(line);

 	std::string id;

 	ls >> id;

 	typename NodeReaders::iterator it = readers.find(id);

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

 	  it->second.read(nodeLabelReader->read(ls));

 	  it->second.touch();

 	}	

       }

       for (typename NodeReaders::iterator it = readers.begin();

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

 	if (!it->second.touched()) {

 	  ErrorMessage msg;

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

 	  throw IoParameterError(msg.message());

 	}

       }

     }

     virtual void missing() {

       if (readers.empty()) return;

       ErrorMessage msg;

       msg << "Nodes section not found in file: @nodes " << name;

       throw IoParameterError(msg.message());

     }

   private:

     std::string name;

     typedef std::map<std::string, _reader_bits::ItemStore<Node> > NodeReaders;

     NodeReaders readers;

     std::auto_ptr<_reader_bits::LabelReaderBase<Node> > nodeLabelReader;

   };

   /// \ingroup section_io

   /// \brief SectionReader for reading labeled edges.

   ///

   /// The edges section's header line is \c \@edges \c edges_name, but the

   /// \c edges_name may be empty.

   ///

   /// Each line in the section contains the name of the edge 

   /// and then the edge id. 

   ///

   /// \relates LemonReader

   template <typename _Graph>

   class EdgeReader : public LemonReader::SectionReader {

     typedef LemonReader::SectionReader Parent;

     typedef _Graph Graph;

     typedef typename Graph::Edge Edge;

   public:

     /// \brief Constructor.

     ///

     /// Constructor for EdgeReader. It creates the EdgeReader and

     /// attach it into the given LemonReader. It will use the given

     /// edge id reader to give back the edges. The reader will read the 

     /// section only if the \c _name and the \c edges_name are the same. 

     template <typename _LabelReader>

     EdgeReader(LemonReader& _reader, const _LabelReader& _labelReader, 

 	       const std::string& _name = std::string()) 

       : Parent(_reader), name(_name) {

       checkConcept<_reader_bits::ItemLabelReader<Edge>, _LabelReader>();

       edgeLabelReader.reset(new _reader_bits::

 			 LabelReader<Edge, _LabelReader>(_labelReader));

     }

     /// \brief Destructor.

     ///

     /// Destructor for EdgeReader.

     virtual ~EdgeReader() {}

   private:

     EdgeReader(const EdgeReader&);

     void operator=(const EdgeReader&);

   public:

     /// \brief Add an edge reader command for the EdgeReader.

     ///

     /// Add an edge reader command for the EdgeReader.

     void readEdge(std::string label, Edge& item) {

       if (readers.find(label) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for edge: " << label;

 	throw IoParameterError(msg.message());

       }

       readers.insert(make_pair(label, _reader_bits::ItemStore<Edge>(item)));

     }

   protected:

     /// \brief Gives back true when the SectionReader can process 

     /// the section with the given header line.

     ///

     /// It gives back true when the header line start with \c \@edges,

     /// and the header line's name and the reader's name are the same.

     virtual bool header(const std::string& line) {

       std::istringstream ls(line);

       std::string command;

       std::string id;

       ls >> command >> id;

       return command == "@edges" && name == id;

     }

     /// \brief Reader function of the section.

     ///

     /// It reads the content of the section.

     virtual void read(std::istream& is) {

       if (!edgeLabelReader->isLabelReader()) {

 	throw DataFormatError("Cannot find edgeset or label map");

       }

       std::string line;

       while (getline(is, line)) {

 	std::istringstream ls(line);

 	std::string id;

 	ls >> id;

 	typename EdgeReaders::iterator it = readers.find(id);

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

 	  it->second.read(edgeLabelReader->read(ls));

 	  it->second.touch();

 	}	

       }

       for (typename EdgeReaders::iterator it = readers.begin();

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

 	if (!it->second.touched()) {

 	  ErrorMessage msg;

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

 	  throw IoParameterError(msg.message());

 	}

       }

     }

     virtual void missing() {

       if (readers.empty()) return;

       ErrorMessage msg;

       msg << "Edges section not found in file: @edges " << name;

       throw IoParameterError(msg.message());

     }

   private:

     std::string name;

     typedef std::map<std::string, _reader_bits::ItemStore<Edge> > EdgeReaders;

     EdgeReaders readers;

     std::auto_ptr<_reader_bits::LabelReaderBase<Edge> > edgeLabelReader;

   };

   /// \ingroup section_io

   /// \brief SectionReader for reading labeled undirected edges.

   ///

   /// The undirected edges section's header line is \c \@uedges 

   /// \c uedges_name, but the \c uedges_name may be empty.

   ///

   /// Each line in the section contains the name of the undirected edge 

   /// and then the undirected edge id. 

   ///

   /// \relates LemonReader

   template <typename _Graph>

   class UEdgeReader : public LemonReader::SectionReader {

     typedef LemonReader::SectionReader Parent;

     typedef _Graph Graph;

     typedef typename Graph::Edge Edge;

     typedef typename Graph::UEdge UEdge;

   public:

     /// \brief Constructor.

     ///

     /// Constructor for UEdgeReader. It creates the UEdgeReader and

     /// attach it into the given LemonReader. It will use the given

     /// undirected edge id reader to give back the edges. The reader will 

     /// read the section only if the \c _name and the \c uedges_name are 

     /// the same. 

     template <typename _LabelReader>

     UEdgeReader(LemonReader& _reader, const _LabelReader& _labelReader, 

 	       const std::string& _name = std::string()) 

       : Parent(_reader), name(_name) {

       checkConcept<_reader_bits::ItemLabelReader<UEdge>, _LabelReader>();

       checkConcept<_reader_bits::ItemLabelReader<Edge>, _LabelReader>();

       uedgeLabelReader.reset(new _reader_bits::

 			     LabelReader<UEdge, _LabelReader>(_labelReader));

       edgeLabelReader.reset(new _reader_bits::

 			    LabelReader<Edge, _LabelReader>(_labelReader));

     }

     /// \brief Destructor.

     ///

     /// Destructor for UEdgeReader.

     virtual ~UEdgeReader() {}

   private:

     UEdgeReader(const UEdgeReader&);

     void operator=(const UEdgeReader&);

   public:

     /// \brief Add an undirected edge reader command for the UEdgeReader.

     ///

     /// Add an undirected edge reader command for the UEdgeReader.

     void readUEdge(std::string label, UEdge& item) {

       if (uedgeReaders.find(label) != uedgeReaders.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for undirected edge: " << label;

 	throw IoParameterError(msg.message());

       }

       uedgeReaders.insert(make_pair(label, _reader_bits::

 					ItemStore<UEdge>(item)));

     }

     /// \brief Add an edge reader command for the UEdgeReader.

     ///

     /// Add an edge reader command for the UEdgeReader.

     void readEdge(std::string label, Edge& item) {

       if (edgeReaders.find(label) != edgeReaders.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for edge: " << label;

 	throw IoParameterError(msg.message());

       }

       edgeReaders.insert(make_pair(label, _reader_bits::ItemStore<Edge>(item)));

     }

   protected:

     /// \brief Gives back true when the SectionReader can process 

     /// the section with the given header line.

     ///

     /// It gives back true when the header line start with \c \@edges,

     /// and the header line's name and the reader's name are the same.

     virtual bool header(const std::string& line) {

       std::istringstream ls(line);

       std::string command;

       std::string id;

       ls >> command >> id;

       return command == "@uedges" && name == id;

     }

     /// \brief Reader function of the section.

     ///

     /// It reads the content of the section.

     virtual void read(std::istream& is) {

       if (!edgeLabelReader->isLabelReader()) {

 	throw DataFormatError("Cannot find undirected edgeset or label map");

       }

       if (!uedgeLabelReader->isLabelReader()) {

 	throw DataFormatError("Cannot find undirected edgeset or label map");

       }

       std::string line;

       while (getline(is, line)) {

 	std::istringstream ls(line);

 	std::string id;

 	ls >> id;

 	{

 	  typename UEdgeReaders::iterator it = uedgeReaders.find(id);

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

 	    it->second.read(uedgeLabelReader->read(ls));

 	    it->second.touch();

 	    continue;

 	  }	

 	} {

 	  typename EdgeReaders::iterator it = edgeReaders.find(id);

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

 	    it->second.read(edgeLabelReader->read(ls));

 	    it->second.touch();

 	    continue;

 	  }	

 	}

       }

       for (typename EdgeReaders::iterator it = edgeReaders.begin();

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

 	if (!it->second.touched()) {

 	  ErrorMessage msg;

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

 	  throw IoParameterError(msg.message());

 	}

       }

       for (typename UEdgeReaders::iterator it = uedgeReaders.begin();

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

 	if (!it->second.touched()) {

 	  ErrorMessage msg;

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

 	  throw IoParameterError(msg.message());

 	}

       }

     }

     virtual void missing() {

       if (edgeReaders.empty() && uedgeReaders.empty()) return;

       ErrorMessage msg;

       msg << "UEdges section not found in file: @uedges " << name;

       throw IoParameterError(msg.message());

     }

   private:

     std::string name;

     typedef std::map<std::string, 

 		     _reader_bits::ItemStore<UEdge> > UEdgeReaders;

     UEdgeReaders uedgeReaders;

     std::auto_ptr<_reader_bits::LabelReaderBase<UEdge> > uedgeLabelReader;

     typedef std::map<std::string, _reader_bits::ItemStore<Edge> > EdgeReaders;

     EdgeReaders edgeReaders;

     std::auto_ptr<_reader_bits::LabelReaderBase<Edge> > edgeLabelReader;

   };

   /// \ingroup section_io

   /// \brief SectionReader for attributes.

   ///

   /// The lemon format can store multiple attribute set. Each set has

   /// the header line \c \@attributes \c attributeset_name, but the 

   /// attributeset_name may be empty.

   ///

   /// The attributeset section contains several lines. Each of them starts

   /// with an attribute and then a the value for the id.

   ///

   /// \relates LemonReader

   template <typename _Traits = DefaultReaderTraits>

   class AttributeReader : public LemonReader::SectionReader {

     typedef LemonReader::SectionReader Parent;

     typedef _Traits Traits; 

   public:

     /// \brief Constructor.

     ///

     /// Constructor for AttributeReader. It creates the AttributeReader and

     /// attach it into the given LemonReader. The reader process a section

     /// only if the \c section_name and the \c _name are the same.

     AttributeReader(LemonReader& _reader, 

 		    const std::string& _name = std::string()) 

       : Parent(_reader), name(_name) {}

     /// \brief Destructor.

     ///

     /// Destructor for AttributeReader.

     virtual ~AttributeReader() {

       for (typename Readers::iterator it = readers.begin(); 

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

 	delete it->second;

       }

     }

   private:

     AttributeReader(const AttributeReader&);

     void operator=(AttributeReader&);

   public:

     /// \brief Add an attribute reader command for the reader.

     ///

     /// Add an attribute reader command for the reader.

     template <typename Value>

     AttributeReader& readAttribute(const std::string& label, Value& value) {

       return readAttribute<typename Traits::template Reader<Value> >

 	(label, value);

     }

     /// \brief Add an attribute reader command for the reader.

     ///

     /// Add an attribute reader command for the reader.

     template <typename ItemReader, typename Value>

     AttributeReader& readAttribute(const std::string& label, Value& value,

 				   const ItemReader& ir = ItemReader()) {

       checkConcept<_reader_bits::ItemReader<Value>, ItemReader>();

       if (readers.find(label) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for attribute: " << label;

 	throw IoParameterError(msg.message());

       }

       readers.insert(make_pair(label, new _reader_bits::

 			       ValueReader<Value, ItemReader>(value, ir)));

       return *this;

     }

   protected:

     /// \brief Gives back true when the SectionReader can process 

     /// the section with the given header line.

     ///

     /// It gives back true when the header line start with \c \@attributes,

     /// and the header line's id and the attributeset's id are the same.

     bool header(const std::string& line) {

       std::istringstream ls(line);

       std::string command;

       std::string id;

       ls >> command >> id;

       return command == "@attributes" && name == id;

     }

     /// \brief Reader function of the section.

     ///

     /// It reads the content of the section.

     void read(std::istream& is) {

       std::string line;

       while (getline(is, line)) {

 	std::istringstream ls(line);

 	std::string id;

 	ls >> id;

 	typename Readers::iterator it = readers.find(id);

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

 	  it->second->read(ls);

  	  it->second->touch();

 	}

       }

       for (typename Readers::iterator it = readers.begin();

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

 	if (!it->second->touched()) {

 	  ErrorMessage msg;

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

 	  throw IoParameterError(msg.message());

 	}	

       }

     }    

     virtual void missing() {

       if (readers.empty()) return;

       ErrorMessage msg;

       msg << "Attribute section not found in file: @attributes " << name;

       throw IoParameterError(msg.message());

     }

   private:

     std::string name;

     typedef std::map<std::string, _reader_bits::ValueReaderBase*> Readers;

     Readers readers;  

   };

   /// \ingroup section_io

   /// \brief SectionReader for reading extra node maps.

   ///

   /// The lemon format can store maps in the nodeset sections. This

   /// class let you make distinict section to store maps.  The main

   /// purpose of this class is a logical separation of some maps. The

   /// other useful application could be to store paths in node maps.

   ///

   /// The first line of the section contains the names of the maps

   /// separated with white spaces. Each next line describes an item

   /// in the itemset, and contains in the first column the label of

   /// the item and then the mapped values for each map.

   ///

   /// \relates LemonReader

   template <typename _Graph, typename _Traits = DefaultReaderTraits>

   class NodeMapReader : public LemonReader::SectionReader {

     typedef LemonReader::SectionReader Parent;

   public:

     typedef _Graph Graph;

     typedef typename Graph::Node Node;

     typedef _Traits Traits;

     typedef typename Traits::Skipper DefaultSkipper;

     /// \brief Constructor.

     ///

     /// Constructor for NodeMapReader. It creates the NodeMapReader and

     /// attach it into the given LemonReader. The reader will read

     /// the section when the \c section_name and the \c _name are the same.

     template <typename _LabelReader>

     NodeMapReader(LemonReader& _reader, 

 		  const Graph& _graph, 

 		  const _LabelReader& _labelReader,

 		  const std::string& _name = std::string(),

 		  const DefaultSkipper& _skipper = DefaultSkipper()) 

       : Parent(_reader), graph(_graph), name(_name), skipper(_skipper) {

       labelReader.reset(new _reader_bits::

 			LabelReader<Node, _LabelReader>(_labelReader));

     } 

     /// \brief Destructor.

     ///

     /// Destructor for NodeMapReader.

     virtual ~NodeMapReader() {

       for (typename MapReaders::iterator it = readers.begin(); 

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

 	delete it->second;

       }

     }

   private:

     NodeMapReader(const NodeMapReader&);

     void operator=(const NodeMapReader&);

   public:

     /// \brief Add a new node map reader command for the reader.

     ///

     /// Add a new node map reader command for the reader.

     template <typename Map>

     NodeMapReader& readNodeMap(std::string label, Map& map) {

       return _readMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename _reader_bits::Arg<Map>::Type>(label, map);

     }

     template <typename Map>

     NodeMapReader& readNodeMap(std::string label, const Map& map) {

       return _readMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename _reader_bits::Arg<Map>::Type>(label, map);

     }

     /// \brief Add a new node map reader command for the reader.

     ///

     /// Add a new node map reader command for the reader.

     template <typename ItemReader, typename Map>

     NodeMapReader& readNodeMap(std::string label, Map& map, 

 			       const ItemReader& ir = ItemReader()) {

       return _readMap<ItemReader, Map, typename _reader_bits::Arg<Map>::Type>

 	(label, map, ir);

     }

     template <typename ItemReader, typename Map>

     NodeMapReader& readNodeMap(std::string label, const Map& map, 

 			       const ItemReader& ir = ItemReader()) {

       return _readMap<ItemReader, Map, typename _reader_bits::Arg<Map>::Type>

 	(label, map, ir);

     }

   private:

     template <typename ItemReader, typename Map, typename MapParameter>

     NodeMapReader& _readMap(std::string label, MapParameter map, 

 			   const ItemReader& ir = ItemReader()) {

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

       checkConcept<_reader_bits::ItemReader<typename Map::Value>, ItemReader>();

       if (readers.find(label) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for map: " << label;