diff -r d8475431bbbb -r 8e85e6bbefdf src/lemon/lemon_writer.h
--- a/src/lemon/lemon_writer.h	Sat May 21 21:04:57 2005 +0000
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,1129 +0,0 @@
-/* -*- C++ -*-
- * src/lemon/lemon_writer.h - Part of LEMON, a generic C++ optimization library
- *
- * Copyright (C) 2005 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 io_group
-///\file
-///\brief Lemon Format writer.
-
-#ifndef LEMON_LEMON_WRITER_H
-#define LEMON_LEMON_WRITER_H
-
-#include <iostream>
-#include <fstream>
-#include <string>
-#include <vector>
-#include <algorithm>
-#include <map>
-#include <memory>
-
-#include <lemon/error.h>
-#include <lemon/invalid.h>
-#include <lemon/graph_utils.h>
-#include <lemon/bits/item_writer.h>
-#include <lemon/utility.h>
-#include <lemon/maps.h>
-
-
-namespace lemon {
-
-  /// \ingroup io_group
-  /// \brief Lemon Format writer 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 write a section oriented format.
-  ///
-  /// In the Lemon Format each section starts with a line contains a \c \@
-  /// character on the first not white space position. This line is the
-  /// header line of the section. Each next lines belong to this section
-  /// while it does not starts with \c \@ character. This line can start a 
-  /// new section or if it can close the file with the \c \@end line.
-  /// The file format ignore the empty lines and it may contain comments
-  /// started with a \c # character to the end of the line. 
-  ///
-  /// The framework provides an abstract LemonWriter::SectionWriter class
-  /// what defines the interface of a SectionWriter. The SectionWriter
-  /// has the \c header() member function what gives back the header of the
-  /// section. After that it will be called the \c write() member which
-  /// should write the content of the section.
-  ///
-  /// \relates GraphWriter
-  /// \relates NodeSetWriter
-  /// \relates EdgeSetWriter
-  /// \relates NodesWriter
-  /// \relates EdgesWriter
-  /// \relates AttributeWriter
-  class LemonWriter {
-  public:
-
-    /// \brief Abstract base class for writing a section.
-    ///
-    /// This class has an \c header() member function what gives back
-    /// the header line of the section. The \c write() member should
-    /// write the content of the section to the stream.
-    class SectionWriter {
-      friend class LemonWriter;
-    protected:
-      /// \brief Constructor for SectionWriter.
-      ///
-      /// Constructor for SectionWriter. It attach this writer to
-      /// the given LemonWriter.
-      SectionWriter(LemonWriter& writer) {
-	writer.attach(*this);
-      }
-
-      /// \brief The header of section.
-      ///
-      /// It gives back the header of the section.
-      virtual std::string header() = 0;
-
-      /// \brief  Writer function of the section.
-      ///
-      /// Write the content of the section.
-      virtual void write(std::ostream& os) = 0;
-    };
-
-    /// \brief Constructor for LemonWriter.
-    ///
-    /// Constructor for LemonWriter which writes to the given stream.
-    LemonWriter(std::ostream& _os) 
-      : os(&_os), own_os(false) {}
-
-    /// \brief Constructor for LemonWriter.
-    ///
-    /// Constructor for LemonWriter which writes to the given file.
-    LemonWriter(const std::string& filename) 
-      : os(0), own_os(true) {
-      os = new std::ofstream(filename.c_str());
-    }
-
-    /// \brief Desctructor for LemonWriter.
-    ///
-    /// Desctructor for LemonWriter.
-    ~LemonWriter() {
-      if (own_os) {
-	delete os;
-      }
-    }
-
-  private:
-    LemonWriter(const LemonWriter&);
-    void operator=(const LemonWriter&);
-
-    void attach(SectionWriter& writer) {
-      writers.push_back(&writer);
-    }
-
-  public:
-
-    /// \brief Executes the LemonWriter.
-    /// 
-    /// It executes the LemonWriter.
-    void run() {
-      SectionWriters::iterator it;
-      for (it = writers.begin(); it != writers.end(); ++it) {
-	*os << (*it)->header() << std::endl;
-	(*it)->write(*os);
-      }
-      *os << "@end" << std::endl;
-    }
-
-
-  private:
-
-    std::ostream* os;
-    bool own_os;
-
-    typedef std::vector<SectionWriter*> SectionWriters;
-    SectionWriters writers;
-
-  };
-
-  /// \brief Helper class for implementing the common SectionWriters.
-  ///
-  /// Helper class for implementing the common SectionWriters.
-  class CommonSectionWriterBase : public LemonWriter::SectionWriter {
-    typedef LemonWriter::SectionWriter Parent;
-  protected:
-    
-    /// \brief Constructor for CommonSectionWriterBase.
-    ///
-    /// Constructor for CommonSectionWriterBase. It attach this writer to
-    /// the given LemonWriter.
-    CommonSectionWriterBase(LemonWriter& _writer) 
-      : Parent(_writer) {}
-
-    template <typename _Item>    
-    class WriterBase {
-    public:
-      typedef _Item Item;
-
-      virtual ~WriterBase() {}
-
-      virtual void write(std::ostream& os, const Item& item) = 0;
-    };
-
-
-    template <typename _Item, typename _Map, typename _Writer>
-    class MapWriter : public WriterBase<_Item> {
-    public:
-      typedef _Map Map;
-      typedef _Writer Writer;
-      typedef typename Writer::Value Value;
-      typedef _Item Item;
-      
-      typename SmartConstReference<Map>::Type map;
-      Writer writer;
-
-      MapWriter(const Map& _map, const Writer& _writer) 
-	: map(_map), writer(_writer) {}
-
-      virtual ~MapWriter() {}
-
-      virtual void write(std::ostream& os, const Item& item) {
-	Value value = map[item];
-	writer.write(os, value);
-      }
-
-    };
-
-
-    class ValueWriterBase {
-    public:
-      virtual void write(std::ostream&) = 0;
-    };
-
-    template <typename _Value, typename _Writer>
-    class ValueWriter : public ValueWriterBase {
-    public:
-      typedef _Value Value;
-      typedef _Writer Writer;
-
-      ValueWriter(const Value& _value, const Writer& _writer)
- 	: value(_value), writer(_writer) {}
-
-      virtual void write(std::ostream& os) {
-	writer.write(os, value);
-      }
-    private:
-      const Value& value;
-      Writer writer;
-    };
-    
-
-    template <typename _Item>
-    class IdWriterBase {
-    public:
-      typedef _Item Item;
-      virtual void write(std::ostream&, const Item&) const = 0;
-    };
-
-    template <typename _Item, typename _BoxedIdWriter>
-    class IdWriter : public IdWriterBase<_Item> {
-    public:
-      typedef _Item Item;
-      typedef _BoxedIdWriter BoxedIdWriter;
-
-      const BoxedIdWriter& idWriter;
-
-      IdWriter(const BoxedIdWriter& _idWriter) 
-	: idWriter(_idWriter) {}
-
-      virtual void write(std::ostream& os, const Item& item) const {
-	idWriter.writeId(os, item);
-      }
-    };
-  };
-
-  /// \ingroup io_group
-  /// \brief SectionWriter for writing 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_id, but the
-  /// \c nodeset_id 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 "id" named map then it will be regarded
-  /// as id map. This map should contain only unique values and when the 
-  /// \c writeId() member will be called with a node it will write it's id.
-  /// Otherwise if the \c _forceIdMap constructor parameter is true then
-  /// the id map will be the id in the graph.
-  ///
-  /// \relates LemonWriter
-  template <typename _Graph, typename _Traits = DefaultWriterTraits>
-  class NodeSetWriter : public CommonSectionWriterBase {
-    typedef CommonSectionWriterBase Parent;
-  public:
-
-    typedef _Graph Graph;
-    typedef _Traits Traits;
-    typedef typename Graph::Node Node;
-
-    /// \brief Constructor.
-    ///
-    /// Constructor for NodeSetWriter. It creates the NodeSetWriter and
-    /// attach it into the given LemonWriter. If the \c _forceIdMap
-    /// parameter is true then the writer will write own id map when
-    /// the user does not give "id" named map.
-    NodeSetWriter(LemonWriter& _writer, const Graph& _graph, 
-		  const std::string& _id = std::string(), 
-		  bool _forceIdMap = true) 
-      : Parent(_writer), idMap(0), forceIdMap(_forceIdMap), 
-	graph(_graph), id(_id) {}
-
-    /// \brief Destructor.
-    ///
-    /// Destructor for NodeSetWriter.
-    virtual ~NodeSetWriter() {
-      typename MapWriters::iterator it;
-      for (it = writers.begin(); it != writers.end(); ++it) {
-	delete it->second;
-      }
-    }
-
-  private:
-    NodeSetWriter(const NodeSetWriter&);
-    void operator=(const NodeSetWriter&);
-  
-  public:
-
-    /// \brief Add a new node map writer command for the writer.
-    ///
-    /// Add a new node map writer command for the writer.
-    template <typename Map>
-    NodeSetWriter& writeNodeMap(std::string name, const Map& map) {
-      return writeNodeMap<typename Traits::
-	template Writer<typename Map::Value>, Map>(name, map);
-    }
-
-    /// \brief Add a new node map writer command for the writer.
-    ///
-    /// Add a new node map writer command for the writer.
-    template <typename Writer, typename Map>
-    NodeSetWriter& writeNodeMap(std::string name, const Map& map, 
-			    const Writer& writer = Writer()) {
-      writers.push_back(
-	make_pair(name, new MapWriter<Node, Map, Writer>(map, writer)));
-      return *this;
-    }
-
-  protected:
-
-    /// \brief The header of the section.
-    ///
-    /// It gives back the header of the section.
-    virtual std::string header() {
-      return "@nodeset " + id;
-    }
-
-    /// \brief  Writer function of the section.
-    ///
-    /// Write the content of the section.
-    virtual void write(std::ostream& os) {
-      for (int i = 0; i < (int)writers.size(); ++i) {
-	if (writers[i].first == "id") {
-	  idMap = writers[i].second;
-	  forceIdMap = false;
-	  break;
-	}
-      }
-      if (forceIdMap) {
-	os << "id\t";
-      }
-      for (int i = 0; i < (int)writers.size(); ++i) {
-	os << writers[i].first << '\t';
-      }
-      os << std::endl;
-      for (typename Graph::NodeIt it(graph); it != INVALID; ++it) {
-	if (forceIdMap) {
-	  os << graph.id(it) << '\t';
-	}
-	for (int i = 0; i < (int)writers.size(); ++i) {
-	  writers[i].second->write(os, it);
-	  os << '\t';
-	}
-	os << std::endl;
-      }
-    }
-
-  public:
-
-    /// \brief Returns true if the nodeset can write the ids of the nodes.
-    ///
-    /// Returns true if the nodeset can write the ids of the nodes.
-    /// It is possible only if an "id" named map was written or the 
-    /// \c _forceIdMap constructor parameter was true.
-    bool isIdWriter() const {
-      return idMap != 0 || forceIdMap;
-    }
-
-    /// \brief Write the id of the given node.
-    ///
-    /// It writes the id of the given node. If there was written an "id"
-    /// named map then it will write the map value belongs to the node.
-    /// Otherwise if the \c forceId parameter was true it will write
-    /// its id in the graph. 
-    void writeId(std::ostream& os, const Node& item) const {
-      if (forceIdMap) {
-	os << graph.id(item);
-      } else {
-	idMap->write(os, item);
-      }
-    }
-
-  private:
-
-    typedef std::vector<std::pair<std::string, WriterBase<Node>*> > MapWriters;
-    MapWriters writers;
-
-    WriterBase<Node>* idMap;
-    bool forceIdMap;
-   
-    typename SmartConstReference<Graph>::Type graph;   
-    std::string id;
-
-  };
-
-  /// \ingroup io_group
-  /// \brief SectionWriter for writing a graph's edgesets.
-  ///
-  /// The lemon format can store multiple graph edgesets with several maps. 
-  /// The edgeset section's header line is \c \@edgeset \c edgeset_id, but the
-  /// \c edgeset_id may be empty.
-  ///
-  /// The first line of the section contains the names of the maps separated
-  /// with white spaces. Each next lines describes a 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 "id" named map then it will be regarded
-  /// as id map. This map should contain only unique values and when the 
-  /// \c writeId() member will be called with an edge it will write it's id.
-  /// Otherwise if the \c _forceIdMap constructor parameter is true then
-  /// the id map will be the id in the graph.
-  ///
-  /// The edgeset writer needs a node id writer to identify which nodes
-  /// have to be connected. If a NodeSetWriter can write the nodes' id,
-  /// it will be able to use with this class.
-  ///
-  /// \relates LemonWriter
-  template <typename _Graph, typename _Traits = DefaultWriterTraits>
-  class EdgeSetWriter : public CommonSectionWriterBase {
-    typedef CommonSectionWriterBase Parent;
-  public:
-
-    typedef _Graph Graph;
-    typedef _Traits Traits;
-    typedef typename Graph::Node Node;
-    typedef typename Graph::Edge Edge;
-
-    /// \brief Constructor.
-    ///
-    /// Constructor for EdgeSetWriter. It creates the EdgeSetWriter and
-    /// attach it into the given LemonWriter. It will write node ids by
-    /// the \c _nodeIdWriter. If the \c _forceIdMap parameter is true 
-    /// then the writer will write own id map if the user does not give 
-    /// "id" named map.
-    template <typename NodeIdWriter>
-    EdgeSetWriter(LemonWriter& _writer, const Graph& _graph, 
-		  const NodeIdWriter& _nodeIdWriter, 
-		  const std::string& _id = std::string(),
-		  bool _forceIdMap = true)
-      : Parent(_writer), idMap(0), forceIdMap(_forceIdMap),
-	graph(_graph), id(_id),
-	nodeIdWriter(new IdWriter<Node, NodeIdWriter>(_nodeIdWriter)) {} 
-
-    /// \brief Destructor.
-    ///
-    /// Destructor for EdgeSetWriter.
-    virtual ~EdgeSetWriter() {
-      typename MapWriters::iterator it;
-      for (it = writers.begin(); it != writers.end(); ++it) {
-	delete it->second;
-      }
-    }
-
-  private:
-    EdgeSetWriter(const EdgeSetWriter&);
-    void operator=(const EdgeSetWriter&);
-
-  public:
-
-    /// \brief Add a new edge map writer command for the writer.
-    ///
-    /// Add a new edge map writer command for the writer.
-    template <typename Map>
-    EdgeSetWriter& writeEdgeMap(std::string name, const Map& map) {
-      return writeEdgeMap<typename Traits::
-	template Writer<typename Map::Value>, Map>(name, map);
-    }
-
-    /// \brief Add a new edge map writer command for the writer.
-    ///
-    /// Add a new edge map writer command for the writer.
-    template <typename Writer, typename Map>
-    EdgeSetWriter& writeEdgeMap(std::string name, const Map& map, 
-			    const Writer& writer = Writer()) {
-      writers.push_back(
-	make_pair(name, new MapWriter<Edge, Map, Writer>(map, writer)));
-      return *this;
-    }
-
-  protected:
-
-    /// \brief The header of the section.
-    ///
-    /// It gives back the header of the section.
-    virtual std::string header() {
-      return "@edgeset " + id;
-    }
-
-    /// \brief  Writer function of the section.
-    ///
-    /// Write the content of the section.
-    virtual void write(std::ostream& os) {
-      for (int i = 0; i < (int)writers.size(); ++i) {
-	if (writers[i].first == "id") {
-	  idMap = writers[i].second;
-	  forceIdMap = false;
-	  break;
-	}
-      }
-      os << "\t\t";
-      if (forceIdMap) {
-	os << "id\t";
-      }
-      for (int i = 0; i < (int)writers.size(); ++i) {
-	os << writers[i].first << '\t';
-      }
-      os << std::endl;
-      for (typename Graph::EdgeIt it(graph); it != INVALID; ++it) {
-	nodeIdWriter->write(os, graph.source(it));
-	os << '\t';
-	nodeIdWriter->write(os, graph.target(it));
-	os << '\t';
-	if (forceIdMap) {
-	  os << graph.id(it) << '\t';
-	}
-	for (int i = 0; i < (int)writers.size(); ++i) {
-	  writers[i].second->write(os, it);
-	  os << '\t';
-	}
-	os << std::endl;
-      }
-    }
-
-  public:
-
-    /// \brief Returns true if the edgeset can write the ids of the edges.
-    ///
-    /// Returns true if the edgeset can write the ids of the edges.
-    /// It is possible only if an "id" named map was written or the 
-    /// \c _forceIdMap constructor parameter was true.
-    bool isIdWriter() const {
-      return forceIdMap || idMap != 0;
-    }
-
-    /// \brief Write the id of the given edge.
-    ///
-    /// It writes the id of the given edge. If there was written an "id"
-    /// named map then it will write the map value belongs to the edge.
-    /// Otherwise if the \c forceId parameter was true it will write
-    /// its id in the graph. 
-    void writeId(std::ostream& os, const Edge& item) const {
-      if (forceIdMap) {
-	os << graph.id(item);
-      } else {
-	idMap->write(os, item);
-      }
-    } 
-
-  private:
-
-    typedef std::vector<std::pair<std::string, WriterBase<Edge>*> > MapWriters;
-    MapWriters writers;
-
-    WriterBase<Edge>* idMap;
-    bool forceIdMap;
-   
-    typename SmartConstReference<Graph>::Type graph;   
-    std::string id;
-
-    std::auto_ptr<IdWriterBase<Node> > nodeIdWriter;
-  };
-
-  /// \ingroup io_group
-  /// \brief SectionWriter for writing a undirected edgeset.
-  ///
-  /// The lemon format can store multiple undirected edgesets with several 
-  /// maps. The undirected edgeset section's header line is \c \@undiredgeset 
-  /// \c undiredgeset_id, but the \c undiredgeset_id may be empty.
-  ///
-  /// The first line of the section contains the names of the maps separated
-  /// with white spaces. Each next lines describes an undirected edge in the 
-  /// edgeset. The line contains the two connected nodes' id and the mapped 
-  /// values for each undirected 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 "id" named map then it will be regarded
-  /// as id map. This map should contain only unique values and when the 
-  /// \c writeId() member will be called with an undirected edge it will 
-  /// write it's id. Otherwise if the \c _forceIdMap constructor parameter
-  /// is true then the id map will be the id in the graph.
-  ///
-  /// The undirected edgeset writer needs a node id writer to identify 
-  /// which nodes have to be connected. If a NodeSetWriter can write the 
-  /// nodes' id, it will be able to use with this class.
-  ///
-  /// \relates LemonWriter
-  template <typename _Graph, typename _Traits = DefaultWriterTraits>
-  class UndirEdgeSetWriter : public CommonSectionWriterBase {
-    typedef CommonSectionWriterBase Parent;
-  public:
-
-    typedef _Graph Graph;
-    typedef _Traits Traits;
-    typedef typename Graph::Node Node;
-    typedef typename Graph::Edge Edge;
-    typedef typename Graph::UndirEdge UndirEdge;
-
-    /// \brief Constructor.
-    ///
-    /// Constructor for UndirEdgeSetWriter. It creates the UndirEdgeSetWriter
-    /// and attach it into the given LemonWriter. It will write node ids by
-    /// the \c _nodeIdWriter. If the \c _forceIdMap parameter is true 
-    /// then the writer will write own id map if the user does not give 
-    /// "id" named map.
-    template <typename NodeIdWriter>
-    UndirEdgeSetWriter(LemonWriter& _writer, const Graph& _graph, 
-		       const NodeIdWriter& _nodeIdWriter, 
-		       const std::string& _id = std::string(),
-		       bool _forceIdMap = true)
-      : Parent(_writer), idMap(0), forceIdMap(_forceIdMap),
-	graph(_graph), id(_id),
-	nodeIdWriter(new IdWriter<Node, NodeIdWriter>(_nodeIdWriter)) {} 
-
-    /// \brief Destructor.
-    ///
-    /// Destructor for UndirEdgeSetWriter.
-    virtual ~UndirEdgeSetWriter() {
-      typename MapWriters::iterator it;
-      for (it = writers.begin(); it != writers.end(); ++it) {
-	delete it->second;
-      }
-    }
-
-  private:
-    UndirEdgeSetWriter(const UndirEdgeSetWriter&);
-    void operator=(const UndirEdgeSetWriter&);
-
-  public:
-
-    /// \brief Add a new undirected edge map writer command for the writer.
-    ///
-    /// Add a new undirected map writer command for the writer.
-    template <typename Map>
-    UndirEdgeSetWriter& writeUndirEdgeMap(std::string name, const Map& map) {
-      return writeUndirEdgeMap<typename Traits::
-	template Writer<typename Map::Value>, Map>(name, map);
-    }
-
-    /// \brief Add a new undirected map writer command for the writer.
-    ///
-    /// Add a new undirected map writer command for the writer.
-    template <typename Writer, typename Map>
-    UndirEdgeSetWriter& writeUndirEdgeMap(std::string name, const Map& map, 
-					  const Writer& writer = Writer()) {
-      writers.push_back(
-	make_pair(name, new MapWriter<UndirEdge, Map, Writer>(map, writer)));
-      return *this;
-    }
-
-    /// \brief Add a new directed edge map writer command for the writer.
-    ///
-    /// Add a new directed map writer command for the writer.
-    template <typename Map>
-    UndirEdgeSetWriter& writeEdgeMap(std::string name, const Map& map) {
-      writeUndirEdgeMap("+" + name, composeMap(forwardMap(graph), map));
-      writeUndirEdgeMap("-" + name, composeMap(backwardMap(graph), map));
-      return *this;
-    }
-
-    /// \brief Add a new directed map writer command for the writer.
-    ///
-    /// Add a new directed map writer command for the writer.
-    template <typename Writer, typename Map>
-    UndirEdgeSetWriter& writeEdgeMap(std::string name, const Map& map, 
-				     const Writer& writer = Writer()) {
-      writeUndirEdge("+" + name, composeMap(forwardMap(graph), map), writer);
-      writeUndirEdge("-" + name, composeMap(forwardMap(graph), map), writer);
-      return *this;
-    }
-
-  protected:
-
-    /// \brief The header of the section.
-    ///
-    /// It gives back the header of the section.
-    virtual std::string header() {
-      return "@undiredgeset " + id;
-    }
-
-    /// \brief  Writer function of the section.
-    ///
-    /// Write the content of the section.
-    virtual void write(std::ostream& os) {
-      for (int i = 0; i < (int)writers.size(); ++i) {
-	if (writers[i].first == "id") {
-	  idMap = writers[i].second;
-	  forceIdMap = false;
-	  break;
-	}
-      }
-      os << "\t\t";
-      if (forceIdMap) {
-	os << "id\t";
-      }
-      for (int i = 0; i < (int)writers.size(); ++i) {
-	os << writers[i].first << '\t';
-      }
-      os << std::endl;
-      for (typename Graph::UndirEdgeIt it(graph); it != INVALID; ++it) {
-	nodeIdWriter->write(os, graph.source(it));
-	os << '\t';
-	nodeIdWriter->write(os, graph.target(it));
-	os << '\t';
-	if (forceIdMap) {
-	  os << graph.id(it) << '\t';
-	}
-	for (int i = 0; i < (int)writers.size(); ++i) {
-	  writers[i].second->write(os, it);
-	  os << '\t';
-	}
-	os << std::endl;
-      }
-    }
-
-  public:
-
-    /// \brief Returns true if the undirected edgeset can write the ids of 
-    /// the edges.
-    ///
-    /// Returns true if the undirected edgeset can write the ids of the 
-    /// undirected edges. It is possible only if an "id" named map was 
-    /// written or the \c _forceIdMap constructor parameter was true.
-    bool isIdWriter() const {
-      return forceIdMap || idMap != 0;
-    }
-
-    /// \brief Write the id of the given undirected edge.
-    ///
-    /// It writes the id of the given undirected edge. If there was written 
-    /// an "id" named map then it will write the map value belongs to the 
-    /// undirected edge. Otherwise if the \c forceId parameter was true it 
-    /// will write its id in the graph. 
-    void writeId(std::ostream& os, const UndirEdge& item) const {
-      if (forceIdMap) {
-	os << graph.id(item);
-      } else {
-	idMap->write(os, item);
-      }
-    } 
-
-    /// \brief Write the id of the given edge.
-    ///
-    /// It writes the id of the given edge. If there was written 
-    /// an "id" named map then it will write the map value belongs to the 
-    /// edge. Otherwise if the \c forceId parameter was true it 
-    /// will write its id in the graph. If the edge is forward map
-    /// then its prefix character is \c '+' elsewhere \c '-'.
-    void writeId(std::ostream& os, const Edge& item) const {
-      if (graph.forward(item)) {
-	os << "+ ";
-      } else {
-	os << "- ";
-      }
-      if (forceIdMap) {
-	os << graph.id(item);
-      } else {
-	idMap->write(os, item);
-      }
-    } 
-
-  private:
-
-    typedef std::vector<std::pair<std::string, 
-				  WriterBase<UndirEdge>*> > MapWriters;
-    MapWriters writers;
-
-    WriterBase<UndirEdge>* idMap;
-    bool forceIdMap;
-   
-    typename SmartConstReference<Graph>::Type graph;   
-    std::string id;
-
-    std::auto_ptr<IdWriterBase<Node> > nodeIdWriter;
-  };
-
-  /// \ingroup io_group
-  /// \brief SectionWriter for writing labeled nodes.
-  ///
-  /// The nodes section's header line is \c \@nodes \c nodes_id, but the
-  /// \c nodes_id may be empty.
-  ///
-  /// Each line in the section contains the label of the node and 
-  /// then the node id. 
-  ///
-  /// \relates LemonWriter
-  template <typename _Graph>
-  class NodeWriter : public CommonSectionWriterBase {
-    typedef CommonSectionWriterBase Parent;
-    typedef _Graph Graph;
-    typedef typename Graph::Node Node;
-  public:
-    
-    /// \brief Constructor.
-    ///
-    /// Constructor for NodeWriter. It creates the NodeWriter and
-    /// attach it into the given LemonWriter. The given \c _IdWriter
-    /// will write the nodes' id what can be a nodeset writer.
-    template <typename _IdWriter>
-    NodeWriter(LemonWriter& _writer, const _IdWriter& _idWriter, 
-	       const std::string& _id = std::string()) 
-      : Parent(_writer), id(_id), 
-	idWriter(new IdWriter<typename Graph::Node, _IdWriter>(_idWriter)) {} 
-
-    /// \brief Destructor.
-    ///
-    /// Destructor for NodeWriter.
-    virtual ~NodeWriter() {}
-
-  private:
-    NodeWriter(const NodeWriter&);
-    void operator=(const NodeWriter&);
-
-  public:
-
-    /// \brief Add a node writer command for the NodeWriter.
-    ///
-    /// Add a node writer command for the NodeWriter.
-    void writeNode(const std::string& name, const Node& item) {
-      writers.push_back(make_pair(name, &item));
-    }
-
-  protected:
-
-    /// \brief Header checking function.
-    ///
-    /// It gives back true when the header line start with \c \@nodes,
-    /// and the header line's id and the writer's id are the same.
-    virtual std::string header() {
-      return "@nodes " + id;
-    }
-
-    /// \brief  Writer function of the section.
-    ///
-    /// Write the content of the section.
-    virtual void write(std::ostream& os) {
-      for (int i = 0; i < (int)writers.size(); ++i) {
-	os << writers[i].first << ' ';
-	idWriter->write(os, *(writers[i].second));
-	os << std::endl;
-      }
-    }
-    
-  private:
-
-    std::string id;
-
-    typedef std::vector<std::pair<std::string, const Node*> > NodeWriters;
-    NodeWriters writers;
-    std::auto_ptr<IdWriterBase<Node> > idWriter;
-  };
-
-  /// \ingroup io_group
-  /// \brief SectionWriter for writing labeled edges.
-  ///
-  /// The edges section's header line is \c \@edges \c edges_id, but the
-  /// \c edges_id may be empty.
-  ///
-  /// Each line in the section contains the label of the edge and 
-  /// then the edge id. 
-  ///
-  /// \relates LemonWriter
-  template <typename _Graph>
-  class EdgeWriter : public CommonSectionWriterBase {
-    typedef CommonSectionWriterBase Parent;
-    typedef _Graph Graph;
-    typedef typename Graph::Edge Edge;
-  public:
-    
-    /// \brief Constructor.
-    ///
-    /// Constructor for EdgeWriter. It creates the EdgeWriter and
-    /// attach it into the given LemonWriter. The given \c _IdWriter
-    /// will write the edges' id what can be a edgeset writer.
-    template <typename _IdWriter>
-    EdgeWriter(LemonWriter& _writer, const _IdWriter& _idWriter, 
-	       const std::string& _id = std::string()) 
-      : Parent(_writer), id(_id), 
-	idWriter(new IdWriter<typename Graph::Edge, _IdWriter>(_idWriter)) {} 
-
-    /// \brief Destructor.
-    ///
-    /// Destructor for EdgeWriter.
-    virtual ~EdgeWriter() {}
-  private:
-    EdgeWriter(const EdgeWriter&);
-    void operator=(const EdgeWriter&);
-
-  public:
-
-    /// \brief Add an edge writer command for the EdgeWriter.
-    ///
-    /// Add an edge writer command for the EdgeWriter.
-    void writeEdge(const std::string& name, const Edge& item) {
-      writers.push_back(make_pair(name, &item));
-    }
-
-  protected:
-
-    /// \brief Header checking function.
-    ///
-    /// It gives back true when the header line start with \c \@edges,
-    /// and the header line's id and the writer's id are the same.
-    virtual std::string header() {
-      return "@edges " + id;
-    }
-
-    /// \brief  Writer function of the section.
-    ///
-    /// Write the content of the section.
-    virtual void write(std::ostream& os) {
-      for (int i = 0; i < (int)writers.size(); ++i) {
-	os << writers[i].first << ' ';
-	idWriter->write(os, *(writers[i].second));
-	os << std::endl;
-      }
-    }
-    
-  private:
-
-    std::string id;
-
-    typedef std::vector<std::pair<std::string, const Edge*> > EdgeWriters;
-    EdgeWriters writers;
-
-    std::auto_ptr<IdWriterBase<Edge> > idWriter;
-  };
-
-  /// \ingroup io_group
-  /// \brief SectionWriter for writing labeled undirected edges.
-  ///
-  /// The undirected edges section's header line is \c \@undiredges 
-  /// \c undiredges_id, but the \c undiredges_id may be empty.
-  ///
-  /// Each line in the section contains the label of the undirected edge and 
-  /// then the undirected edge id. 
-  ///
-  /// \relates LemonWriter
-  template <typename _Graph>
-  class UndirEdgeWriter : public CommonSectionWriterBase {
-    typedef CommonSectionWriterBase Parent;
-    typedef _Graph Graph;
-    typedef typename Graph::Node Node;
-    typedef typename Graph::Edge Edge;
-    typedef typename Graph::UndirEdge UndirEdge;
-  public:
-    
-    /// \brief Constructor.
-    ///
-    /// Constructor for UndirEdgeWriter. It creates the UndirEdgeWriter and
-    /// attach it into the given LemonWriter. The given \c _IdWriter
-    /// will write the undirected edges' id what can be an undirected 
-    /// edgeset writer.
-    template <typename _IdWriter>
-    UndirEdgeWriter(LemonWriter& _writer, const _IdWriter& _idWriter, 
-	       const std::string& _id = std::string()) 
-      : Parent(_writer), id(_id), 
-	undirEdgeIdWriter(new IdWriter<UndirEdge, _IdWriter>(_idWriter)),
-	edgeIdWriter(new IdWriter<Edge, _IdWriter>(_idWriter)) {}
-
-    /// \brief Destructor.
-    ///
-    /// Destructor for UndirEdgeWriter.
-    virtual ~UndirEdgeWriter() {}
-  private:
-    UndirEdgeWriter(const UndirEdgeWriter&);
-    void operator=(const UndirEdgeWriter&);
-
-  public:
-
-    /// \brief Add an edge writer command for the UndirEdgeWriter.
-    ///
-    /// Add an edge writer command for the UndirEdgeWriter.
-    void writeEdge(const std::string& name, const Edge& item) {
-      edgeWriters.push_back(make_pair(name, &item));
-    }
-
-    /// \brief Add an undirected edge writer command for the UndirEdgeWriter.
-    ///
-    /// Add an undirected edge writer command for the UndirEdgeWriter.
-    void writeUndirEdge(const std::string& name, const UndirEdge& item) {
-      undirEdgeWriters.push_back(make_pair(name, &item));
-    }
-
-  protected:
-
-    /// \brief Header checking function.
-    ///
-    /// It gives back true when the header line start with \c \@undiredges,
-    /// and the header line's id and the writer's id are the same.
-    virtual std::string header() {
-      return "@undiredges " + id;
-    }
-
-    /// \brief  Writer function of the section.
-    ///
-    /// Write the content of the section.
-    virtual void write(std::ostream& os) {
-      for (int i = 0; i < (int)undirEdgeWriters.size(); ++i) {
-	os << undirEdgeWriters[i].first << ' ';
-	undirEdgeIdWriter->write(os, *(undirEdgeWriters[i].second));
-	os << std::endl;
-      }
-      for (int i = 0; i < (int)edgeWriters.size(); ++i) {
-	os << edgeWriters[i].first << ' ';
-	edgeIdWriter->write(os, *(edgeWriters[i].second));
-	os << std::endl;
-      }
-    }
-    
-  private:
-
-    std::string id;
-
-    typedef std::vector<std::pair<std::string, 
-				  const UndirEdge*> > UndirEdgeWriters;
-    UndirEdgeWriters undirEdgeWriters;
-    std::auto_ptr<IdWriterBase<UndirEdge> > undirEdgeIdWriter;
-
-    typedef std::vector<std::pair<std::string, const Edge*> > EdgeWriters;
-    EdgeWriters edgeWriters;
-    std::auto_ptr<IdWriterBase<Edge> > edgeIdWriter;
-
-  };
-
-  /// \ingroup io_group
-  /// \brief SectionWriter for attributes.
-  ///
-  /// The lemon format can store multiple attribute set. Each set has
-  /// the header line \c \@attributes \c attributeset_id, but the 
-  /// attributeset_id may be empty.
-  ///
-  /// The attributeset section contains several lines. Each of them starts
-  /// with the name of attribute and then the value.
-  ///
-  /// \relates LemonWriter
-  template <typename _Traits = DefaultWriterTraits>
-  class AttributeWriter : public CommonSectionWriterBase {
-    typedef CommonSectionWriterBase Parent;
-    typedef _Traits Traits; 
-  public:
-    /// \brief Constructor.
-    ///
-    /// Constructor for AttributeWriter. It creates the AttributeWriter and
-    /// attach it into the given LemonWriter.
-    AttributeWriter(LemonWriter& _writer, 
-		    const std::string& _id = std::string()) 
-      : Parent(_writer), id(_id) {}
-
-    /// \brief Destructor.
-    ///
-    /// Destructor for AttributeWriter.
-    virtual ~AttributeWriter() {
-      typename Writers::iterator it;
-      for (it = writers.begin(); it != writers.end(); ++it) {
-	delete it->second;
-      }
-    }
-
-  private:
-    AttributeWriter(const AttributeWriter&);
-    void operator=(AttributeWriter&);
-
-  public:
-    /// \brief Add an attribute writer command for the writer.
-    ///
-    /// Add an attribute writer command for the writer.
-    template <typename Value>
-    AttributeWriter& writeAttribute(const std::string& id, 
-				    const Value& value) {
-      return 
-	writeAttribute<typename Traits::template Writer<Value> >(id, value);
-    }
-
-    /// \brief Add an attribute writer command for the writer.
-    ///
-    /// Add an attribute writer command for the writer.
-    template <typename Writer, typename Value>
-    AttributeWriter& writeAttribute(const std::string& name, 
-				    const Value& value,
-				    const Writer& writer = Writer()) {
-      writers.push_back(make_pair(name, new ValueWriter<Value, Writer>
-      			       (value, writer)));
-      return *this;
-    }
-
-  protected:
-
-    /// \brief The header of section.
-    ///
-    /// It gives back the header of the section.
-    std::string header() {
-      return "@attributes " + id;
-    }
-
-    /// \brief  Writer function of the section.
-    ///
-    /// Write the content of the section.
-    void write(std::ostream& os) {
-      typename Writers::iterator it;
-      for (it = writers.begin(); it != writers.end(); ++it) {
-	os << it->first << ' ';
-	it->second->write(os);
-	os << std::endl;
-      }
-    }    
-
-  private:
-    std::string id;
-
-    typedef std::vector<std::pair<std::string, ValueWriterBase*> > Writers;
-    Writers writers;  
-  };
-
-
-}
-#endif