RhodeCode

/* -*- C++ -*-

 *

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

 *

 * Copyright (C) 2003-2008

 * 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 demos

///\file

///\brief Demonstrating graph input and output

///

/// This program gives an example of how to load a directed graph from

/// an \ref lgf-format "LGF" file with the \ref lemon::DigraphReader

/// "DigraphReader" class.

///

/// The \c "digraph.lgf" file:

/// \include digraph.lgf

///

/// And the program which reads it:

/// \include lgf_demo.cc

#include <iostream>

#include <lemon/smart_graph.h>

#include <lemon/lgf_reader.h>

#include <lemon/lgf_writer.h>

using namespace lemon;

int main() {

  SmartDigraph g;

  SmartDigraph::ArcMap<int> cap(g);

  SmartDigraph::Node s, t;

    arcMap("capacity", cap).       // read the 'capacity' arc map into cap

    node("source", s).             // read 'source' node to s

    node("target", t).             // read 'target' node to t

    run();

  std::cout << "Number of nodes: " << countNodes(g) << std::endl;

  std::cout << "Number of arcs: " << countArcs(g) << std::endl;

  std::cout << "We can write it to the standard output:" << std::endl;

  digraphWriter(std::cout, g).     // write g to the standard output

    arcMap("capacity", cap).       // write cap into 'capacity'

    node("source", s).             // write s to 'source'

    node("target", t).             // write t to 'target'

    run();

  return 0;

}

/**

@defgroup graph_prop Connectivity and other graph properties

@ingroup algs

\brief Algorithms for discovering the graph properties

This group describes the algorithms for discovering the graph properties

like connectivity, bipartiteness, euler property, simplicity etc.

\image html edge_biconnected_components.png

\image latex edge_biconnected_components.eps "bi-edge-connected components" width=\textwidth

*/

/**

@defgroup planar Planarity embedding and drawing

@ingroup algs

\brief Algorithms for planarity checking, embedding and drawing

This group describes the algorithms for planarity checking, embedding and drawing.

\image html planar.png

\image latex planar.eps "Plane graph" width=\textwidth

*/

/**

@defgroup matching Matching algorithms 

@ingroup algs

\brief Algorithms for finding matchings in graphs and bipartite graphs.

This group contains algorithm objects and functions to calculate

matchings in graphs and bipartite graphs. The general matching problem is

finding a subset of the arcs which does not shares common endpoints.

There are several different algorithms for calculate matchings in

graphs.  The matching problems in bipartite graphs are generally

easier than in general graphs. The goal of the matching optimization

can be the finding maximum cardinality, maximum weight or minimum cost

matching. The search can be constrained to find perfect or

maximum cardinality matching.

Lemon contains the next algorithms:

- \ref lemon::MaxBipartiteMatching "MaxBipartiteMatching" Hopcroft-Karp 

  augmenting path algorithm for calculate maximum cardinality matching in 

  bipartite graphs

- \ref lemon::PrBipartiteMatching "PrBipartiteMatching" Push-Relabel 

  algorithm for calculate maximum cardinality matching in bipartite graphs 

- \ref lemon::MaxWeightedBipartiteMatching "MaxWeightedBipartiteMatching" 

  Successive shortest path algorithm for calculate maximum weighted matching 

  and maximum weighted bipartite matching in bipartite graph

- \ref lemon::MinCostMaxBipartiteMatching "MinCostMaxBipartiteMatching" 

  Successive shortest path algorithm for calculate minimum cost maximum 

  matching in bipartite graph

- \ref lemon::MaxMatching "MaxMatching" Edmond's blossom shrinking algorithm

  for calculate maximum cardinality matching in general graph

- \ref lemon::MaxWeightedMatching "MaxWeightedMatching" Edmond's blossom

  shrinking algorithm for calculate maximum weighted matching in general

  graph

- \ref lemon::MaxWeightedPerfectMatching "MaxWeightedPerfectMatching"

  Edmond's blossom shrinking algorithm for calculate maximum weighted

  perfect matching in general graph

\image html bipartite_matching.png

\image latex bipartite_matching.eps "Bipartite Matching" width=\textwidth

*/

/**

@defgroup spantree Minimum Spanning Tree algorithms

@ingroup algs

\brief Algorithms for finding a minimum cost spanning tree in a graph.

This group describes the algorithms for finding a minimum cost spanning

tree in a graph

*/

/**

@defgroup auxalg Auxiliary algorithms

@ingroup algs

\brief Auxiliary algorithms implemented in LEMON.

This group describes some algorithms implemented in LEMON

in order to make it easier to implement complex algorithms.

*/

/**

@defgroup approx Approximation algorithms

\brief Approximation algorithms.

This group describes the approximation and heuristic algorithms

implemented in LEMON.

*/

/**

@defgroup gen_opt_group General Optimization Tools

\brief This group describes some general optimization frameworks

implemented in LEMON.

This group describes some general optimization frameworks

implemented in LEMON.

*/

/**

@defgroup lp_group Lp and Mip solvers

@ingroup gen_opt_group

\brief Lp and Mip solver interfaces for LEMON.

This group describes Lp and Mip solver interfaces for LEMON. The

various LP solvers could be used in the same manner with this

interface.

*/

/** 

@defgroup lp_utils Tools for Lp and Mip solvers 

@ingroup lp_group

\brief Helper tools to the Lp and Mip solvers.

This group adds some helper tools to general optimization framework

implemented in LEMON.

*/

/**

@defgroup metah Metaheuristics

@ingroup gen_opt_group

\brief Metaheuristics for LEMON library.

This group describes some metaheuristic optimization tools.

*/

/**

@defgroup utils Tools and Utilities 

\brief Tools and utilities for programming in LEMON

Tools and utilities for programming in LEMON.

*/

/**

@defgroup gutils Basic Graph Utilities

@ingroup utils

\brief Simple basic graph utilities.

This group describes some simple basic graph utilities.

*/

/**

@defgroup misc Miscellaneous Tools

@ingroup utils

\brief Tools for development, debugging and testing.

This group describes several useful tools for development,

debugging and testing.

*/

/**

@defgroup timecount Time measuring and Counting

@ingroup misc

\brief Simple tools for measuring the performance of algorithms.

This group describes simple tools for measuring the performance

of algorithms.

*/

/**

@defgroup graphbits Tools for Graph Implementation

@ingroup utils

\brief Tools to make it easier to create graphs.

This group describes the tools that makes it easier to create graphs and

the maps that dynamically update with the graph changes.

*/

/**

@defgroup exceptions Exceptions

@ingroup utils

\brief Exceptions defined in LEMON.

This group describes the exceptions defined in LEMON.

*/

/**

@defgroup io_group Input-Output

\brief Graph Input-Output methods

This group describes the tools for importing and exporting graphs 

and graph related data. Now it supports the LEMON format, the

\c DIMACS format and the encapsulated postscript (EPS) format.

*/

/**

@defgroup lemon_io Lemon Input-Output

@ingroup io_group

*/

/**

@defgroup eps_io Postscript exporting

@ingroup io_group

\brief General \c EPS drawer and graph exporter

This group describes general \c EPS drawing methods and special

graph exporting tools. 

*/

/**

@defgroup concept Concepts

\brief Skeleton classes and concept checking classes

This group describes the data/algorithm skeletons and concept checking

classes implemented in LEMON.

The purpose of the classes in this group is fourfold.

- These classes contain the documentations of the concepts. In order

  to avoid document multiplications, an implementation of a concept

  simply refers to the corresponding concept class.

- These classes declare every functions, <tt>typedef</tt>s etc. an

  implementation of the concepts should provide, however completely

  without implementations and real data structures behind the

  interface. On the other hand they should provide nothing else. All

  the algorithms working on a data structure meeting a certain concept

  should compile with these classes. (Though it will not run properly,

  of course.) In this way it is easily to check if an algorithm

  doesn't use any extra feature of a certain implementation.

- The concept descriptor classes also provide a <em>checker class</em>

  that makes it possible to check whether a certain implementation of a

  concept indeed provides all the required features.

- Finally, They can serve as a skeleton of a new implementation of a concept.

*/

/**

@defgroup graph_concepts Graph Structure Concepts

@ingroup concept

\brief Skeleton and concept checking classes for graph structures

This group describes the skeletons and concept checking classes of LEMON's

graph structures and helper classes used to implement these.

*/

/* --- Unused group

@defgroup experimental Experimental Structures and Algorithms

This group describes some Experimental structures and algorithms.

The stuff here is subject to change.

*/

/**

\anchor demoprograms

@defgroup demos Demo programs

Some demo programs are listed here. Their full source codes can be found in

the \c demo subdirectory of the source tree.

It order to compile them, use <tt>--enable-demo</tt> configure option when

build the library.

*/

/**

@defgroup tools Standalone utility applications

Some utility applications are listed here. 

The standard compilation procedure (<tt>./configure;make</tt>) will compile

them, as well. 

*/

/* -*- C++ -*-

 *

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

 *

 * Copyright (C) 2003-2008

 * 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.

 *

 */

namespace lemon {

/*!

\page lgf-format Lemon Graph Format (LGF)

The \e LGF is a <em>column oriented</em>

file format for storing graphs and associated data like

node and edge maps.

Each line with \c '#' first non-whitespace

character is considered as a comment line.

Otherwise the file consists of sections starting with

a header line. The header lines starts with an \c '@' character followed by the

type of section. The standard section types are \c \@nodes, \c

\@arcs and \c \@edges

and \@attributes. Each header line may also have an optional

\e name, which can be use to distinguish the sections of the same

type.

The standard sections are column oriented, each line consists of

<em>token</em>s separated by whitespaces. A token can be \e plain or

\e quoted. A plain token is just a sequence of non-whitespace characters,

while a quoted token is a

character sequence surrounded by double quotes, and it can also

contain whitespaces and escape sequences. 

The \c \@nodes section describes a set of nodes and associated

maps appearing in the following lines.

One of the maps must be called \c

"label", which plays special role in the file.

The following

non-empty lines until the next section describes nodes of the

graph. Each line contains the values of the node maps

associated to the current node.

\code

 @nodes

 label   coordinates size    title

 1       (10,20)     10      "First node"

 2       (80,80)     8       "Second node"

 3       (40,10)     10      "Third node"

\endcode

The \c \@arcs section is very similar to the \c \@nodes section,

but the \c "label" map is not obligatory here. The following lines

describe the arcs. The first two tokens of each line are

the source and the target node of the arc, respectively, then come the map

values. The source and target tokens must be node labels.

\code

 @arcs

 	      capacity

 1   2   16

 1   3   12

 2   3   18

\endcode

The \c \@edges is just a synonym of \c \@arcs.

The \c \@attributes section contains key-value pairs, each line

consists of two tokens, an attribute name, and then an attribute value.

\code

 @attributes

 source 1

 target 3

 caption "LEMON test digraph"

\endcode

The \e LGF can contain extra sections, but there is no restriction on

the format of such sections.

*/

}

//  LocalWords:  whitespace whitespaces

/* -*- C++ -*-

 *

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

 *

 * Copyright (C) 2003-2008

 * 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

#ifndef LEMON_LGF_READER_H

#define LEMON_LGF_READER_H

#include <iostream>

#include <fstream>

#include <sstream>

#include <set>

#include <map>

#include <lemon/assert.h>

#include <lemon/graph_utils.h>

#include <lemon/lgf_writer.h>

#include <lemon/concept_check.h>

#include <lemon/concepts/maps.h>

namespace lemon {

  namespace _reader_bits {

    template <typename Value>

    struct DefaultConverter {

      Value operator()(const std::string& str) {

	std::istringstream is(str);

	Value value;

	is >> value;

	char c;

	if (is >> std::ws >> c) {

	  throw DataFormatError("Remaining characters in token");

	}

	return value;

      }

    };

    template <>

    struct DefaultConverter<std::string> {

      std::string operator()(const std::string& str) {

	return str;

      }

    };

    template <typename _Item>    

    class MapStorageBase {

    public:

      typedef _Item Item;

    public:

      MapStorageBase() {}

      virtual ~MapStorageBase() {}

      virtual void set(const Item& item, const std::string& value) = 0;

    };

    template <typename _Item, typename _Map, 

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

    class MapStorage : public MapStorageBase<_Item> {

    public:

      typedef _Map Map;

      typedef _Converter Converter;

      typedef _Item Item;

    private:

      Map& _map;

      Converter _converter;

    public:

      MapStorage(Map& map, const Converter& converter = Converter()) 

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

      virtual ~MapStorage() {}

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

	_map.set(item, _converter(value));

      }

    };

    template <typename _Graph, bool _dir, typename _Map, 

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

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

    public:

      typedef _Map Map;

      typedef _Converter Converter;

      typedef _Graph Graph;

      typedef typename Graph::Edge Item;

      static const bool dir = _dir;

    private:

      const Graph& _graph;

      Map& _map;

      Converter _converter;

    public:

      GraphArcMapStorage(const Graph& graph, Map& map, 

			 const Converter& converter = Converter()) 

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

      virtual ~GraphArcMapStorage() {}

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

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

      }

    };

    class ValueStorageBase {

    public:

      ValueStorageBase() {}

      virtual ~ValueStorageBase() {}

      virtual void set(const std::string&) = 0;

    };

    template <typename _Value, typename _Converter = DefaultConverter<_Value> >

    class ValueStorage : public ValueStorageBase {

    public:

      typedef _Value Value;

      typedef _Converter Converter;

    private:

      Value& _value;

      Converter _converter;

    public:

      ValueStorage(Value& value, const Converter& converter = Converter())

 	: _value(value), _converter(converter) {}

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

	_value = _converter(value);

      }

    };

    template <typename Value>

    struct MapLookUpConverter {

      const std::map<std::string, Value>& _map;

      MapLookUpConverter(const std::map<std::string, Value>& map)

        : _map(map) {}

      Value operator()(const std::string& str) {

        typename std::map<std::string, Value>::const_iterator it =

          _map.find(str);

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

          std::ostringstream msg;

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

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

        }

        return it->second;

      }

    };

    template <typename Graph>

    struct GraphArcLookUpConverter {

      const Graph& _graph;

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

      GraphArcLookUpConverter(const Graph& graph, 

			      const std::map<std::string,

			                     typename Graph::Edge>& map) 

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

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

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

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

	}

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

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

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

	  throw DataFormatError("Item not found");

	}

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

      }

    };

    bool isWhiteSpace(char c) {

      return c == ' ' || c == '\t' || c == '\v' || 

        c == '\n' || c == '\r' || c == '\f'; 

    }

    bool isOct(char c) {

      return '0' <= c && c <='7'; 

    }

    int valueOct(char c) {

      LEMON_ASSERT(isOct(c), "The character is not octal.");

      return c - '0';

    }

    bool isHex(char c) {

      return ('0' <= c && c <= '9') || 

	('a' <= c && c <= 'z') || 

	('A' <= c && c <= 'Z'); 

    }

    int valueHex(char c) {

      LEMON_ASSERT(isHex(c), "The character is not hexadecimal.");

      if ('0' <= c && c <= '9') return c - '0';

      if ('a' <= c && c <= 'z') return c - 'a' + 10;

      return c - 'A' + 10;

    }

    bool isIdentifierFirstChar(char c) {

      return ('a' <= c && c <= 'z') ||

	('A' <= c && c <= 'Z') || c == '_';

    }

    bool isIdentifierChar(char c) {

      return isIdentifierFirstChar(c) ||

	('0' <= c && c <= '9');

    }

    char readEscape(std::istream& is) {

      char c;

      if (!is.get(c))

	throw DataFormatError("Escape format error");

      switch (c) {

      case '\\':

	return '\\';

      case '\"':

	return '\"';

      case '\'':

	return '\'';

      case '\?':

	return '\?';

      case 'a':

	return '\a';

      case 'b':

	return '\b';

      case 'f':

	return '\f';

      case 'n':

	return '\n';

      case 'r':

	return '\r';

      case 't':

	return '\t';

      case 'v':

	return '\v';

      case 'x':

	{

	  int code;

	  if (!is.get(c) || !isHex(c)) 

	    throw DataFormatError("Escape format error");

	  else if (code = valueHex(c), !is.get(c) || !isHex(c)) is.putback(c);

	  else code = code * 16 + valueHex(c);

	  return code;

	}

      default:

	{

	  int code;

	  if (!isOct(c)) 

	    throw DataFormatError("Escape format error");

	  else if (code = valueOct(c), !is.get(c) || !isOct(c)) 

	    is.putback(c);

	  else if (code = code * 8 + valueOct(c), !is.get(c) || !isOct(c)) 

	    is.putback(c);

	  else code = code * 8 + valueOct(c);

	  return code;

	}	      

      } 

    }

    std::istream& readToken(std::istream& is, std::string& str) {

      std::ostringstream os;

      char c;

      is >> std::ws;

      if (!is.get(c)) 

	return is;

      if (c == '\"') {

	while (is.get(c) && c != '\"') {

	  if (c == '\\') 

	    c = readEscape(is);

	  os << c;

	}

	if (!is) 

	  throw DataFormatError("Quoted format error");

      } else {

	is.putback(c);

	while (is.get(c) && !isWhiteSpace(c)) {

	  if (c == '\\') 

	    c = readEscape(is);

	  os << c;

	}

	if (!is) {

	  is.clear();

	} else {

	  is.putback(c);

	}

      }

      str = os.str();

      return is;

    }

    class Section {

    public:

      virtual ~Section() {}

      virtual void process(std::istream& is, int& line_num) = 0;

    };

    template <typename Functor>

    class LineSection : public Section {

    private:

      Functor _functor;

    public:

      LineSection(const Functor& functor) : _functor(functor) {}

      virtual ~LineSection() {}

      virtual void process(std::istream& is, int& line_num) {

	char c;

	std::string line;

	while (is.get(c) && c != '@') {

	  if (c == '\n') {

	    ++line_num;

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

	    getline(is, line);

	    ++line_num;

	  } else if (!isWhiteSpace(c)) {

	    is.putback(c);

	    getline(is, line);

	    _functor(line);

	    ++line_num;

	  }

	}

	if (is) is.putback(c);

	else if (is.eof()) is.clear();

      }

    };

    template <typename Functor>

    class StreamSection : public Section {

    private:

      Functor _functor;

    public:

      StreamSection(const Functor& functor) : _functor(functor) {}

      virtual ~StreamSection() {} 

      virtual void process(std::istream& is, int& line_num) {

	_functor(is, line_num);

	char c;

	std::string line;

	while (is.get(c) && c != '@') {

	  if (c == '\n') {

	    ++line_num;

	  } else if (!isWhiteSpace(c)) {

	    getline(is, line);

	    ++line_num;

	  }

	}

	if (is) is.putback(c);

	else if (is.eof()) is.clear();	

      }

    };

  }

  template <typename Digraph>

  class DigraphReader;

  template <typename Digraph>

  DigraphReader<Digraph> digraphReader(std::istream& is, Digraph& digraph);

  template <typename Digraph>

  DigraphReader<Digraph> digraphReader(const std::string& fn, Digraph& digraph);

  template <typename Digraph>

  DigraphReader<Digraph> digraphReader(const char *fn, Digraph& digraph);

  /// \ingroup lemon_io

  ///  

  ///

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

  ///

  /// The reading method does a batch processing. The user creates a

  /// reader object, then various reading rules can be added to the

  /// reader, and eventually the reading is executed with the \c run()

  /// member function. A map reading rule can be added to the reader

  /// with the \c nodeMap() or \c arcMap() members. An optional

  /// converter parameter can also be added as a standard functor

  /// is set, it will determine how the tokens in the file should be

  /// then a default conversion will be used. One map can be read into

  /// multiple map objects at the same time. The \c attribute(), \c

  /// node() and \c arc() functions are used to add attribute reading

  /// rules.

  ///

  ///\code

  ///\endcode

  ///

  /// By default the reader uses the first section in the file of the

  /// proper type. If a section has an optional name, then it can be

  /// selected for reading by giving an optional name parameter to the

  /// \c nodes(), \c arcs() or \c attributes() functions.

  ///

  /// The \c useNodes() and \c useArcs() functions are used to tell the reader

  /// that the nodes or arcs should not be constructed (added to the

  /// graph) during the reading, but instead the label map of the items

  /// are given as a parameter of these functions. An

  /// of the arc sets, while the second phase would read the second arc

  /// set into an \e ArcSet class (\c SmartArcSet or \c ListArcSet).

  /// The previously read label node map should be passed to the \c

  /// useNodes() functions. Another application of multipass reading when

  /// a single pass, because the arcs are not constructed when the node

  /// maps are read.

  template <typename _Digraph>

  class DigraphReader {

  public:

    typedef _Digraph Digraph;

    TEMPLATE_DIGRAPH_TYPEDEFS(Digraph);

  private:

    std::istream* _is;

    bool local_is;

    Digraph& _digraph;

    std::string _nodes_caption;

    std::string _arcs_caption;

    std::string _attributes_caption;

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

    NodeIndex _node_index;

    typedef std::map<std::string, Arc> ArcIndex;

    ArcIndex _arc_index;

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

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

    NodeMaps _node_maps; 

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

      _reader_bits::MapStorageBase<Arc>*> >ArcMaps;

    ArcMaps _arc_maps;

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

      Attributes;

    Attributes _attributes;

    bool _use_nodes;

    bool _use_arcs;

    bool _skip_nodes;

    bool _skip_arcs;

    int line_num;

    std::istringstream line;

  public:

    /// \brief Constructor

    ///

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

    /// input stream.

    DigraphReader(std::istream& is, Digraph& digraph) 

      : _is(&is), local_is(false), _digraph(digraph),

	_use_nodes(false), _use_arcs(false),

	_skip_nodes(false), _skip_arcs(false) {}

    /// \brief Constructor

    ///

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

    /// file.

    DigraphReader(const std::string& fn, Digraph& digraph) 

      : _is(new std::ifstream(fn.c_str())), local_is(true), _digraph(digraph),

    	_use_nodes(false), _use_arcs(false),

	_skip_nodes(false), _skip_arcs(false) {}

    /// \brief Constructor

    ///

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

    /// file.

    DigraphReader(const char* fn, Digraph& digraph) 

      : _is(new std::ifstream(fn)), local_is(true), _digraph(digraph),

    	_use_nodes(false), _use_arcs(false),

	_skip_nodes(false), _skip_arcs(false) {}

    /// \brief Destructor

    ~DigraphReader() {

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

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

	delete it->second;

      }

      for (typename ArcMaps::iterator it = _arc_maps.begin(); 

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

	delete it->second;

      }

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

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

	delete it->second;

      }

      if (local_is) {

	delete _is;

      }

    }

  private:

    friend DigraphReader<Digraph> digraphReader<>(std::istream& is, 

						  Digraph& digraph);    

    friend DigraphReader<Digraph> digraphReader<>(const std::string& fn, 

						  Digraph& digraph);   

    friend DigraphReader<Digraph> digraphReader<>(const char *fn, 

						  Digraph& digraph);    

    DigraphReader(DigraphReader& other) 

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

	_use_nodes(other._use_nodes), _use_arcs(other._use_arcs),

	_skip_nodes(other._skip_nodes), _skip_arcs(other._skip_arcs) {

      other._is = 0;

      other.local_is = false;

      _node_index.swap(other._node_index);

      _arc_index.swap(other._arc_index);

      _node_maps.swap(other._node_maps);

      _arc_maps.swap(other._arc_maps);

      _attributes.swap(other._attributes);

      _nodes_caption = other._nodes_caption;

      _arcs_caption = other._arcs_caption;

      _attributes_caption = other._attributes_caption;

    }

    DigraphReader& operator=(const DigraphReader&);

  public:

    /// \name Reading rules

    /// @{

    /// \brief Node map reading rule

    ///

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

    template <typename Map>

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

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

      _reader_bits::MapStorageBase<Node>* storage = 

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

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

      return *this;

    }

    /// \brief Node map reading rule

    ///

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

    /// reader.

    template <typename Map, typename Converter>

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

			   const Converter& converter = Converter()) {

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

      _reader_bits::MapStorageBase<Node>* storage = 

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

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

      return *this;

    }

    /// \brief Arc map reading rule

    ///

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

    template <typename Map>

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

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

      _reader_bits::MapStorageBase<Arc>* storage = 

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

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

      return *this;

    }

    /// \brief Arc map reading rule

    ///

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

    /// reader.

    template <typename Map, typename Converter>

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

			  const Converter& converter = Converter()) {

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

      _reader_bits::MapStorageBase<Arc>* storage = 

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

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

      return *this;

    }

    /// \brief Attribute reading rule