/* -*- 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

///\brief Lemon Graph Format reader.

#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));

      }

    };

    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;

      }

    };

    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;

    }

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

      std::ostringstream os;

      char c;

      is >> std::ws;

      if (!is.get(c))

	return is;

      if (!isIdentifierFirstChar(c))

	throw DataFormatError("Wrong char in identifier");

      os << c;

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

	if (!isIdentifierChar(c)) 

	  throw DataFormatError("Wrong char in identifier");	  

	os << c;

      }

      if (!is) is.clear();

      str = os.str();

      return is;

    }

  }

  /// \e

  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;

    int line_num;

    std::istringstream line;

  public:

    /// \e

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

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

	_use_nodes(false), _use_arcs(false) {}

    /// \e

    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) {}

    /// \e

    DigraphReader(const char* fn, Digraph& digraph) 

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

    	_use_nodes(false), _use_arcs(false) {}

    /// \e

    DigraphReader(DigraphReader& other) 

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

	_use_nodes(other._use_nodes), _use_arcs(other._use_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;

    }

    /// \e

    ~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:

    DigraphReader& operator=(const DigraphReader&);

  public:

    /// \e

    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;

    }

    /// \e

    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;

    }

    /// \e

    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;

    }

    /// \e

    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;

    }

    /// \e

    template <typename Value>

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

      _reader_bits::ValueStorageBase* storage = 

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

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

      return *this;

    }

    /// \e

    template <typename Value, typename Converter>

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

			     const Converter& converter = Converter()) {

      _reader_bits::ValueStorageBase* storage = 

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

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

      return *this;

    }

    /// \e

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

      typedef _reader_bits::MapLookUpConverter<Node> Converter;

      Converter converter(_node_index);

      _reader_bits::ValueStorageBase* storage = 

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

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

      return *this;

    }

    /// \e

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

      typedef _reader_bits::MapLookUpConverter<Arc> Converter;

      Converter converter(_arc_index);

      _reader_bits::ValueStorageBase* storage = 

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

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

      return *this;

    }

    /// \e

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

      _nodes_caption = caption;

      return *this;

    }

    /// \e

    DigraphReader& arcs(const std::string& caption) {

      _arcs_caption = caption;

      return *this;

    }

    /// \e

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

      _attributes_caption = caption;

      return *this;

    }

    /// \e

    template <typename Map>

    DigraphReader& useNodes(const Map& map) {

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

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

      _use_nodes = true;

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

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

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

      }

      return *this;

    }

    /// \e

    template <typename Map, typename Converter>

    DigraphReader& useNodes(const Map& map, 

			    const Converter& converter = Converter()) {

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

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

      _use_nodes = true;

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

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

      }

      return *this;

    }

    /// \e

    template <typename Map>

    DigraphReader& useArcs(const Map& map) {

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

      LEMON_ASSERT(!_use_arcs, "Multiple usage of useArcs() member");

      _use_arcs = true;

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

      for (ArcIt a(_digraph); a != INVALID; ++a) {

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

      }

      return *this;

    }

    /// \e

    template <typename Map, typename Converter>

    DigraphReader& useArcs(const Map& map, 

			    const Converter& converter = Converter()) {

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

      LEMON_ASSERT(!_use_arcs, "Multiple usage of useArcs() member"); 

      _use_arcs = true;

      for (ArcIt a(_digraph); a != INVALID; ++a) {

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

      }

      return *this;

    }

  private:

    bool readLine() {

      std::string str;

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

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

	char c;

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

	  line.putback(c);

	  return true;

	}

      }

      return false;

    }

    bool readSuccess() {

      return static_cast<bool>(*_is);

    }

    void skipSection() {

      char c;

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

	readLine();

      }

      line.putback(c);

    }

    void readNodes() {

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

      int map_num, label_index;

      if (!readLine()) 

	throw DataFormatError("Cannot find map captions");

      {

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

	std::string map;

	int index = 0;

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

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

	    std::ostringstream msg;

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

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

	  }

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

	  ++index;

	}

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

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

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

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

	    std::ostringstream msg;

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

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

	  }

	  map_index[i] = jt->second;

	}

	{

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

	  if (jt == maps.end())

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

	  label_index = jt->second;

	}

	map_num = maps.size();

      }

      char c;

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

	line.putback(c);

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

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

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

	    std::ostringstream msg;

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

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

	  }

	}

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

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

	Node n;

	if (!_use_nodes) {

	  n = _digraph.addNode();

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

	} else {

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

	    _node_index.find(tokens[label_index]);

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

	    std::ostringstream msg;

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

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

	  }

	  n = it->second;

	}

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

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

	}

      }

      if (readSuccess()) {

	line.putback(c);

      }

    }

    void readArcs() {

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

      int map_num, label_index;

      if (!readLine()) 

	throw DataFormatError("Cannot find map captions");

      {

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

	std::string map;

	int index = 0;

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

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

	    std::ostringstream msg;

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

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

	  }

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

	  ++index;

	}

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

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

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

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

	    std::ostringstream msg;

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

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

	  }

	  map_index[i] = jt->second;

	}

	{

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

	  if (jt == maps.end())

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

	  label_index = jt->second;

	}

	map_num = maps.size();

      }

      char c;

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

	line.putback(c);

	std::string source_token;

	std::string target_token;

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

	  throw DataFormatError("Source not found");

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

	  throw DataFormatError("Source not found");

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

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

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

	    std::ostringstream msg;

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

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

	  }

	}

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

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

	Arc a;

	if (!_use_arcs) {

          typename NodeIndex::iterator it;

          it = _node_index.find(source_token);

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

            std::ostringstream msg;

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

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

          }

          Node source = it->second;

          it = _node_index.find(target_token);

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

            std::ostringstream msg;            

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

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

          }                                          

          Node target = it->second;                            

	  a = _digraph.addArc(source, target);

	  _arc_index.insert(std::make_pair(tokens[label_index], a));

	} else {

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

	    _arc_index.find(tokens[label_index]);

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

	    std::ostringstream msg;

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

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

	  }

	  a = it->second;

	}

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

	  _arc_maps[i].second->set(a, tokens[map_index[i]]);

	}

      }

      if (readSuccess()) {

	line.putback(c);

      }

    }

    void readAttributes() {

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

      char c;

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

	line.putback(c);

	std::string attr, token;

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

	  throw DataFormatError("Attribute name not found");

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

	  throw DataFormatError("Attribute value not found");

	if (line >> c)

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

	{

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

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

	    std::ostringstream msg;

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

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

	  }

	  read_attr.insert(attr);

	}

	{

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

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

	    it->second->set(token);

	    ++it;

	  }

	}

      }

      if (readSuccess()) {

	line.putback(c);

      }

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

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

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

	  std::ostringstream msg;

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

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

	}	

      }

    }

  public:

    /// \e

    void run() {

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

      bool nodes_done = false;

      bool arcs_done = false;

      bool attributes_done = false;

      line_num = 0;      

      readLine();

      while (readSuccess()) {

	skipSection();

	try {

	  char c;

	  std::string section, caption;

	  line >> c;

	  _reader_bits::readIdentifier(line, section);

	  _reader_bits::readIdentifier(line, caption);

	  if (line >> c) 

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

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

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

	      readNodes();

	      nodes_done = true;

	    }

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

		     !arcs_done) {

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

	      readArcs();

	      arcs_done = true;

	    }

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

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

	      readAttributes();

	      attributes_done = true;

	    }

	  } else {

	    readLine();

	    skipSection();

	  }

	} catch (DataFormatError& error) {

	  error.line(line_num);

	  throw;

	}	

      }

      if (!nodes_done) {

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

      }

      if (!arcs_done) {

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

      }

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

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

      }

    }

  };

  template <typename Digraph>

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

    return DigraphReader<Digraph>(is, digraph);

  }

  template <typename Digraph>

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

				       Digraph& digraph) {

    return DigraphReader<Digraph>(fn, digraph);

  }

  template <typename Digraph>

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

    return DigraphReader<Digraph>(fn, digraph);

  }

}

#endif