lemon/iterable_maps.h
author deba
Tue, 31 Jan 2006 20:04:36 +0000
changeset 1933 a876a3d6a4c7
parent 1913 49fe71fce7fb
child 1953 d4f411003580
permissions -rw-r--r--
Revising the bpugraph concept

We need a public but very limited ANode and BNode class
It can be used with ItemSetTraits and with some special maps

By example:
DescriptorMap<Graph, ANode>
InvertableMap<Graph, ANode, string>
IterableBoolMap<Graph, ANode>
IterableIntMap<Graph, ANode>
IterableValueMap<Graph, ANode, string>
     1 /* -*- C++ -*-
     2  * lemon/iterable_maps.h - Part of LEMON, a generic C++ optimization library
     3  *
     4  * Copyright (C) 2006 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
     5  * (Egervary Research Group on Combinatorial Optimization, EGRES).
     6  *
     7  * Permission to use, modify and distribute this software is granted
     8  * provided that this copyright notice appears in all copies. For
     9  * precise terms see the accompanying LICENSE file.
    10  *
    11  * This software is provided "AS IS" with no warranty of any kind,
    12  * express or implied, and with no claim as to its suitability for any
    13  * purpose.
    14  *
    15  */
    16 
    17 #include <lemon/traits.h>
    18 #include <lemon/invalid.h>
    19 
    20 #include <vector>
    21 #include <map>
    22 
    23 #include <iterator>
    24 #include <limits>
    25 
    26 ///\ingroup maps
    27 ///\file
    28 ///\brief Maps that makes it possible to iterate through the keys having
    29 ///a certain value
    30 ///
    31 ///
    32 
    33 
    34 namespace lemon {
    35 
    36   ///\ingroup graph_maps
    37   ///
    38   /// \brief Dynamic iterable bool map.
    39   ///
    40   /// This class provides a special graph map type which can store
    41   /// for each graph item(node, edge, etc.) a bool value. For both 
    42   /// the true and the false it is possible to iterate on the keys which
    43   /// mapped to the given value.
    44   /// 
    45   /// \param _Graph The graph type.
    46   /// \param _Item One of the graph's item type, the key of the map.
    47   template <typename _Graph, typename _Item>
    48   class IterableBoolMap 
    49     : protected ItemSetTraits<_Graph, _Item>::template Map<int>::Parent {
    50   private:
    51     typedef _Graph Graph;
    52     
    53     typedef typename ItemSetTraits<Graph, _Item>::ItemIt KeyIt;
    54     typedef typename ItemSetTraits<Graph, _Item>
    55     ::template Map<int>::Parent Parent;
    56     
    57     std::vector<_Item> array;
    58     int sep;
    59 
    60     const Graph& graph;
    61 
    62   public:
    63 
    64     /// Indicates that the map if reference map.
    65     typedef True ReferenceMapTag;
    66 
    67     /// The key type
    68     typedef _Item Key;
    69     /// The value type
    70     typedef bool Value;
    71     /// The const reference type.    
    72     typedef const Value& ConstReference;
    73 
    74   private:
    75 
    76     int position(const Key& key) const {
    77       return Parent::operator[](key);
    78     }
    79 
    80   public:
    81 
    82     /// \brief Refernce to the value of the map.
    83     ///
    84     /// This class is near to similar to the bool type. It can
    85     /// be converted to bool and it has the same operators.
    86     class Reference {
    87       friend class IterableBoolMap;
    88     private:
    89       Reference(IterableBoolMap& map, const Key& key) 
    90 	: _key(key), _map(map) {} 
    91     public:
    92 
    93       Reference& operator=(const Reference& value) {
    94 	_map.set(_key, (bool)value);
    95  	return *this;
    96       }
    97 
    98       operator bool() const { 
    99 	return static_cast<const IterableBoolMap&>(_map)[_key]; 
   100       }
   101 
   102       Reference& operator=(bool value) { 
   103 	_map.set(_key, value); 
   104 	return *this; 
   105       }
   106       Reference& operator&=(bool value) {
   107 	_map.set(_key, _map[_key] & value); 
   108 	return *this; 	
   109       }
   110       Reference& operator|=(bool value) {
   111 	_map.set(_key, _map[_key] | value); 
   112 	return *this; 	
   113       }
   114       Reference& operator^=(bool value) {
   115 	_map.set(_key, _map[_key] ^ value); 
   116 	return *this; 	
   117       }
   118     private:
   119       Key _key;
   120       IterableBoolMap& _map; 
   121     };
   122     
   123     /// \brief Constructor of the Map with a default value.
   124     ///
   125     /// Constructor of the Map with a default value.
   126     IterableBoolMap(const Graph& _graph, bool def = false) 
   127       : Parent(_graph), graph(_graph) {
   128       for (KeyIt it(graph); it != INVALID; ++it) {
   129         Parent::set(it, array.size());
   130         array.push_back(it);
   131       }
   132       sep = (def ? array.size() : 0);
   133     }
   134 
   135     /// \brief Const subscript operator of the map.
   136     ///
   137     /// Const subscript operator of the map.
   138     bool operator[](const Key& key) const {
   139       return position(key) < sep;
   140     }
   141 
   142     /// \brief Subscript operator of the map.
   143     ///
   144     /// Subscript operator of the map.
   145     Reference operator[](const Key& key) {
   146       return Reference(*this, key);
   147     }
   148 
   149     /// \brief Set operation of the map.
   150     ///
   151     /// Set operation of the map.
   152     void set(const Key& key, bool value) {
   153       int pos = position(key);
   154       if (value) {
   155         if (pos < sep) return;
   156         Key tmp = array[sep];
   157         array[sep] = key;
   158         Parent::set(key, sep);
   159         array[pos] = tmp;
   160         Parent::set(tmp, pos); 
   161         ++sep;
   162       } else {
   163         if (pos >= sep) return;
   164         --sep;
   165         Key tmp = array[sep];
   166         array[sep] = key;
   167         Parent::set(key, sep);
   168         array[pos] = tmp;
   169         Parent::set(tmp, pos);
   170       }
   171     }
   172 
   173     /// \brief Returns the number of the keys mapped to true.
   174     ///
   175     /// Returns the number of the keys mapped to true.
   176     int trueNum() const {
   177       return sep;
   178     } 
   179     
   180     /// \brief Returns the number of the keys mapped to false.
   181     ///
   182     /// Returns the number of the keys mapped to false.
   183     int falseNum() const {
   184       return array.size() - sep;
   185     }
   186 
   187     /// \brief Iterator for the keys mapped to true.
   188     ///
   189     /// Iterator for the keys mapped to true. It works
   190     /// like a graph item iterator in the map, it can be converted
   191     /// the key type of the map, incremented with \c ++ operator, and
   192     /// if the iterator leave the last valid key it will be equal to 
   193     /// \c INVALID.
   194     class TrueIt : public Key {
   195     public:
   196       typedef Key Parent;
   197       
   198       /// \brief Creates an iterator.
   199       ///
   200       /// Creates an iterator. It iterates on the 
   201       /// keys which mapped to true.
   202       /// \param map The IterableIntMap
   203       TrueIt(const IterableBoolMap& _map) 
   204         : Parent(_map.sep > 0 ? _map.array[_map.sep - 1] : INVALID), 
   205           map(&_map) {}
   206 
   207       /// \brief Invalid constructor \& conversion.
   208       ///
   209       /// This constructor initializes the key to be invalid.
   210       /// \sa Invalid for more details.
   211       TrueIt(Invalid) : Parent(INVALID), map(0) {}
   212 
   213       /// \brief Increment operator.
   214       ///
   215       /// Increment Operator.
   216       TrueIt& operator++() {
   217         int pos = map->position(*this);
   218         Parent::operator=(pos > 0 ? map->array[pos - 1] : INVALID);
   219         return *this;
   220       }
   221 
   222       
   223     private:
   224       const IterableBoolMap* map;
   225     };
   226 
   227     /// \brief Iterator for the keys mapped to false.
   228     ///
   229     /// Iterator for the keys mapped to false. It works
   230     /// like a graph item iterator in the map, it can be converted
   231     /// the key type of the map, incremented with \c ++ operator, and
   232     /// if the iterator leave the last valid key it will be equal to 
   233     /// \c INVALID.
   234     class FalseIt : public Key {
   235     public:
   236       typedef Key Parent;
   237       
   238       /// \brief Creates an iterator.
   239       ///
   240       /// Creates an iterator. It iterates on the 
   241       /// keys which mapped to false.
   242       /// \param map The IterableIntMap
   243       FalseIt(const IterableBoolMap& _map) 
   244         : Parent(_map.sep < (int)_map.array.size() ? 
   245                  _map.array.back() : INVALID), map(&_map) {}
   246 
   247       /// \brief Invalid constructor \& conversion.
   248       ///
   249       /// This constructor initializes the key to be invalid.
   250       /// \sa Invalid for more details.
   251       FalseIt(Invalid) : Parent(INVALID), map(0) {}
   252 
   253       /// \brief Increment operator.
   254       ///
   255       /// Increment Operator.
   256       FalseIt& operator++() {
   257         int pos = map->position(*this);
   258         Parent::operator=(pos > map->sep ? map->array[pos - 1] : INVALID);
   259         return *this;
   260       }
   261 
   262     private:
   263       const IterableBoolMap* map;
   264     };
   265 
   266     /// \brief Iterator for the keys mapped to a given value.
   267     ///
   268     /// Iterator for the keys mapped to a given value. It works
   269     /// like a graph item iterator in the map, it can be converted
   270     /// the key type of the map, incremented with \c ++ operator, and
   271     /// if the iterator leave the last valid key it will be equal to 
   272     /// \c INVALID.
   273     class ItemIt : public Key {
   274     public:
   275       typedef Key Parent;
   276       
   277       /// \brief Creates an iterator.
   278       ///
   279       /// Creates an iterator. It iterates on the 
   280       /// keys which mapped to false.
   281       /// \param map The IterableIntMap
   282       /// \param value Which elements should be iterated.
   283       ItemIt(const IterableBoolMap& _map, bool value) 
   284         : Parent(value ? (_map.sep > 0 ? _map.array[_map.sep - 1] : INVALID) :
   285                  (_map.sep < (int)_map.array.size() ? 
   286                   _map.array.back() : INVALID)), map(&_map) {}
   287 
   288       /// \brief Invalid constructor \& conversion.
   289       ///
   290       /// This constructor initializes the key to be invalid.
   291       /// \sa Invalid for more details.
   292       ItemIt(Invalid) : Parent(INVALID), map(0) {}
   293 
   294       /// \brief Increment operator.
   295       ///
   296       /// Increment Operator.
   297       ItemIt& operator++() {
   298         int pos = map->position(*this);
   299         int sep = pos >= map->sep ? map->sep : 0;
   300         Parent::operator=(pos > sep ? map->array[pos - 1] : INVALID);
   301         return *this;
   302       }
   303 
   304     private:
   305       const IterableBoolMap* map;
   306     };
   307 
   308   protected:
   309     
   310     virtual void add(const Key& key) {
   311       Parent::add(key);
   312       Parent::set(key, array.size());
   313       array.push_back(key);
   314     }
   315 
   316     virtual void add(const std::vector<Key>& keys) {
   317       Parent::add(keys);
   318       for (int i = 0; i < (int)keys.size(); ++i) {
   319         Parent::set(keys[i], array.size());
   320         array.push_back(keys[i]);
   321       }
   322     }
   323 
   324     virtual void erase(const Key& key) {
   325       int pos = position(key); 
   326       if (pos < sep) {
   327         --sep;
   328         Parent::set(array[sep], pos);
   329         array[pos] = array[sep];
   330         Parent::set(array.back(), sep);
   331         array[sep] = array.back();
   332         array.pop_back();
   333       } else {
   334         Parent::set(array.back(), pos);
   335         array[pos] = array.back();
   336         array.pop_back();
   337       }
   338       Parent::erase(key);
   339     }
   340 
   341     virtual void erase(const std::vector<Key>& keys) {
   342       for (int i = 0; i < (int)keys.size(); ++i) {
   343         int pos = position(keys[i]); 
   344         if (pos < sep) {
   345           --sep;
   346           Parent::set(array[sep], pos);
   347           array[pos] = array[sep];
   348           Parent::set(array.back(), sep);
   349           array[sep] = array.back();
   350           array.pop_back();
   351         } else {
   352           Parent::set(array.back(), pos);
   353           array[pos] = array.back();
   354           array.pop_back();
   355         }
   356       }
   357       Parent::erase(keys);
   358     }    
   359 
   360     virtual void build() {
   361       Parent::build();
   362       for (KeyIt it(graph); it != INVALID; ++it) {
   363         Parent::set(it, array.size());
   364         array.push_back(it);
   365       }
   366       sep = 0;      
   367     }
   368 
   369     virtual void clear() {
   370       array.clear();
   371       sep = 0;
   372       Parent::clear();
   373     }
   374     
   375   };
   376   
   377 
   378   namespace _iterable_maps_bits {
   379     template <typename Item>
   380     struct IterableIntMapNode {
   381       IterableIntMapNode() : value(-1) {}
   382       IterableIntMapNode(int _value) : value(_value) {}
   383       Item prev, next;
   384       int value;
   385     };
   386   }
   387 
   388   ///\ingroup graph_maps
   389   ///
   390   /// \brief Dynamic iterable integer map.
   391   ///
   392   /// This class provides a special graph map type which can store
   393   /// for each graph item(node, edge, etc.) an integer value. For each
   394   /// non negative value it is possible to iterate on the keys which
   395   /// mapped to the given value.
   396   /// 
   397   /// \param _Graph The graph type.
   398   /// \param _Item One of the graph's item type, the key of the map.
   399   template <typename _Graph, typename _Item>
   400   class IterableIntMap : protected ItemSetTraits<_Graph, _Item> 
   401   ::template Map<_iterable_maps_bits::IterableIntMapNode<_Item> >::Parent {
   402   public:
   403     typedef typename ItemSetTraits<_Graph, _Item> 
   404     ::template Map<_iterable_maps_bits::IterableIntMapNode<_Item> >
   405     ::Parent Parent;
   406 
   407     /// The key type
   408     typedef _Item Key;
   409     /// The value type
   410     typedef int Value;
   411     /// The graph type
   412     typedef _Graph Graph;
   413 
   414     /// \brief Constructor of the Map.
   415     ///
   416     /// Constructor of the Map. It set all values -1.
   417     explicit IterableIntMap(const Graph& graph) 
   418       : Parent(graph) {}
   419 
   420     /// \brief Constructor of the Map with a given value.
   421     ///
   422     /// Constructor of the Map with a given value.
   423     explicit IterableIntMap(const Graph& graph, int value) 
   424       : Parent(graph, _iterable_maps_bits::IterableIntMapNode<_Item>(value)) {
   425       if (value >= 0) {
   426 	for (typename Parent::ItemIt it(*this); it != INVALID; ++it) {
   427 	  lace(it);
   428 	}
   429       }
   430     }
   431 
   432   private:
   433     
   434     void unlace(const Key& key) {
   435       typename Parent::Value& node = Parent::operator[](key);
   436       if (node.value < 0) return;
   437       if (node.prev != INVALID) {
   438 	Parent::operator[](node.prev).next = node.next;	
   439       } else {
   440 	first[node.value] = node.next;
   441       }
   442       if (node.next != INVALID) {
   443 	Parent::operator[](node.next).prev = node.prev;
   444       }
   445       while (!first.empty() && first.back() == INVALID) {
   446 	first.pop_back();
   447       }
   448     }
   449 
   450     void lace(const Key& key) {
   451       typename Parent::Value& node = Parent::operator[](key);
   452       if (node.value < 0) return;
   453       if (node.value >= (int)first.size()) {
   454 	first.resize(node.value + 1, INVALID);
   455       } 
   456       node.prev = INVALID;
   457       node.next = first[node.value];
   458       if (node.next != INVALID) {
   459 	Parent::operator[](node.next).prev = key;	
   460       }
   461       first[node.value] = key;
   462     }
   463 
   464   public:
   465 
   466     /// Indicates that the map if reference map.
   467     typedef True ReferenceMapTag;
   468 
   469     /// \brief Refernce to the value of the map.
   470     ///
   471     /// This class is near to similar to the int type. It can
   472     /// be converted to int and it has the same operators.
   473     class Reference {
   474       friend class IterableIntMap;
   475     private:
   476       Reference(IterableIntMap& map, const Key& key) 
   477 	: _key(key), _map(map) {} 
   478     public:
   479 
   480       Reference& operator=(const Reference& value) {
   481 	_map.set(_key, (const int&)value);
   482  	return *this;
   483       }
   484 
   485       operator const int&() const { 
   486 	return static_cast<const IterableIntMap&>(_map)[_key]; 
   487       }
   488 
   489       Reference& operator=(int value) { 
   490 	_map.set(_key, value); 
   491 	return *this; 
   492       }
   493       Reference& operator++() {
   494 	_map.set(_key, _map[_key] + 1); 
   495 	return *this; 	
   496       }
   497       int operator++(int) {
   498 	int value = _map[_key];
   499 	_map.set(_key, value + 1); 
   500 	return value; 	
   501       }
   502       Reference& operator--() {
   503 	_map.set(_key, _map[_key] - 1); 
   504 	return *this; 	
   505       }
   506       int operator--(int) {
   507 	int value = _map[_key];
   508 	_map.set(_key, value - 1); 
   509 	return value; 	
   510       }
   511       Reference& operator+=(int value) { 
   512 	_map.set(_key, _map[_key] + value); 
   513 	return *this;
   514       }
   515       Reference& operator-=(int value) { 
   516 	_map.set(_key, _map[_key] - value); 
   517 	return *this;
   518       }
   519       Reference& operator*=(int value) { 
   520 	_map.set(_key, _map[_key] * value); 
   521 	return *this;
   522       }
   523       Reference& operator/=(int value) { 
   524 	_map.set(_key, _map[_key] / value); 
   525 	return *this;
   526       }
   527       Reference& operator%=(int value) { 
   528 	_map.set(_key, _map[_key] % value); 
   529 	return *this;
   530       }
   531       Reference& operator&=(int value) { 
   532 	_map.set(_key, _map[_key] & value); 
   533 	return *this;
   534       }
   535       Reference& operator|=(int value) { 
   536 	_map.set(_key, _map[_key] | value); 
   537 	return *this;
   538       }
   539       Reference& operator^=(int value) { 
   540 	_map.set(_key, _map[_key] ^ value); 
   541 	return *this;
   542       }
   543       Reference& operator<<=(int value) { 
   544 	_map.set(_key, _map[_key] << value); 
   545 	return *this;
   546       }
   547       Reference& operator>>=(int value) { 
   548 	_map.set(_key, _map[_key] >> value); 
   549 	return *this;
   550       }
   551 
   552     private:
   553       Key _key;
   554       IterableIntMap& _map; 
   555     };
   556 
   557     /// The const reference type.    
   558     typedef const Value& ConstReference;
   559 
   560     /// \brief Gives back the maximal value plus one.
   561     ///
   562     /// Gives back the maximal value plus one.
   563     unsigned int size() const {
   564       return first.size();
   565     }
   566     
   567     /// \brief Set operation of the map.
   568     ///
   569     /// Set operation of the map.
   570     void set(const Key& key, const Value& value) {
   571       unlace(key);
   572       Parent::operator[](key).value = value;
   573       lace(key);
   574     }
   575 
   576     /// \brief Const subscript operator of the map.
   577     ///
   578     /// Const subscript operator of the map.
   579     const Value& operator[](const Key& key) const {
   580       return Parent::operator[](key).value;
   581     }
   582 
   583     /// \brief Subscript operator of the map.
   584     ///
   585     /// Subscript operator of the map.
   586     Reference operator[](const Key& key) {
   587       return Reference(*this, key);
   588     }
   589 
   590     /// \brief Iterator for the keys with the same value.
   591     ///
   592     /// Iterator for the keys with the same value. It works
   593     /// like a graph item iterator in the map, it can be converted
   594     /// the item type of the map, incremented with \c ++ operator, and
   595     /// if the iterator leave the last valid item it will be equal to 
   596     /// \c INVALID.
   597     class ItemIt : public _Item {
   598     public:
   599       typedef _Item Parent;
   600 
   601       /// \brief Invalid constructor \& conversion.
   602       ///
   603       /// This constructor initializes the item to be invalid.
   604       /// \sa Invalid for more details.
   605       ItemIt(Invalid) : Parent(INVALID), _map(0) {}
   606 
   607       /// \brief Creates an iterator with a value.
   608       ///
   609       /// Creates an iterator with a value. It iterates on the 
   610       /// keys which have the given value.
   611       /// \param map The IterableIntMap
   612       /// \param value The value
   613       ItemIt(const IterableIntMap& map, int value) : _map(&map) {
   614 	if (value < 0 || value >= (int)_map->first.size()) {	  
   615 	  Parent::operator=(INVALID);
   616 	} else {
   617 	  Parent::operator=(_map->first[value]);
   618 	}
   619       } 
   620 
   621       /// \brief Increment operator.
   622       ///
   623       /// Increment Operator.
   624       ItemIt& operator++() {
   625 	Parent::operator=(_map->IterableIntMap::Parent::
   626 			  operator[](static_cast<Parent&>(*this)).next);
   627 	return *this;
   628       }
   629 
   630 
   631     private:
   632       const IterableIntMap* _map;
   633     };
   634 
   635   protected:
   636     
   637     virtual void erase(const Key& key) {
   638       unlace(key);
   639       Parent::erase(key);
   640     }
   641 
   642     virtual void erase(const std::vector<Key>& keys) {
   643       for (int i = 0; i < (int)keys.size(); ++i) {
   644         unlace(keys[i]);
   645       }
   646       Parent::erase(keys);
   647     }
   648 
   649     virtual void clear() {
   650       first.clear();
   651       Parent::clear();
   652     }
   653 
   654   private:
   655     std::vector<_Item> first;
   656   };
   657 
   658   namespace _iterable_maps_bits {
   659     template <typename Item, typename Value>
   660     struct IterableValueMapNode {
   661       IterableValueMapNode(Value _value = Value()) : value(_value) {}
   662       Item prev, next;
   663       Value value;
   664     };
   665   }
   666 
   667   ///\ingroup graph_maps
   668   ///
   669   /// \brief Dynamic iterable map for comparable values.
   670   ///
   671   /// This class provides a special graph map type which can store
   672   /// for each graph item(node, edge, etc.) a value. For each
   673   /// value it is possible to iterate on the keys which mapped to the 
   674   /// given value. The type stores for each value a linked list with
   675   /// the items which mapped to the value, and the values are stored
   676   /// in balanced binary tree. The values of the map can be accessed
   677   /// with stl compatible forward iterator.
   678   ///
   679   /// This type is not reference map so it cannot be modified with
   680   /// the subscription operator.
   681   ///
   682   /// \see InvertableMap
   683   /// 
   684   /// \param _Graph The graph type.
   685   /// \param _Item One of the graph's item type, the key of the map.
   686   /// \param _Value Any comparable value type.
   687   template <typename _Graph, typename _Item, typename _Value>
   688   class IterableValueMap : protected ItemSetTraits<_Graph, _Item> 
   689   ::template Map<_iterable_maps_bits::IterableValueMapNode<_Item, _Value> >
   690   ::Parent {
   691   public:
   692     typedef typename ItemSetTraits<_Graph, _Item> 
   693     ::template Map<_iterable_maps_bits::IterableValueMapNode<_Item, _Value> >
   694     ::Parent Parent;
   695 
   696     /// The key type
   697     typedef _Item Key;
   698     /// The value type
   699     typedef _Value Value;
   700     /// The graph type
   701     typedef _Graph Graph;
   702 
   703     /// \brief Constructor of the Map with a given value.
   704     ///
   705     /// Constructor of the Map with a given value.
   706     explicit IterableValueMap(const Graph& graph, 
   707                               const Value& value = Value()) 
   708       : Parent(graph, _iterable_maps_bits::IterableValueMapNode<_Item, 
   709                _Value>(value)) {
   710       for (typename Parent::ItemIt it(*this); it != INVALID; ++it) {
   711         lace(it);
   712       }
   713     }
   714 
   715   private:
   716     
   717     void unlace(const Key& key) {
   718       typename Parent::Value& node = Parent::operator[](key);
   719       if (node.prev != INVALID) {
   720 	Parent::operator[](node.prev).next = node.next;	
   721       } else {
   722         if (node.next != INVALID) {
   723           first[node.value] = node.next;
   724         } else {
   725           first.erase(node.value);
   726         }
   727       }
   728       if (node.next != INVALID) {
   729 	Parent::operator[](node.next).prev = node.prev;
   730       }
   731     }
   732 
   733     void lace(const Key& key) {
   734       typename Parent::Value& node = Parent::operator[](key);
   735       typename std::map<Value, Key>::iterator it = first.find(node.value);
   736       if (it == first.end()) {
   737         node.prev = node.next = INVALID;
   738         if (node.next != INVALID) {
   739           Parent::operator[](node.next).prev = key;	
   740         }
   741         first.insert(make_pair(node.value, key));
   742       } else {
   743         node.prev = INVALID;
   744         node.next = it->second;
   745         if (node.next != INVALID) {
   746           Parent::operator[](node.next).prev = key;	
   747         }
   748         it->second = key;
   749       }
   750     }
   751 
   752   public:
   753 
   754     /// \brief Forward iterator for values.
   755     ///
   756     /// This iterator is an stl compatible forward
   757     /// iterator on the values of the map. The values can
   758     /// be accessed in the [beginValue, endValue) range.
   759     ///
   760     class ValueIterator 
   761       : public std::iterator<std::forward_iterator_tag, Value> {
   762       friend class IterableValueMap;
   763     private:
   764       ValueIterator(typename std::map<Value, Key>::const_iterator _it) 
   765         : it(_it) {}
   766     public:
   767       
   768       ValueIterator() {}
   769 
   770       ValueIterator& operator++() { ++it; return *this; }
   771       ValueIterator operator++(int) { 
   772         ValueIterator tmp(*this); 
   773         operator++();
   774         return tmp; 
   775       }
   776 
   777       const Value& operator*() const { return it->first; }
   778       const Value* operator->() const { return &(it->first); }
   779 
   780       bool operator==(ValueIterator jt) const { return it == jt.it; }
   781       bool operator!=(ValueIterator jt) const { return it != jt.it; }
   782       
   783     private:
   784       typename std::map<Value, Key>::const_iterator it;
   785     };
   786 
   787     /// \brief Returns an iterator to the first value.
   788     ///
   789     /// Returns an stl compatible iterator to the 
   790     /// first value of the map. The values of the
   791     /// map can be accessed in the [beginValue, endValue)
   792     /// range.
   793     ValueIterator beginValue() const {
   794       return ValueIterator(first.begin());
   795     }
   796 
   797     /// \brief Returns an iterator after the last value.
   798     ///
   799     /// Returns an stl compatible iterator after the 
   800     /// last value of the map. The values of the
   801     /// map can be accessed in the [beginValue, endValue)
   802     /// range.
   803     ValueIterator endValue() const {
   804       return ValueIterator(first.end());
   805     }
   806 
   807     /// \brief Set operation of the map.
   808     ///
   809     /// Set operation of the map.
   810     void set(const Key& key, const Value& value) {
   811       unlace(key);
   812       Parent::operator[](key).value = value;
   813       lace(key);
   814     }
   815 
   816     /// \brief Const subscript operator of the map.
   817     ///
   818     /// Const subscript operator of the map.
   819     const Value& operator[](const Key& key) const {
   820       return Parent::operator[](key).value;
   821     }
   822 
   823     /// \brief Iterator for the keys with the same value.
   824     ///
   825     /// Iterator for the keys with the same value. It works
   826     /// like a graph item iterator in the map, it can be converted
   827     /// the item type of the map, incremented with \c ++ operator, and
   828     /// if the iterator leave the last valid item it will be equal to 
   829     /// \c INVALID.
   830     class ItemIt : public _Item {
   831     public:
   832       typedef _Item Parent;
   833 
   834       /// \brief Invalid constructor \& conversion.
   835       ///
   836       /// This constructor initializes the item to be invalid.
   837       /// \sa Invalid for more details.
   838       ItemIt(Invalid) : Parent(INVALID), _map(0) {}
   839 
   840       /// \brief Creates an iterator with a value.
   841       ///
   842       /// Creates an iterator with a value. It iterates on the 
   843       /// keys which have the given value.
   844       /// \param map The IterableValueMap
   845       /// \param value The value
   846       ItemIt(const IterableValueMap& map, const Value& value) : _map(&map) {
   847         typename std::map<Value, Key>::const_iterator it = 
   848           map.first.find(value); 
   849 	if (it == map.first.end()) {	  
   850 	  Parent::operator=(INVALID);
   851 	} else {
   852 	  Parent::operator=(it->second);
   853 	}
   854       } 
   855 
   856       /// \brief Increment operator.
   857       ///
   858       /// Increment Operator.
   859       ItemIt& operator++() {
   860 	Parent::operator=(_map->IterableValueMap::Parent::
   861 			  operator[](static_cast<Parent&>(*this)).next);
   862 	return *this;
   863       }
   864 
   865 
   866     private:
   867       const IterableValueMap* _map;
   868     };
   869 
   870   protected:
   871     
   872     virtual void erase(const Key& key) {
   873       unlace(key);
   874       Parent::erase(key);
   875     }
   876 
   877     virtual void erase(const std::vector<Key>& keys) {
   878       for (int i = 0; i < (int)keys.size(); ++i) {
   879         unlace(keys[i]);
   880       }
   881       Parent::erase(keys);
   882     }
   883 
   884     virtual void clear() {
   885       first.clear();
   886       Parent::clear();
   887     }
   888 
   889   private:
   890     std::map<Value, Key> first;
   891   };
   892 
   893   /// @}
   894 }