lemon/iterable_maps.h
author deba
Mon, 20 Feb 2006 09:40:07 +0000
changeset 1975 64db671eda28
parent 1953 d4f411003580
child 1990 15fb7a4ea6be
permissions -rw-r--r--
Second renaming of min cut

Minimum => Min
Work => Aux
     1 /* -*- C++ -*-
     2  *
     3  * This file is a part of LEMON, a generic C++ optimization library
     4  *
     5  * Copyright (C) 2003-2006
     6  * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
     7  * (Egervary Research Group on Combinatorial Optimization, EGRES).
     8  *
     9  * Permission to use, modify and distribute this software is granted
    10  * provided that this copyright notice appears in all copies. For
    11  * precise terms see the accompanying LICENSE file.
    12  *
    13  * This software is provided "AS IS" with no warranty of any kind,
    14  * express or implied, and with no claim as to its suitability for any
    15  * purpose.
    16  *
    17  */
    18 
    19 #include <lemon/traits.h>
    20 #include <lemon/invalid.h>
    21 
    22 #include <vector>
    23 #include <map>
    24 
    25 #include <iterator>
    26 #include <limits>
    27 
    28 ///\ingroup maps
    29 ///\file
    30 ///\brief Maps that makes it possible to iterate through the keys having
    31 ///a certain value
    32 ///
    33 ///
    34 
    35 
    36 namespace lemon {
    37 
    38   ///\ingroup graph_maps
    39   ///
    40   /// \brief Dynamic iterable bool map.
    41   ///
    42   /// This class provides a special graph map type which can store
    43   /// for each graph item(node, edge, etc.) a bool value. For both 
    44   /// the true and the false it is possible to iterate on the keys which
    45   /// mapped to the given value.
    46   /// 
    47   /// \param _Graph The graph type.
    48   /// \param _Item One of the graph's item type, the key of the map.
    49   template <typename _Graph, typename _Item>
    50   class IterableBoolMap 
    51     : protected ItemSetTraits<_Graph, _Item>::template Map<int>::Parent {
    52   private:
    53     typedef _Graph Graph;
    54     
    55     typedef typename ItemSetTraits<Graph, _Item>::ItemIt KeyIt;
    56     typedef typename ItemSetTraits<Graph, _Item>
    57     ::template Map<int>::Parent Parent;
    58     
    59     std::vector<_Item> array;
    60     int sep;
    61 
    62     const Graph& graph;
    63 
    64   public:
    65 
    66     /// Indicates that the map if reference map.
    67     typedef True ReferenceMapTag;
    68 
    69     /// The key type
    70     typedef _Item Key;
    71     /// The value type
    72     typedef bool Value;
    73     /// The const reference type.    
    74     typedef const Value& ConstReference;
    75 
    76   private:
    77 
    78     int position(const Key& key) const {
    79       return Parent::operator[](key);
    80     }
    81 
    82   public:
    83 
    84     /// \brief Refernce to the value of the map.
    85     ///
    86     /// This class is near to similar to the bool type. It can
    87     /// be converted to bool and it has the same operators.
    88     class Reference {
    89       friend class IterableBoolMap;
    90     private:
    91       Reference(IterableBoolMap& map, const Key& key) 
    92 	: _key(key), _map(map) {} 
    93     public:
    94 
    95       Reference& operator=(const Reference& value) {
    96 	_map.set(_key, (bool)value);
    97  	return *this;
    98       }
    99 
   100       operator bool() const { 
   101 	return static_cast<const IterableBoolMap&>(_map)[_key]; 
   102       }
   103 
   104       Reference& operator=(bool value) { 
   105 	_map.set(_key, value); 
   106 	return *this; 
   107       }
   108       Reference& operator&=(bool value) {
   109 	_map.set(_key, _map[_key] & value); 
   110 	return *this; 	
   111       }
   112       Reference& operator|=(bool value) {
   113 	_map.set(_key, _map[_key] | value); 
   114 	return *this; 	
   115       }
   116       Reference& operator^=(bool value) {
   117 	_map.set(_key, _map[_key] ^ value); 
   118 	return *this; 	
   119       }
   120     private:
   121       Key _key;
   122       IterableBoolMap& _map; 
   123     };
   124     
   125     /// \brief Constructor of the Map with a default value.
   126     ///
   127     /// Constructor of the Map with a default value.
   128     IterableBoolMap(const Graph& _graph, bool def = false) 
   129       : Parent(_graph), graph(_graph) {
   130       for (KeyIt it(graph); it != INVALID; ++it) {
   131         Parent::set(it, array.size());
   132         array.push_back(it);
   133       }
   134       sep = (def ? array.size() : 0);
   135     }
   136 
   137     /// \brief Const subscript operator of the map.
   138     ///
   139     /// Const subscript operator of the map.
   140     bool operator[](const Key& key) const {
   141       return position(key) < sep;
   142     }
   143 
   144     /// \brief Subscript operator of the map.
   145     ///
   146     /// Subscript operator of the map.
   147     Reference operator[](const Key& key) {
   148       return Reference(*this, key);
   149     }
   150 
   151     /// \brief Set operation of the map.
   152     ///
   153     /// Set operation of the map.
   154     void set(const Key& key, bool value) {
   155       int pos = position(key);
   156       if (value) {
   157         if (pos < sep) return;
   158         Key tmp = array[sep];
   159         array[sep] = key;
   160         Parent::set(key, sep);
   161         array[pos] = tmp;
   162         Parent::set(tmp, pos); 
   163         ++sep;
   164       } else {
   165         if (pos >= sep) return;
   166         --sep;
   167         Key tmp = array[sep];
   168         array[sep] = key;
   169         Parent::set(key, sep);
   170         array[pos] = tmp;
   171         Parent::set(tmp, pos);
   172       }
   173     }
   174 
   175     /// \brief Returns the number of the keys mapped to true.
   176     ///
   177     /// Returns the number of the keys mapped to true.
   178     int trueNum() const {
   179       return sep;
   180     } 
   181     
   182     /// \brief Returns the number of the keys mapped to false.
   183     ///
   184     /// Returns the number of the keys mapped to false.
   185     int falseNum() const {
   186       return array.size() - sep;
   187     }
   188 
   189     /// \brief Iterator for the keys mapped to true.
   190     ///
   191     /// Iterator for the keys mapped to true. It works
   192     /// like a graph item iterator in the map, it can be converted
   193     /// the key type of the map, incremented with \c ++ operator, and
   194     /// if the iterator leave the last valid key it will be equal to 
   195     /// \c INVALID.
   196     class TrueIt : public Key {
   197     public:
   198       typedef Key Parent;
   199       
   200       /// \brief Creates an iterator.
   201       ///
   202       /// Creates an iterator. It iterates on the 
   203       /// keys which mapped to true.
   204       /// \param _map The IterableIntMap
   205       TrueIt(const IterableBoolMap& _map) 
   206         : Parent(_map.sep > 0 ? _map.array[_map.sep - 1] : INVALID), 
   207           map(&_map) {}
   208 
   209       /// \brief Invalid constructor \& conversion.
   210       ///
   211       /// This constructor initializes the key to be invalid.
   212       /// \sa Invalid for more details.
   213       TrueIt(Invalid) : Parent(INVALID), map(0) {}
   214 
   215       /// \brief Increment operator.
   216       ///
   217       /// Increment Operator.
   218       TrueIt& operator++() {
   219         int pos = map->position(*this);
   220         Parent::operator=(pos > 0 ? map->array[pos - 1] : INVALID);
   221         return *this;
   222       }
   223 
   224       
   225     private:
   226       const IterableBoolMap* map;
   227     };
   228 
   229     /// \brief Iterator for the keys mapped to false.
   230     ///
   231     /// Iterator for the keys mapped to false. It works
   232     /// like a graph item iterator in the map, it can be converted
   233     /// the key type of the map, incremented with \c ++ operator, and
   234     /// if the iterator leave the last valid key it will be equal to 
   235     /// \c INVALID.
   236     class FalseIt : public Key {
   237     public:
   238       typedef Key Parent;
   239       
   240       /// \brief Creates an iterator.
   241       ///
   242       /// Creates an iterator. It iterates on the 
   243       /// keys which mapped to false.
   244       /// \param _map The IterableIntMap
   245       FalseIt(const IterableBoolMap& _map) 
   246         : Parent(_map.sep < (int)_map.array.size() ? 
   247                  _map.array.back() : INVALID), map(&_map) {}
   248 
   249       /// \brief Invalid constructor \& conversion.
   250       ///
   251       /// This constructor initializes the key to be invalid.
   252       /// \sa Invalid for more details.
   253       FalseIt(Invalid) : Parent(INVALID), map(0) {}
   254 
   255       /// \brief Increment operator.
   256       ///
   257       /// Increment Operator.
   258       FalseIt& operator++() {
   259         int pos = map->position(*this);
   260         Parent::operator=(pos > map->sep ? map->array[pos - 1] : INVALID);
   261         return *this;
   262       }
   263 
   264     private:
   265       const IterableBoolMap* map;
   266     };
   267 
   268     /// \brief Iterator for the keys mapped to a given value.
   269     ///
   270     /// Iterator for the keys mapped to a given value. It works
   271     /// like a graph item iterator in the map, it can be converted
   272     /// the key type of the map, incremented with \c ++ operator, and
   273     /// if the iterator leave the last valid key it will be equal to 
   274     /// \c INVALID.
   275     class ItemIt : public Key {
   276     public:
   277       typedef Key Parent;
   278       
   279       /// \brief Creates an iterator.
   280       ///
   281       /// Creates an iterator. It iterates on the 
   282       /// keys which mapped to false.
   283       /// \param _map The IterableIntMap
   284       /// \param value Which elements should be iterated.
   285       ItemIt(const IterableBoolMap& _map, bool value) 
   286         : Parent(value ? (_map.sep > 0 ? _map.array[_map.sep - 1] : INVALID) :
   287                  (_map.sep < (int)_map.array.size() ? 
   288                   _map.array.back() : INVALID)), map(&_map) {}
   289 
   290       /// \brief Invalid constructor \& conversion.
   291       ///
   292       /// This constructor initializes the key to be invalid.
   293       /// \sa Invalid for more details.
   294       ItemIt(Invalid) : Parent(INVALID), map(0) {}
   295 
   296       /// \brief Increment operator.
   297       ///
   298       /// Increment Operator.
   299       ItemIt& operator++() {
   300         int pos = map->position(*this);
   301         int sep = pos >= map->sep ? map->sep : 0;
   302         Parent::operator=(pos > sep ? map->array[pos - 1] : INVALID);
   303         return *this;
   304       }
   305 
   306     private:
   307       const IterableBoolMap* map;
   308     };
   309 
   310   protected:
   311     
   312     virtual void add(const Key& key) {
   313       Parent::add(key);
   314       Parent::set(key, array.size());
   315       array.push_back(key);
   316     }
   317 
   318     virtual void add(const std::vector<Key>& keys) {
   319       Parent::add(keys);
   320       for (int i = 0; i < (int)keys.size(); ++i) {
   321         Parent::set(keys[i], array.size());
   322         array.push_back(keys[i]);
   323       }
   324     }
   325 
   326     virtual void erase(const Key& key) {
   327       int pos = position(key); 
   328       if (pos < sep) {
   329         --sep;
   330         Parent::set(array[sep], pos);
   331         array[pos] = array[sep];
   332         Parent::set(array.back(), sep);
   333         array[sep] = array.back();
   334         array.pop_back();
   335       } else {
   336         Parent::set(array.back(), pos);
   337         array[pos] = array.back();
   338         array.pop_back();
   339       }
   340       Parent::erase(key);
   341     }
   342 
   343     virtual void erase(const std::vector<Key>& keys) {
   344       for (int i = 0; i < (int)keys.size(); ++i) {
   345         int pos = position(keys[i]); 
   346         if (pos < sep) {
   347           --sep;
   348           Parent::set(array[sep], pos);
   349           array[pos] = array[sep];
   350           Parent::set(array.back(), sep);
   351           array[sep] = array.back();
   352           array.pop_back();
   353         } else {
   354           Parent::set(array.back(), pos);
   355           array[pos] = array.back();
   356           array.pop_back();
   357         }
   358       }
   359       Parent::erase(keys);
   360     }    
   361 
   362     virtual void build() {
   363       Parent::build();
   364       for (KeyIt it(graph); it != INVALID; ++it) {
   365         Parent::set(it, array.size());
   366         array.push_back(it);
   367       }
   368       sep = 0;      
   369     }
   370 
   371     virtual void clear() {
   372       array.clear();
   373       sep = 0;
   374       Parent::clear();
   375     }
   376     
   377   };
   378   
   379 
   380   namespace _iterable_maps_bits {
   381     template <typename Item>
   382     struct IterableIntMapNode {
   383       IterableIntMapNode() : value(-1) {}
   384       IterableIntMapNode(int _value) : value(_value) {}
   385       Item prev, next;
   386       int value;
   387     };
   388   }
   389 
   390   ///\ingroup graph_maps
   391   ///
   392   /// \brief Dynamic iterable integer map.
   393   ///
   394   /// This class provides a special graph map type which can store
   395   /// for each graph item(node, edge, etc.) an integer value. For each
   396   /// non negative value it is possible to iterate on the keys which
   397   /// mapped to the given value.
   398   /// 
   399   /// \param _Graph The graph type.
   400   /// \param _Item One of the graph's item type, the key of the map.
   401   template <typename _Graph, typename _Item>
   402   class IterableIntMap : protected ItemSetTraits<_Graph, _Item> 
   403   ::template Map<_iterable_maps_bits::IterableIntMapNode<_Item> >::Parent {
   404   public:
   405     typedef typename ItemSetTraits<_Graph, _Item> 
   406     ::template Map<_iterable_maps_bits::IterableIntMapNode<_Item> >
   407     ::Parent Parent;
   408 
   409     /// The key type
   410     typedef _Item Key;
   411     /// The value type
   412     typedef int Value;
   413     /// The graph type
   414     typedef _Graph Graph;
   415 
   416     /// \brief Constructor of the Map.
   417     ///
   418     /// Constructor of the Map. It set all values -1.
   419     explicit IterableIntMap(const Graph& graph) 
   420       : Parent(graph) {}
   421 
   422     /// \brief Constructor of the Map with a given value.
   423     ///
   424     /// Constructor of the Map with a given value.
   425     explicit IterableIntMap(const Graph& graph, int value) 
   426       : Parent(graph, _iterable_maps_bits::IterableIntMapNode<_Item>(value)) {
   427       if (value >= 0) {
   428 	for (typename Parent::ItemIt it(*this); it != INVALID; ++it) {
   429 	  lace(it);
   430 	}
   431       }
   432     }
   433 
   434   private:
   435     
   436     void unlace(const Key& key) {
   437       typename Parent::Value& node = Parent::operator[](key);
   438       if (node.value < 0) return;
   439       if (node.prev != INVALID) {
   440 	Parent::operator[](node.prev).next = node.next;	
   441       } else {
   442 	first[node.value] = node.next;
   443       }
   444       if (node.next != INVALID) {
   445 	Parent::operator[](node.next).prev = node.prev;
   446       }
   447       while (!first.empty() && first.back() == INVALID) {
   448 	first.pop_back();
   449       }
   450     }
   451 
   452     void lace(const Key& key) {
   453       typename Parent::Value& node = Parent::operator[](key);
   454       if (node.value < 0) return;
   455       if (node.value >= (int)first.size()) {
   456 	first.resize(node.value + 1, INVALID);
   457       } 
   458       node.prev = INVALID;
   459       node.next = first[node.value];
   460       if (node.next != INVALID) {
   461 	Parent::operator[](node.next).prev = key;	
   462       }
   463       first[node.value] = key;
   464     }
   465 
   466   public:
   467 
   468     /// Indicates that the map if reference map.
   469     typedef True ReferenceMapTag;
   470 
   471     /// \brief Refernce to the value of the map.
   472     ///
   473     /// This class is near to similar to the int type. It can
   474     /// be converted to int and it has the same operators.
   475     class Reference {
   476       friend class IterableIntMap;
   477     private:
   478       Reference(IterableIntMap& map, const Key& key) 
   479 	: _key(key), _map(map) {} 
   480     public:
   481 
   482       Reference& operator=(const Reference& value) {
   483 	_map.set(_key, (const int&)value);
   484  	return *this;
   485       }
   486 
   487       operator const int&() const { 
   488 	return static_cast<const IterableIntMap&>(_map)[_key]; 
   489       }
   490 
   491       Reference& operator=(int value) { 
   492 	_map.set(_key, value); 
   493 	return *this; 
   494       }
   495       Reference& operator++() {
   496 	_map.set(_key, _map[_key] + 1); 
   497 	return *this; 	
   498       }
   499       int operator++(int) {
   500 	int value = _map[_key];
   501 	_map.set(_key, value + 1); 
   502 	return value; 	
   503       }
   504       Reference& operator--() {
   505 	_map.set(_key, _map[_key] - 1); 
   506 	return *this; 	
   507       }
   508       int operator--(int) {
   509 	int value = _map[_key];
   510 	_map.set(_key, value - 1); 
   511 	return value; 	
   512       }
   513       Reference& operator+=(int value) { 
   514 	_map.set(_key, _map[_key] + value); 
   515 	return *this;
   516       }
   517       Reference& operator-=(int value) { 
   518 	_map.set(_key, _map[_key] - value); 
   519 	return *this;
   520       }
   521       Reference& operator*=(int value) { 
   522 	_map.set(_key, _map[_key] * value); 
   523 	return *this;
   524       }
   525       Reference& operator/=(int value) { 
   526 	_map.set(_key, _map[_key] / value); 
   527 	return *this;
   528       }
   529       Reference& operator%=(int value) { 
   530 	_map.set(_key, _map[_key] % value); 
   531 	return *this;
   532       }
   533       Reference& operator&=(int value) { 
   534 	_map.set(_key, _map[_key] & value); 
   535 	return *this;
   536       }
   537       Reference& operator|=(int value) { 
   538 	_map.set(_key, _map[_key] | value); 
   539 	return *this;
   540       }
   541       Reference& operator^=(int value) { 
   542 	_map.set(_key, _map[_key] ^ value); 
   543 	return *this;
   544       }
   545       Reference& operator<<=(int value) { 
   546 	_map.set(_key, _map[_key] << value); 
   547 	return *this;
   548       }
   549       Reference& operator>>=(int value) { 
   550 	_map.set(_key, _map[_key] >> value); 
   551 	return *this;
   552       }
   553 
   554     private:
   555       Key _key;
   556       IterableIntMap& _map; 
   557     };
   558 
   559     /// The const reference type.    
   560     typedef const Value& ConstReference;
   561 
   562     /// \brief Gives back the maximal value plus one.
   563     ///
   564     /// Gives back the maximal value plus one.
   565     unsigned int size() const {
   566       return first.size();
   567     }
   568     
   569     /// \brief Set operation of the map.
   570     ///
   571     /// Set operation of the map.
   572     void set(const Key& key, const Value& value) {
   573       unlace(key);
   574       Parent::operator[](key).value = value;
   575       lace(key);
   576     }
   577 
   578     /// \brief Const subscript operator of the map.
   579     ///
   580     /// Const subscript operator of the map.
   581     const Value& operator[](const Key& key) const {
   582       return Parent::operator[](key).value;
   583     }
   584 
   585     /// \brief Subscript operator of the map.
   586     ///
   587     /// Subscript operator of the map.
   588     Reference operator[](const Key& key) {
   589       return Reference(*this, key);
   590     }
   591 
   592     /// \brief Iterator for the keys with the same value.
   593     ///
   594     /// Iterator for the keys with the same value. It works
   595     /// like a graph item iterator in the map, it can be converted
   596     /// the item type of the map, incremented with \c ++ operator, and
   597     /// if the iterator leave the last valid item it will be equal to 
   598     /// \c INVALID.
   599     class ItemIt : public _Item {
   600     public:
   601       typedef _Item Parent;
   602 
   603       /// \brief Invalid constructor \& conversion.
   604       ///
   605       /// This constructor initializes the item to be invalid.
   606       /// \sa Invalid for more details.
   607       ItemIt(Invalid) : Parent(INVALID), _map(0) {}
   608 
   609       /// \brief Creates an iterator with a value.
   610       ///
   611       /// Creates an iterator with a value. It iterates on the 
   612       /// keys which have the given value.
   613       /// \param map The IterableIntMap
   614       /// \param value The value
   615       ItemIt(const IterableIntMap& map, int value) : _map(&map) {
   616 	if (value < 0 || value >= (int)_map->first.size()) {	  
   617 	  Parent::operator=(INVALID);
   618 	} else {
   619 	  Parent::operator=(_map->first[value]);
   620 	}
   621       } 
   622 
   623       /// \brief Increment operator.
   624       ///
   625       /// Increment Operator.
   626       ItemIt& operator++() {
   627 	Parent::operator=(_map->IterableIntMap::Parent::
   628 			  operator[](static_cast<Parent&>(*this)).next);
   629 	return *this;
   630       }
   631 
   632 
   633     private:
   634       const IterableIntMap* _map;
   635     };
   636 
   637   protected:
   638     
   639     virtual void erase(const Key& key) {
   640       unlace(key);
   641       Parent::erase(key);
   642     }
   643 
   644     virtual void erase(const std::vector<Key>& keys) {
   645       for (int i = 0; i < (int)keys.size(); ++i) {
   646         unlace(keys[i]);
   647       }
   648       Parent::erase(keys);
   649     }
   650 
   651     virtual void clear() {
   652       first.clear();
   653       Parent::clear();
   654     }
   655 
   656   private:
   657     std::vector<_Item> first;
   658   };
   659 
   660   namespace _iterable_maps_bits {
   661     template <typename Item, typename Value>
   662     struct IterableValueMapNode {
   663       IterableValueMapNode(Value _value = Value()) : value(_value) {}
   664       Item prev, next;
   665       Value value;
   666     };
   667   }
   668 
   669   ///\ingroup graph_maps
   670   ///
   671   /// \brief Dynamic iterable map for comparable values.
   672   ///
   673   /// This class provides a special graph map type which can store
   674   /// for each graph item(node, edge, etc.) a value. For each
   675   /// value it is possible to iterate on the keys which mapped to the 
   676   /// given value. The type stores for each value a linked list with
   677   /// the items which mapped to the value, and the values are stored
   678   /// in balanced binary tree. The values of the map can be accessed
   679   /// with stl compatible forward iterator.
   680   ///
   681   /// This type is not reference map so it cannot be modified with
   682   /// the subscription operator.
   683   ///
   684   /// \see InvertableMap
   685   /// 
   686   /// \param _Graph The graph type.
   687   /// \param _Item One of the graph's item type, the key of the map.
   688   /// \param _Value Any comparable value type.
   689   template <typename _Graph, typename _Item, typename _Value>
   690   class IterableValueMap : protected ItemSetTraits<_Graph, _Item> 
   691   ::template Map<_iterable_maps_bits::IterableValueMapNode<_Item, _Value> >
   692   ::Parent {
   693   public:
   694     typedef typename ItemSetTraits<_Graph, _Item> 
   695     ::template Map<_iterable_maps_bits::IterableValueMapNode<_Item, _Value> >
   696     ::Parent Parent;
   697 
   698     /// The key type
   699     typedef _Item Key;
   700     /// The value type
   701     typedef _Value Value;
   702     /// The graph type
   703     typedef _Graph Graph;
   704 
   705     /// \brief Constructor of the Map with a given value.
   706     ///
   707     /// Constructor of the Map with a given value.
   708     explicit IterableValueMap(const Graph& graph, 
   709                               const Value& value = Value()) 
   710       : Parent(graph, _iterable_maps_bits::IterableValueMapNode<_Item, 
   711                _Value>(value)) {
   712       for (typename Parent::ItemIt it(*this); it != INVALID; ++it) {
   713         lace(it);
   714       }
   715     }
   716 
   717   private:
   718     
   719     void unlace(const Key& key) {
   720       typename Parent::Value& node = Parent::operator[](key);
   721       if (node.prev != INVALID) {
   722 	Parent::operator[](node.prev).next = node.next;	
   723       } else {
   724         if (node.next != INVALID) {
   725           first[node.value] = node.next;
   726         } else {
   727           first.erase(node.value);
   728         }
   729       }
   730       if (node.next != INVALID) {
   731 	Parent::operator[](node.next).prev = node.prev;
   732       }
   733     }
   734 
   735     void lace(const Key& key) {
   736       typename Parent::Value& node = Parent::operator[](key);
   737       typename std::map<Value, Key>::iterator it = first.find(node.value);
   738       if (it == first.end()) {
   739         node.prev = node.next = INVALID;
   740         if (node.next != INVALID) {
   741           Parent::operator[](node.next).prev = key;	
   742         }
   743         first.insert(make_pair(node.value, key));
   744       } else {
   745         node.prev = INVALID;
   746         node.next = it->second;
   747         if (node.next != INVALID) {
   748           Parent::operator[](node.next).prev = key;	
   749         }
   750         it->second = key;
   751       }
   752     }
   753 
   754   public:
   755 
   756     /// \brief Forward iterator for values.
   757     ///
   758     /// This iterator is an stl compatible forward
   759     /// iterator on the values of the map. The values can
   760     /// be accessed in the [beginValue, endValue) range.
   761     ///
   762     class ValueIterator 
   763       : public std::iterator<std::forward_iterator_tag, Value> {
   764       friend class IterableValueMap;
   765     private:
   766       ValueIterator(typename std::map<Value, Key>::const_iterator _it) 
   767         : it(_it) {}
   768     public:
   769       
   770       ValueIterator() {}
   771 
   772       ValueIterator& operator++() { ++it; return *this; }
   773       ValueIterator operator++(int) { 
   774         ValueIterator tmp(*this); 
   775         operator++();
   776         return tmp; 
   777       }
   778 
   779       const Value& operator*() const { return it->first; }
   780       const Value* operator->() const { return &(it->first); }
   781 
   782       bool operator==(ValueIterator jt) const { return it == jt.it; }
   783       bool operator!=(ValueIterator jt) const { return it != jt.it; }
   784       
   785     private:
   786       typename std::map<Value, Key>::const_iterator it;
   787     };
   788 
   789     /// \brief Returns an iterator to the first value.
   790     ///
   791     /// Returns an stl compatible iterator to the 
   792     /// first value of the map. The values of the
   793     /// map can be accessed in the [beginValue, endValue)
   794     /// range.
   795     ValueIterator beginValue() const {
   796       return ValueIterator(first.begin());
   797     }
   798 
   799     /// \brief Returns an iterator after the last value.
   800     ///
   801     /// Returns an stl compatible iterator after the 
   802     /// last value of the map. The values of the
   803     /// map can be accessed in the [beginValue, endValue)
   804     /// range.
   805     ValueIterator endValue() const {
   806       return ValueIterator(first.end());
   807     }
   808 
   809     /// \brief Set operation of the map.
   810     ///
   811     /// Set operation of the map.
   812     void set(const Key& key, const Value& value) {
   813       unlace(key);
   814       Parent::operator[](key).value = value;
   815       lace(key);
   816     }
   817 
   818     /// \brief Const subscript operator of the map.
   819     ///
   820     /// Const subscript operator of the map.
   821     const Value& operator[](const Key& key) const {
   822       return Parent::operator[](key).value;
   823     }
   824 
   825     /// \brief Iterator for the keys with the same value.
   826     ///
   827     /// Iterator for the keys with the same value. It works
   828     /// like a graph item iterator in the map, it can be converted
   829     /// the item type of the map, incremented with \c ++ operator, and
   830     /// if the iterator leave the last valid item it will be equal to 
   831     /// \c INVALID.
   832     class ItemIt : public _Item {
   833     public:
   834       typedef _Item Parent;
   835 
   836       /// \brief Invalid constructor \& conversion.
   837       ///
   838       /// This constructor initializes the item to be invalid.
   839       /// \sa Invalid for more details.
   840       ItemIt(Invalid) : Parent(INVALID), _map(0) {}
   841 
   842       /// \brief Creates an iterator with a value.
   843       ///
   844       /// Creates an iterator with a value. It iterates on the 
   845       /// keys which have the given value.
   846       /// \param map The IterableValueMap
   847       /// \param value The value
   848       ItemIt(const IterableValueMap& map, const Value& value) : _map(&map) {
   849         typename std::map<Value, Key>::const_iterator it = 
   850           map.first.find(value); 
   851 	if (it == map.first.end()) {	  
   852 	  Parent::operator=(INVALID);
   853 	} else {
   854 	  Parent::operator=(it->second);
   855 	}
   856       } 
   857 
   858       /// \brief Increment operator.
   859       ///
   860       /// Increment Operator.
   861       ItemIt& operator++() {
   862 	Parent::operator=(_map->IterableValueMap::Parent::
   863 			  operator[](static_cast<Parent&>(*this)).next);
   864 	return *this;
   865       }
   866 
   867 
   868     private:
   869       const IterableValueMap* _map;
   870     };
   871 
   872   protected:
   873     
   874     virtual void erase(const Key& key) {
   875       unlace(key);
   876       Parent::erase(key);
   877     }
   878 
   879     virtual void erase(const std::vector<Key>& keys) {
   880       for (int i = 0; i < (int)keys.size(); ++i) {
   881         unlace(keys[i]);
   882       }
   883       Parent::erase(keys);
   884     }
   885 
   886     virtual void clear() {
   887       first.clear();
   888       Parent::clear();
   889     }
   890 
   891   private:
   892     std::map<Value, Key> first;
   893   };
   894 
   895   /// @}
   896 }