lemon/iterable_maps.h
author alpar
Tue, 11 Jul 2006 13:51:52 +0000
changeset 2123 85c6f5e82108
parent 2031 080d51024ac5
child 2210 25aab9493dd2
permissions -rw-r--r--
Minor doc improvements
     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/bits/traits.h>
    20 #include <lemon/bits/invalid.h>
    21 
    22 #include <lemon/bits/default_map.h>
    23 #include <lemon/bits/map_extender.h>
    24 
    25 #include <vector>
    26 #include <map>
    27 
    28 #include <iterator>
    29 #include <limits>
    30 
    31 ///\ingroup maps
    32 ///\file
    33 ///\brief Maps that makes it possible to iterate through the keys having
    34 ///a certain value
    35 ///
    36 ///
    37 
    38 
    39 namespace lemon {
    40 
    41   ///\ingroup graph_maps
    42   ///
    43   /// \brief Dynamic iterable bool map.
    44   ///
    45   /// This class provides a special graph map type which can store
    46   /// for each graph item(node, edge, etc.) a bool value. For both 
    47   /// the true and the false it is possible to iterate on the keys which
    48   /// mapped to the given value.
    49   /// 
    50   /// \param _Graph The graph type.
    51   /// \param _Item One of the graph's item type, the key of the map.
    52   template <typename _Graph, typename _Item>
    53   class IterableBoolMap : protected DefaultMap<_Graph, _Item, int> {
    54   private:
    55     typedef _Graph Graph;
    56     
    57     typedef typename ItemSetTraits<Graph, _Item>::ItemIt KeyIt;
    58     typedef DefaultMap<_Graph, _Item, int> Parent;
    59     
    60     std::vector<_Item> array;
    61     int sep;
    62 
    63     const Graph& graph;
    64 
    65   public:
    66 
    67     /// Indicates that the map if reference map.
    68     typedef True ReferenceMapTag;
    69 
    70     /// The key type
    71     typedef _Item Key;
    72     /// The value type
    73     typedef bool Value;
    74     /// The const reference type.    
    75     typedef const Value& ConstReference;
    76 
    77   private:
    78 
    79     int position(const Key& key) const {
    80       return Parent::operator[](key);
    81     }
    82 
    83   public:
    84 
    85     /// \brief Refernce to the value of the map.
    86     ///
    87     /// This class is near to similar to the bool type. It can
    88     /// be converted to bool and it has the same operators.
    89     class Reference {
    90       friend class IterableBoolMap;
    91     private:
    92       Reference(IterableBoolMap& map, const Key& key) 
    93 	: _key(key), _map(map) {} 
    94     public:
    95 
    96       Reference& operator=(const Reference& value) {
    97 	_map.set(_key, (bool)value);
    98  	return *this;
    99       }
   100 
   101       operator bool() const { 
   102 	return static_cast<const IterableBoolMap&>(_map)[_key]; 
   103       }
   104 
   105       Reference& operator=(bool value) { 
   106 	_map.set(_key, value); 
   107 	return *this; 
   108       }
   109       Reference& operator&=(bool value) {
   110 	_map.set(_key, _map[_key] & value); 
   111 	return *this; 	
   112       }
   113       Reference& operator|=(bool value) {
   114 	_map.set(_key, _map[_key] | value); 
   115 	return *this; 	
   116       }
   117       Reference& operator^=(bool value) {
   118 	_map.set(_key, _map[_key] ^ value); 
   119 	return *this; 	
   120       }
   121     private:
   122       Key _key;
   123       IterableBoolMap& _map; 
   124     };
   125     
   126     /// \brief Constructor of the Map with a default value.
   127     ///
   128     /// Constructor of the Map with a default value.
   129     explicit IterableBoolMap(const Graph& _graph, bool def = false) 
   130       : Parent(_graph), graph(_graph) {
   131       for (KeyIt it(graph); it != INVALID; ++it) {
   132         Parent::set(it, array.size());
   133         array.push_back(it);
   134       }
   135       sep = (def ? array.size() : 0);
   136     }
   137 
   138     /// \brief Const subscript operator of the map.
   139     ///
   140     /// Const subscript operator of the map.
   141     bool operator[](const Key& key) const {
   142       return position(key) < sep;
   143     }
   144 
   145     /// \brief Subscript operator of the map.
   146     ///
   147     /// Subscript operator of the map.
   148     Reference operator[](const Key& key) {
   149       return Reference(*this, key);
   150     }
   151 
   152     /// \brief Set operation of the map.
   153     ///
   154     /// Set operation of the map.
   155     void set(const Key& key, bool value) {
   156       int pos = position(key);
   157       if (value) {
   158         if (pos < sep) return;
   159         Key tmp = array[sep];
   160         array[sep] = key;
   161         Parent::set(key, sep);
   162         array[pos] = tmp;
   163         Parent::set(tmp, pos); 
   164         ++sep;
   165       } else {
   166         if (pos >= sep) return;
   167         --sep;
   168         Key tmp = array[sep];
   169         array[sep] = key;
   170         Parent::set(key, sep);
   171         array[pos] = tmp;
   172         Parent::set(tmp, pos);
   173       }
   174     }
   175 
   176     /// \brief Returns the number of the keys mapped to true.
   177     ///
   178     /// Returns the number of the keys mapped to true.
   179     int trueNum() const {
   180       return sep;
   181     } 
   182     
   183     /// \brief Returns the number of the keys mapped to false.
   184     ///
   185     /// Returns the number of the keys mapped to false.
   186     int falseNum() const {
   187       return array.size() - sep;
   188     }
   189 
   190     /// \brief Iterator for the keys mapped to true.
   191     ///
   192     /// Iterator for the keys mapped to true. It works
   193     /// like a graph item iterator in the map, it can be converted
   194     /// the key type of the map, incremented with \c ++ operator, and
   195     /// if the iterator leave the last valid key it will be equal to 
   196     /// \c INVALID.
   197     class TrueIt : public Key {
   198     public:
   199       typedef Key Parent;
   200       
   201       /// \brief Creates an iterator.
   202       ///
   203       /// Creates an iterator. It iterates on the 
   204       /// keys which mapped to true.
   205       /// \param _map The IterableIntMap
   206       explicit TrueIt(const IterableBoolMap& _map) 
   207         : Parent(_map.sep > 0 ? _map.array[_map.sep - 1] : INVALID), 
   208           map(&_map) {}
   209 
   210       /// \brief Invalid constructor \& conversion.
   211       ///
   212       /// This constructor initializes the key to be invalid.
   213       /// \sa Invalid for more details.
   214       TrueIt(Invalid) : Parent(INVALID), map(0) {}
   215 
   216       /// \brief Increment operator.
   217       ///
   218       /// Increment Operator.
   219       TrueIt& operator++() {
   220         int pos = map->position(*this);
   221         Parent::operator=(pos > 0 ? map->array[pos - 1] : INVALID);
   222         return *this;
   223       }
   224 
   225       
   226     private:
   227       const IterableBoolMap* map;
   228     };
   229 
   230     /// \brief Iterator for the keys mapped to false.
   231     ///
   232     /// Iterator for the keys mapped to false. It works
   233     /// like a graph item iterator in the map, it can be converted
   234     /// the key type of the map, incremented with \c ++ operator, and
   235     /// if the iterator leave the last valid key it will be equal to 
   236     /// \c INVALID.
   237     class FalseIt : public Key {
   238     public:
   239       typedef Key Parent;
   240       
   241       /// \brief Creates an iterator.
   242       ///
   243       /// Creates an iterator. It iterates on the 
   244       /// keys which mapped to false.
   245       /// \param _map The IterableIntMap
   246       explicit FalseIt(const IterableBoolMap& _map) 
   247         : Parent(_map.sep < (int)_map.array.size() ? 
   248                  _map.array.back() : INVALID), map(&_map) {}
   249 
   250       /// \brief Invalid constructor \& conversion.
   251       ///
   252       /// This constructor initializes the key to be invalid.
   253       /// \sa Invalid for more details.
   254       FalseIt(Invalid) : Parent(INVALID), map(0) {}
   255 
   256       /// \brief Increment operator.
   257       ///
   258       /// Increment Operator.
   259       FalseIt& operator++() {
   260         int pos = map->position(*this);
   261         Parent::operator=(pos > map->sep ? map->array[pos - 1] : INVALID);
   262         return *this;
   263       }
   264 
   265     private:
   266       const IterableBoolMap* map;
   267     };
   268 
   269     /// \brief Iterator for the keys mapped to a given value.
   270     ///
   271     /// Iterator for the keys mapped to a given value. It works
   272     /// like a graph item iterator in the map, it can be converted
   273     /// the key type of the map, incremented with \c ++ operator, and
   274     /// if the iterator leave the last valid key it will be equal to 
   275     /// \c INVALID.
   276     class ItemIt : public Key {
   277     public:
   278       typedef Key Parent;
   279       
   280       /// \brief Creates an iterator.
   281       ///
   282       /// Creates an iterator. It iterates on the 
   283       /// keys which mapped to false.
   284       /// \param _map The IterableIntMap
   285       /// \param value Which elements should be iterated.
   286       ItemIt(const IterableBoolMap& _map, bool value) 
   287         : Parent(value ? (_map.sep > 0 ? _map.array[_map.sep - 1] : INVALID) :
   288                  (_map.sep < (int)_map.array.size() ? 
   289                   _map.array.back() : INVALID)), map(&_map) {}
   290 
   291       /// \brief Invalid constructor \& conversion.
   292       ///
   293       /// This constructor initializes the key to be invalid.
   294       /// \sa Invalid for more details.
   295       ItemIt(Invalid) : Parent(INVALID), map(0) {}
   296 
   297       /// \brief Increment operator.
   298       ///
   299       /// Increment Operator.
   300       ItemIt& operator++() {
   301         int pos = map->position(*this);
   302         int sep = pos >= map->sep ? map->sep : 0;
   303         Parent::operator=(pos > sep ? map->array[pos - 1] : INVALID);
   304         return *this;
   305       }
   306 
   307     private:
   308       const IterableBoolMap* map;
   309     };
   310 
   311   protected:
   312     
   313     virtual void add(const Key& key) {
   314       Parent::add(key);
   315       Parent::set(key, array.size());
   316       array.push_back(key);
   317     }
   318 
   319     virtual void add(const std::vector<Key>& keys) {
   320       Parent::add(keys);
   321       for (int i = 0; i < (int)keys.size(); ++i) {
   322         Parent::set(keys[i], array.size());
   323         array.push_back(keys[i]);
   324       }
   325     }
   326 
   327     virtual void erase(const Key& key) {
   328       int pos = position(key); 
   329       if (pos < sep) {
   330         --sep;
   331         Parent::set(array[sep], pos);
   332         array[pos] = array[sep];
   333         Parent::set(array.back(), sep);
   334         array[sep] = array.back();
   335         array.pop_back();
   336       } else {
   337         Parent::set(array.back(), pos);
   338         array[pos] = array.back();
   339         array.pop_back();
   340       }
   341       Parent::erase(key);
   342     }
   343 
   344     virtual void erase(const std::vector<Key>& keys) {
   345       for (int i = 0; i < (int)keys.size(); ++i) {
   346         int pos = position(keys[i]); 
   347         if (pos < sep) {
   348           --sep;
   349           Parent::set(array[sep], pos);
   350           array[pos] = array[sep];
   351           Parent::set(array.back(), sep);
   352           array[sep] = array.back();
   353           array.pop_back();
   354         } else {
   355           Parent::set(array.back(), pos);
   356           array[pos] = array.back();
   357           array.pop_back();
   358         }
   359       }
   360       Parent::erase(keys);
   361     }    
   362 
   363     virtual void build() {
   364       Parent::build();
   365       for (KeyIt it(graph); it != INVALID; ++it) {
   366         Parent::set(it, array.size());
   367         array.push_back(it);
   368       }
   369       sep = 0;      
   370     }
   371 
   372     virtual void clear() {
   373       array.clear();
   374       sep = 0;
   375       Parent::clear();
   376     }
   377     
   378   };
   379   
   380 
   381   namespace _iterable_maps_bits {
   382     template <typename Item>
   383     struct IterableIntMapNode {
   384       IterableIntMapNode() : value(-1) {}
   385       IterableIntMapNode(int _value) : value(_value) {}
   386       Item prev, next;
   387       int value;
   388     };
   389   }
   390 
   391   ///\ingroup graph_maps
   392   ///
   393   /// \brief Dynamic iterable integer map.
   394   ///
   395   /// This class provides a special graph map type which can store
   396   /// for each graph item(node, edge, etc.) an integer value. For each
   397   /// non negative value it is possible to iterate on the keys which
   398   /// mapped to the given value.
   399   /// 
   400   /// \param _Graph The graph type.
   401   /// \param _Item One of the graph's item type, the key of the map.
   402   template <typename _Graph, typename _Item>
   403   class IterableIntMap 
   404     : protected MapExtender<DefaultMap<_Graph, _Item, _iterable_maps_bits::
   405                                        IterableIntMapNode<_Item> > >{
   406   public:
   407     typedef MapExtender<DefaultMap<_Graph, _Item, _iterable_maps_bits::
   408                                    IterableIntMapNode<_Item> > > Parent;
   409 
   410     /// The key type
   411     typedef _Item Key;
   412     /// The value type
   413     typedef int Value;
   414     /// The graph type
   415     typedef _Graph Graph;
   416 
   417     /// \brief Constructor of the Map.
   418     ///
   419     /// Constructor of the Map. It set all values -1.
   420     explicit IterableIntMap(const Graph& graph) 
   421       : Parent(graph) {}
   422 
   423     /// \brief Constructor of the Map with a given value.
   424     ///
   425     /// Constructor of the Map with a given value.
   426     explicit IterableIntMap(const Graph& graph, int value) 
   427       : Parent(graph, _iterable_maps_bits::IterableIntMapNode<_Item>(value)) {
   428       if (value >= 0) {
   429 	for (typename Parent::ItemIt it(*this); it != INVALID; ++it) {
   430 	  lace(it);
   431 	}
   432       }
   433     }
   434 
   435   private:
   436     
   437     void unlace(const Key& key) {
   438       typename Parent::Value& node = Parent::operator[](key);
   439       if (node.value < 0) return;
   440       if (node.prev != INVALID) {
   441 	Parent::operator[](node.prev).next = node.next;	
   442       } else {
   443 	first[node.value] = node.next;
   444       }
   445       if (node.next != INVALID) {
   446 	Parent::operator[](node.next).prev = node.prev;
   447       }
   448       while (!first.empty() && first.back() == INVALID) {
   449 	first.pop_back();
   450       }
   451     }
   452 
   453     void lace(const Key& key) {
   454       typename Parent::Value& node = Parent::operator[](key);
   455       if (node.value < 0) return;
   456       if (node.value >= (int)first.size()) {
   457 	first.resize(node.value + 1, INVALID);
   458       } 
   459       node.prev = INVALID;
   460       node.next = first[node.value];
   461       if (node.next != INVALID) {
   462 	Parent::operator[](node.next).prev = key;	
   463       }
   464       first[node.value] = key;
   465     }
   466 
   467   public:
   468 
   469     /// Indicates that the map if reference map.
   470     typedef True ReferenceMapTag;
   471 
   472     /// \brief Refernce to the value of the map.
   473     ///
   474     /// This class is near to similar to the int type. It can
   475     /// be converted to int and it has the same operators.
   476     class Reference {
   477       friend class IterableIntMap;
   478     private:
   479       Reference(IterableIntMap& map, const Key& key) 
   480 	: _key(key), _map(map) {} 
   481     public:
   482 
   483       Reference& operator=(const Reference& value) {
   484 	_map.set(_key, (const int&)value);
   485  	return *this;
   486       }
   487 
   488       operator const int&() const { 
   489 	return static_cast<const IterableIntMap&>(_map)[_key]; 
   490       }
   491 
   492       Reference& operator=(int value) { 
   493 	_map.set(_key, value); 
   494 	return *this; 
   495       }
   496       Reference& operator++() {
   497 	_map.set(_key, _map[_key] + 1); 
   498 	return *this; 	
   499       }
   500       int operator++(int) {
   501 	int value = _map[_key];
   502 	_map.set(_key, value + 1); 
   503 	return value; 	
   504       }
   505       Reference& operator--() {
   506 	_map.set(_key, _map[_key] - 1); 
   507 	return *this; 	
   508       }
   509       int operator--(int) {
   510 	int value = _map[_key];
   511 	_map.set(_key, value - 1); 
   512 	return value; 	
   513       }
   514       Reference& operator+=(int value) { 
   515 	_map.set(_key, _map[_key] + value); 
   516 	return *this;
   517       }
   518       Reference& operator-=(int value) { 
   519 	_map.set(_key, _map[_key] - value); 
   520 	return *this;
   521       }
   522       Reference& operator*=(int value) { 
   523 	_map.set(_key, _map[_key] * value); 
   524 	return *this;
   525       }
   526       Reference& operator/=(int value) { 
   527 	_map.set(_key, _map[_key] / value); 
   528 	return *this;
   529       }
   530       Reference& operator%=(int value) { 
   531 	_map.set(_key, _map[_key] % value); 
   532 	return *this;
   533       }
   534       Reference& operator&=(int value) { 
   535 	_map.set(_key, _map[_key] & value); 
   536 	return *this;
   537       }
   538       Reference& operator|=(int value) { 
   539 	_map.set(_key, _map[_key] | value); 
   540 	return *this;
   541       }
   542       Reference& operator^=(int value) { 
   543 	_map.set(_key, _map[_key] ^ value); 
   544 	return *this;
   545       }
   546       Reference& operator<<=(int value) { 
   547 	_map.set(_key, _map[_key] << value); 
   548 	return *this;
   549       }
   550       Reference& operator>>=(int value) { 
   551 	_map.set(_key, _map[_key] >> value); 
   552 	return *this;
   553       }
   554 
   555     private:
   556       Key _key;
   557       IterableIntMap& _map; 
   558     };
   559 
   560     /// The const reference type.    
   561     typedef const Value& ConstReference;
   562 
   563     /// \brief Gives back the maximal value plus one.
   564     ///
   565     /// Gives back the maximal value plus one.
   566     unsigned int size() const {
   567       return first.size();
   568     }
   569     
   570     /// \brief Set operation of the map.
   571     ///
   572     /// Set operation of the map.
   573     void set(const Key& key, const Value& value) {
   574       unlace(key);
   575       Parent::operator[](key).value = value;
   576       lace(key);
   577     }
   578 
   579     /// \brief Const subscript operator of the map.
   580     ///
   581     /// Const subscript operator of the map.
   582     const Value& operator[](const Key& key) const {
   583       return Parent::operator[](key).value;
   584     }
   585 
   586     /// \brief Subscript operator of the map.
   587     ///
   588     /// Subscript operator of the map.
   589     Reference operator[](const Key& key) {
   590       return Reference(*this, key);
   591     }
   592 
   593     /// \brief Iterator for the keys with the same value.
   594     ///
   595     /// Iterator for the keys with the same value. It works
   596     /// like a graph item iterator in the map, it can be converted
   597     /// the item type of the map, incremented with \c ++ operator, and
   598     /// if the iterator leave the last valid item it will be equal to 
   599     /// \c INVALID.
   600     class ItemIt : public _Item {
   601     public:
   602       typedef _Item Parent;
   603 
   604       /// \brief Invalid constructor \& conversion.
   605       ///
   606       /// This constructor initializes the item to be invalid.
   607       /// \sa Invalid for more details.
   608       ItemIt(Invalid) : Parent(INVALID), _map(0) {}
   609 
   610       /// \brief Creates an iterator with a value.
   611       ///
   612       /// Creates an iterator with a value. It iterates on the 
   613       /// keys which have the given value.
   614       /// \param map The IterableIntMap
   615       /// \param value The value
   616       ItemIt(const IterableIntMap& map, int value) : _map(&map) {
   617 	if (value < 0 || value >= (int)_map->first.size()) {	  
   618 	  Parent::operator=(INVALID);
   619 	} else {
   620 	  Parent::operator=(_map->first[value]);
   621 	}
   622       } 
   623 
   624       /// \brief Increment operator.
   625       ///
   626       /// Increment Operator.
   627       ItemIt& operator++() {
   628 	Parent::operator=(_map->IterableIntMap::Parent::
   629 			  operator[](static_cast<Parent&>(*this)).next);
   630 	return *this;
   631       }
   632 
   633 
   634     private:
   635       const IterableIntMap* _map;
   636     };
   637 
   638   protected:
   639     
   640     virtual void erase(const Key& key) {
   641       unlace(key);
   642       Parent::erase(key);
   643     }
   644 
   645     virtual void erase(const std::vector<Key>& keys) {
   646       for (int i = 0; i < (int)keys.size(); ++i) {
   647         unlace(keys[i]);
   648       }
   649       Parent::erase(keys);
   650     }
   651 
   652     virtual void clear() {
   653       first.clear();
   654       Parent::clear();
   655     }
   656 
   657   private:
   658     std::vector<_Item> first;
   659   };
   660 
   661   namespace _iterable_maps_bits {
   662     template <typename Item, typename Value>
   663     struct IterableValueMapNode {
   664       IterableValueMapNode(Value _value = Value()) : value(_value) {}
   665       Item prev, next;
   666       Value value;
   667     };
   668   }
   669 
   670   ///\ingroup graph_maps
   671   ///
   672   /// \brief Dynamic iterable map for comparable values.
   673   ///
   674   /// This class provides a special graph map type which can store
   675   /// for each graph item(node, edge, etc.) a value. For each
   676   /// value it is possible to iterate on the keys which mapped to the 
   677   /// given value. The type stores for each value a linked list with
   678   /// the items which mapped to the value, and the values are stored
   679   /// in balanced binary tree. The values of the map can be accessed
   680   /// with stl compatible forward iterator.
   681   ///
   682   /// This type is not reference map so it cannot be modified with
   683   /// the subscription operator.
   684   ///
   685   /// \see InvertableMap
   686   /// 
   687   /// \param _Graph The graph type.
   688   /// \param _Item One of the graph's item type, the key of the map.
   689   /// \param _Value Any comparable value type.
   690   template <typename _Graph, typename _Item, typename _Value>
   691   class IterableValueMap 
   692     : protected MapExtender<DefaultMap<_Graph, _Item, _iterable_maps_bits::
   693                                        IterableValueMapNode<_Item, _Value> > >{
   694   public:
   695     typedef MapExtender<DefaultMap<_Graph, _Item, _iterable_maps_bits::
   696                                    IterableValueMapNode<_Item, _Value> > >
   697     Parent;
   698 
   699     /// The key type
   700     typedef _Item Key;
   701     /// The value type
   702     typedef _Value Value;
   703     /// The graph type
   704     typedef _Graph Graph;
   705 
   706   public:
   707 
   708     /// \brief Constructor of the Map with a given value.
   709     ///
   710     /// Constructor of the Map with a given value.
   711     explicit IterableValueMap(const Graph& graph, 
   712                               const Value& value = Value()) 
   713       : Parent(graph, _iterable_maps_bits::
   714                IterableValueMapNode<_Item, _Value>(value)) {
   715       for (typename Parent::ItemIt it(*this); it != INVALID; ++it) {
   716         lace(it);
   717       }
   718     }
   719 
   720   protected:
   721     
   722     void unlace(const Key& key) {
   723       typename Parent::Value& node = Parent::operator[](key);
   724       if (node.prev != INVALID) {
   725 	Parent::operator[](node.prev).next = node.next;	
   726       } else {
   727         if (node.next != INVALID) {
   728           first[node.value] = node.next;
   729         } else {
   730           first.erase(node.value);
   731         }
   732       }
   733       if (node.next != INVALID) {
   734 	Parent::operator[](node.next).prev = node.prev;
   735       }
   736     }
   737 
   738     void lace(const Key& key) {
   739       typename Parent::Value& node = Parent::operator[](key);
   740       typename std::map<Value, Key>::iterator it = first.find(node.value);
   741       if (it == first.end()) {
   742         node.prev = node.next = INVALID;
   743         if (node.next != INVALID) {
   744           Parent::operator[](node.next).prev = key;	
   745         }
   746         first.insert(make_pair(node.value, key));
   747       } else {
   748         node.prev = INVALID;
   749         node.next = it->second;
   750         if (node.next != INVALID) {
   751           Parent::operator[](node.next).prev = key;	
   752         }
   753         it->second = key;
   754       }
   755     }
   756 
   757   public:
   758 
   759     /// \brief Forward iterator for values.
   760     ///
   761     /// This iterator is an stl compatible forward
   762     /// iterator on the values of the map. The values can
   763     /// be accessed in the [beginValue, endValue) range.
   764     ///
   765     class ValueIterator 
   766       : public std::iterator<std::forward_iterator_tag, Value> {
   767       friend class IterableValueMap;
   768     private:
   769       ValueIterator(typename std::map<Value, Key>::const_iterator _it) 
   770         : it(_it) {}
   771     public:
   772       
   773       ValueIterator() {}
   774 
   775       ValueIterator& operator++() { ++it; return *this; }
   776       ValueIterator operator++(int) { 
   777         ValueIterator tmp(*this); 
   778         operator++();
   779         return tmp; 
   780       }
   781 
   782       const Value& operator*() const { return it->first; }
   783       const Value* operator->() const { return &(it->first); }
   784 
   785       bool operator==(ValueIterator jt) const { return it == jt.it; }
   786       bool operator!=(ValueIterator jt) const { return it != jt.it; }
   787       
   788     private:
   789       typename std::map<Value, Key>::const_iterator it;
   790     };
   791 
   792     /// \brief Returns an iterator to the first value.
   793     ///
   794     /// Returns an stl compatible iterator to the 
   795     /// first value of the map. The values of the
   796     /// map can be accessed in the [beginValue, endValue)
   797     /// range.
   798     ValueIterator beginValue() const {
   799       return ValueIterator(first.begin());
   800     }
   801 
   802     /// \brief Returns an iterator after the last value.
   803     ///
   804     /// Returns an stl compatible iterator after the 
   805     /// last value of the map. The values of the
   806     /// map can be accessed in the [beginValue, endValue)
   807     /// range.
   808     ValueIterator endValue() const {
   809       return ValueIterator(first.end());
   810     }
   811 
   812     /// \brief Set operation of the map.
   813     ///
   814     /// Set operation of the map.
   815     void set(const Key& key, const Value& value) {
   816       unlace(key);
   817       Parent::operator[](key).value = value;
   818       lace(key);
   819     }
   820 
   821     /// \brief Const subscript operator of the map.
   822     ///
   823     /// Const subscript operator of the map.
   824     const Value& operator[](const Key& key) const {
   825       return Parent::operator[](key).value;
   826     }
   827 
   828     /// \brief Iterator for the keys with the same value.
   829     ///
   830     /// Iterator for the keys with the same value. It works
   831     /// like a graph item iterator in the map, it can be converted
   832     /// the item type of the map, incremented with \c ++ operator, and
   833     /// if the iterator leave the last valid item it will be equal to 
   834     /// \c INVALID.
   835     class ItemIt : public _Item {
   836     public:
   837       typedef _Item Parent;
   838 
   839       /// \brief Invalid constructor \& conversion.
   840       ///
   841       /// This constructor initializes the item to be invalid.
   842       /// \sa Invalid for more details.
   843       ItemIt(Invalid) : Parent(INVALID), _map(0) {}
   844 
   845       /// \brief Creates an iterator with a value.
   846       ///
   847       /// Creates an iterator with a value. It iterates on the 
   848       /// keys which have the given value.
   849       /// \param map The IterableValueMap
   850       /// \param value The value
   851       ItemIt(const IterableValueMap& map, const Value& value) : _map(&map) {
   852         typename std::map<Value, Key>::const_iterator it = 
   853           map.first.find(value); 
   854 	if (it == map.first.end()) {	  
   855 	  Parent::operator=(INVALID);
   856 	} else {
   857 	  Parent::operator=(it->second);
   858 	}
   859       } 
   860 
   861       /// \brief Increment operator.
   862       ///
   863       /// Increment Operator.
   864       ItemIt& operator++() {
   865 	Parent::operator=(_map->IterableValueMap::Parent::
   866 			  operator[](static_cast<Parent&>(*this)).next);
   867 	return *this;
   868       }
   869 
   870 
   871     private:
   872       const IterableValueMap* _map;
   873     };
   874 
   875   protected:
   876     
   877     virtual void add(const Key& key) {
   878       Parent::add(key);
   879       unlace(key);
   880     }
   881 
   882     virtual void add(const std::vector<Key>& keys) {
   883       Parent::add(keys);
   884       for (int i = 0; i < (int)keys.size(); ++i) {
   885         lace(keys[i]);
   886       }
   887     }
   888 
   889     virtual void erase(const Key& key) {
   890       unlace(key);
   891       Parent::erase(key);
   892     }
   893 
   894     virtual void erase(const std::vector<Key>& keys) {
   895       for (int i = 0; i < (int)keys.size(); ++i) {
   896         unlace(keys[i]);
   897       }
   898       Parent::erase(keys);
   899     }
   900 
   901     virtual void build() {
   902       Parent::build();
   903       for (typename Parent::ItemIt it(*this); it != INVALID; ++it) {
   904         lace(it);
   905       }
   906     }
   907 
   908     virtual void clear() {
   909       first.clear();
   910       Parent::clear();
   911     }
   912 
   913   private:
   914     std::map<Value, Key> first;
   915   };
   916 
   917   /// @}
   918 }