diff -r c35afa9e89e7 -r ef88c0a30f85 lemon/maps.h
--- a/lemon/maps.h	Mon Jan 12 23:11:39 2009 +0100
+++ b/lemon/maps.h	Thu Nov 05 15:48:01 2009 +0100
@@ -22,6 +22,7 @@
 #include <iterator>
 #include <functional>
 #include <vector>
+#include <map>
 
 #include <lemon/core.h>
 
@@ -29,8 +30,6 @@
 ///\ingroup maps
 ///\brief Miscellaneous property maps
 
-#include <map>
-
 namespace lemon {
 
   /// \addtogroup maps
@@ -57,15 +56,16 @@
   /// its type definitions, or if you have to provide a writable map,
   /// but data written to it is not required (i.e. it will be sent to
   /// <tt>/dev/null</tt>).
-  /// It conforms the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
+  /// It conforms to the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
   ///
   /// \sa ConstMap
   template<typename K, typename V>
   class NullMap : public MapBase<K, V> {
   public:
-    typedef MapBase<K, V> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef K Key;
+    ///\e
+    typedef V Value;
 
     /// Gives back a default constructed element.
     Value operator[](const Key&) const { return Value(); }
@@ -89,7 +89,7 @@
   /// value to each key.
   ///
   /// In other aspects it is equivalent to \c NullMap.
-  /// So it conforms the \ref concepts::ReadWriteMap "ReadWriteMap"
+  /// So it conforms to the \ref concepts::ReadWriteMap "ReadWriteMap"
   /// concept, but it absorbs the data written to it.
   ///
   /// The simplest way of using this map is through the constMap()
@@ -102,9 +102,10 @@
   private:
     V _value;
   public:
-    typedef MapBase<K, V> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef K Key;
+    ///\e
+    typedef V Value;
 
     /// Default constructor
 
@@ -157,7 +158,7 @@
   /// value to each key.
   ///
   /// In other aspects it is equivalent to \c NullMap.
-  /// So it conforms the \ref concepts::ReadWriteMap "ReadWriteMap"
+  /// So it conforms to the \ref concepts::ReadWriteMap "ReadWriteMap"
   /// concept, but it absorbs the data written to it.
   ///
   /// The simplest way of using this map is through the constMap()
@@ -168,9 +169,10 @@
   template<typename K, typename V, V v>
   class ConstMap<K, Const<V, v> > : public MapBase<K, V> {
   public:
-    typedef MapBase<K, V> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef K Key;
+    ///\e
+    typedef V Value;
 
     /// Constructor.
     ConstMap() {}
@@ -202,9 +204,10 @@
   template <typename T>
   class IdentityMap : public MapBase<T, T> {
   public:
-    typedef MapBase<T, T> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef T Key;
+    ///\e
+    typedef T Value;
 
     /// Gives back the given value without any modification.
     Value operator[](const Key &k) const {
@@ -229,7 +232,7 @@
   /// values to integer keys from the range <tt>[0..size-1]</tt>.
   /// It can be used with some data structures, for example
   /// \c UnionFind, \c BinHeap, when the used items are small
-  /// integers. This map conforms the \ref concepts::ReferenceMap
+  /// integers. This map conforms to the \ref concepts::ReferenceMap
   /// "ReferenceMap" concept.
   ///
   /// The simplest way of using this map is through the rangeMap()
@@ -245,11 +248,10 @@
 
   public:
 
-    typedef MapBase<int, V> Parent;
     /// Key type
-    typedef typename Parent::Key Key;
+    typedef int Key;
     /// Value type
-    typedef typename Parent::Value Value;
+    typedef V Value;
     /// Reference type
     typedef typename Vector::reference Reference;
     /// Const reference type
@@ -338,7 +340,7 @@
   /// that you can specify a default value for the keys that are not
   /// stored actually. This value can be different from the default
   /// contructed value (i.e. \c %Value()).
-  /// This type conforms the \ref concepts::ReferenceMap "ReferenceMap"
+  /// This type conforms to the \ref concepts::ReferenceMap "ReferenceMap"
   /// concept.
   ///
   /// This map is useful if a default value should be assigned to most of
@@ -353,17 +355,16 @@
   ///
   /// The simplest way of using this map is through the sparseMap()
   /// function.
-  template <typename K, typename V, typename Compare = std::less<K> >
+  template <typename K, typename V, typename Comp = std::less<K> >
   class SparseMap : public MapBase<K, V> {
     template <typename K1, typename V1, typename C1>
     friend class SparseMap;
   public:
 
-    typedef MapBase<K, V> Parent;
     /// Key type
-    typedef typename Parent::Key Key;
+    typedef K Key;
     /// Value type
-    typedef typename Parent::Value Value;
+    typedef V Value;
     /// Reference type
     typedef Value& Reference;
     /// Const reference type
@@ -373,7 +374,7 @@
 
   private:
 
-    typedef std::map<K, V, Compare> Map;
+    typedef std::map<K, V, Comp> Map;
     Map _map;
     Value _value;
 
@@ -489,14 +490,15 @@
     const M1 &_m1;
     const M2 &_m2;
   public:
-    typedef MapBase<typename M2::Key, typename M1::Value> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M2::Key Key;
+    ///\e
+    typedef typename M1::Value Value;
 
     /// Constructor
     ComposeMap(const M1 &m1, const M2 &m2) : _m1(m1), _m2(m2) {}
 
-    /// \e
+    ///\e
     typename MapTraits<M1>::ConstReturnValue
     operator[](const Key &k) const { return _m1[_m2[k]]; }
   };
@@ -545,14 +547,15 @@
     const M2 &_m2;
     F _f;
   public:
-    typedef MapBase<typename M1::Key, V> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M1::Key Key;
+    ///\e
+    typedef V Value;
 
     /// Constructor
     CombineMap(const M1 &m1, const M2 &m2, const F &f = F())
       : _m1(m1), _m2(m2), _f(f) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return _f(_m1[k],_m2[k]); }
   };
 
@@ -615,13 +618,14 @@
   class FunctorToMap : public MapBase<K, V> {
     F _f;
   public:
-    typedef MapBase<K, V> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef K Key;
+    ///\e
+    typedef V Value;
 
     /// Constructor
     FunctorToMap(const F &f = F()) : _f(f) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return _f(k); }
   };
 
@@ -669,18 +673,19 @@
   class MapToFunctor : public MapBase<typename M::Key, typename M::Value> {
     const M &_m;
   public:
-    typedef MapBase<typename M::Key, typename M::Value> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
-
-    typedef typename Parent::Key argument_type;
-    typedef typename Parent::Value result_type;
+    ///\e
+    typedef typename M::Key Key;
+    ///\e
+    typedef typename M::Value Value;
+
+    typedef typename M::Key argument_type;
+    typedef typename M::Value result_type;
 
     /// Constructor
     MapToFunctor(const M &m) : _m(m) {}
-    /// \e
+    ///\e
     Value operator()(const Key &k) const { return _m[k]; }
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return _m[k]; }
   };
 
@@ -701,7 +706,7 @@
   /// "readable map" to another type using the default conversion.
   /// The \c Key type of it is inherited from \c M and the \c Value
   /// type is \c V.
-  /// This type conforms the \ref concepts::ReadMap "ReadMap" concept.
+  /// This type conforms to the \ref concepts::ReadMap "ReadMap" concept.
   ///
   /// The simplest way of using this map is through the convertMap()
   /// function.
@@ -709,9 +714,10 @@
   class ConvertMap : public MapBase<typename M::Key, V> {
     const M &_m;
   public:
-    typedef MapBase<typename M::Key, V> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M::Key Key;
+    ///\e
+    typedef V Value;
 
     /// Constructor
 
@@ -719,7 +725,7 @@
     /// \param m The underlying map.
     ConvertMap(const M &m) : _m(m) {}
 
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return _m[k]; }
   };
 
@@ -751,9 +757,10 @@
     M1 &_m1;
     M2 &_m2;
   public:
-    typedef MapBase<typename M1::Key, typename M1::Value> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M1::Key Key;
+    ///\e
+    typedef typename M1::Value Value;
 
     /// Constructor
     ForkMap(M1 &m1, M2 &m2) : _m1(m1), _m2(m2) {}
@@ -797,13 +804,14 @@
     const M1 &_m1;
     const M2 &_m2;
   public:
-    typedef MapBase<typename M1::Key, typename M1::Value> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M1::Key Key;
+    ///\e
+    typedef typename M1::Value Value;
 
     /// Constructor
     AddMap(const M1 &m1, const M2 &m2) : _m1(m1), _m2(m2) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return _m1[k]+_m2[k]; }
   };
 
@@ -845,13 +853,14 @@
     const M1 &_m1;
     const M2 &_m2;
   public:
-    typedef MapBase<typename M1::Key, typename M1::Value> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M1::Key Key;
+    ///\e
+    typedef typename M1::Value Value;
 
     /// Constructor
     SubMap(const M1 &m1, const M2 &m2) : _m1(m1), _m2(m2) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return _m1[k]-_m2[k]; }
   };
 
@@ -894,13 +903,14 @@
     const M1 &_m1;
     const M2 &_m2;
   public:
-    typedef MapBase<typename M1::Key, typename M1::Value> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M1::Key Key;
+    ///\e
+    typedef typename M1::Value Value;
 
     /// Constructor
     MulMap(const M1 &m1,const M2 &m2) : _m1(m1), _m2(m2) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return _m1[k]*_m2[k]; }
   };
 
@@ -942,13 +952,14 @@
     const M1 &_m1;
     const M2 &_m2;
   public:
-    typedef MapBase<typename M1::Key, typename M1::Value> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M1::Key Key;
+    ///\e
+    typedef typename M1::Value Value;
 
     /// Constructor
     DivMap(const M1 &m1,const M2 &m2) : _m1(m1), _m2(m2) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return _m1[k]/_m2[k]; }
   };
 
@@ -992,9 +1003,10 @@
     const M &_m;
     C _v;
   public:
-    typedef MapBase<typename M::Key, typename M::Value> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M::Key Key;
+    ///\e
+    typedef typename M::Value Value;
 
     /// Constructor
 
@@ -1002,7 +1014,7 @@
     /// \param m The undelying map.
     /// \param v The constant value.
     ShiftMap(const M &m, const C &v) : _m(m), _v(v) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return _m[k]+_v; }
   };
 
@@ -1022,9 +1034,10 @@
     M &_m;
     C _v;
   public:
-    typedef MapBase<typename M::Key, typename M::Value> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M::Key Key;
+    ///\e
+    typedef typename M::Value Value;
 
     /// Constructor
 
@@ -1032,9 +1045,9 @@
     /// \param m The undelying map.
     /// \param v The constant value.
     ShiftWriteMap(M &m, const C &v) : _m(m), _v(v) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return _m[k]+_v; }
-    /// \e
+    ///\e
     void set(const Key &k, const Value &v) { _m.set(k, v-_v); }
   };
 
@@ -1093,9 +1106,10 @@
     const M &_m;
     C _v;
   public:
-    typedef MapBase<typename M::Key, typename M::Value> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M::Key Key;
+    ///\e
+    typedef typename M::Value Value;
 
     /// Constructor
 
@@ -1103,7 +1117,7 @@
     /// \param m The undelying map.
     /// \param v The constant value.
     ScaleMap(const M &m, const C &v) : _m(m), _v(v) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return _v*_m[k]; }
   };
 
@@ -1124,9 +1138,10 @@
     M &_m;
     C _v;
   public:
-    typedef MapBase<typename M::Key, typename M::Value> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M::Key Key;
+    ///\e
+    typedef typename M::Value Value;
 
     /// Constructor
 
@@ -1134,9 +1149,9 @@
     /// \param m The undelying map.
     /// \param v The constant value.
     ScaleWriteMap(M &m, const C &v) : _m(m), _v(v) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return _v*_m[k]; }
-    /// \e
+    ///\e
     void set(const Key &k, const Value &v) { _m.set(k, v/_v); }
   };
 
@@ -1193,13 +1208,14 @@
   class NegMap : public MapBase<typename M::Key, typename M::Value> {
     const M& _m;
   public:
-    typedef MapBase<typename M::Key, typename M::Value> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M::Key Key;
+    ///\e
+    typedef typename M::Value Value;
 
     /// Constructor
     NegMap(const M &m) : _m(m) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return -_m[k]; }
   };
 
@@ -1228,15 +1244,16 @@
   class NegWriteMap : public MapBase<typename M::Key, typename M::Value> {
     M &_m;
   public:
-    typedef MapBase<typename M::Key, typename M::Value> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M::Key Key;
+    ///\e
+    typedef typename M::Value Value;
 
     /// Constructor
     NegWriteMap(M &m) : _m(m) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return -_m[k]; }
-    /// \e
+    ///\e
     void set(const Key &k, const Value &v) { _m.set(k, -v); }
   };
 
@@ -1282,13 +1299,14 @@
   class AbsMap : public MapBase<typename M::Key, typename M::Value> {
     const M &_m;
   public:
-    typedef MapBase<typename M::Key, typename M::Value> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M::Key Key;
+    ///\e
+    typedef typename M::Value Value;
 
     /// Constructor
     AbsMap(const M &m) : _m(m) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const {
       Value tmp = _m[k];
       return tmp >= 0 ? tmp : -tmp;
@@ -1337,9 +1355,10 @@
   template <typename K>
   class TrueMap : public MapBase<K, bool> {
   public:
-    typedef MapBase<K, bool> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef K Key;
+    ///\e
+    typedef bool Value;
 
     /// Gives back \c true.
     Value operator[](const Key&) const { return true; }
@@ -1374,9 +1393,10 @@
   template <typename K>
   class FalseMap : public MapBase<K, bool> {
   public:
-    typedef MapBase<K, bool> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef K Key;
+    ///\e
+    typedef bool Value;
 
     /// Gives back \c false.
     Value operator[](const Key&) const { return false; }
@@ -1419,13 +1439,14 @@
     const M1 &_m1;
     const M2 &_m2;
   public:
-    typedef MapBase<typename M1::Key, bool> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M1::Key Key;
+    ///\e
+    typedef bool Value;
 
     /// Constructor
     AndMap(const M1 &m1, const M2 &m2) : _m1(m1), _m2(m2) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return _m1[k]&&_m2[k]; }
   };
 
@@ -1467,13 +1488,14 @@
     const M1 &_m1;
     const M2 &_m2;
   public:
-    typedef MapBase<typename M1::Key, bool> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M1::Key Key;
+    ///\e
+    typedef bool Value;
 
     /// Constructor
     OrMap(const M1 &m1, const M2 &m2) : _m1(m1), _m2(m2) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return _m1[k]||_m2[k]; }
   };
 
@@ -1506,13 +1528,14 @@
   class NotMap : public MapBase<typename M::Key, bool> {
     const M &_m;
   public:
-    typedef MapBase<typename M::Key, bool> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M::Key Key;
+    ///\e
+    typedef bool Value;
 
     /// Constructor
     NotMap(const M &m) : _m(m) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return !_m[k]; }
   };
 
@@ -1532,15 +1555,16 @@
   class NotWriteMap : public MapBase<typename M::Key, bool> {
     M &_m;
   public:
-    typedef MapBase<typename M::Key, bool> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M::Key Key;
+    ///\e
+    typedef bool Value;
 
     /// Constructor
     NotWriteMap(M &m) : _m(m) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return !_m[k]; }
-    /// \e
+    ///\e
     void set(const Key &k, bool v) { _m.set(k, !v); }
   };
 
@@ -1595,13 +1619,14 @@
     const M1 &_m1;
     const M2 &_m2;
   public:
-    typedef MapBase<typename M1::Key, bool> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M1::Key Key;
+    ///\e
+    typedef bool Value;
 
     /// Constructor
     EqualMap(const M1 &m1, const M2 &m2) : _m1(m1), _m2(m2) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return _m1[k]==_m2[k]; }
   };
 
@@ -1643,13 +1668,14 @@
     const M1 &_m1;
     const M2 &_m2;
   public:
-    typedef MapBase<typename M1::Key, bool> Parent;
-    typedef typename Parent::Key Key;
-    typedef typename Parent::Value Value;
+    ///\e
+    typedef typename M1::Key Key;
+    ///\e
+    typedef bool Value;
 
     /// Constructor
     LessMap(const M1 &m1, const M2 &m2) : _m1(m1), _m2(m2) {}
-    /// \e
+    ///\e
     Value operator[](const Key &k) const { return _m1[k]<_m2[k]; }
   };
 
@@ -1705,24 +1731,27 @@
   /// The simplest way of using this map is through the loggerBoolMap()
   /// function.
   ///
-  /// \tparam It The type of the iterator.
-  /// \tparam Ke The key type of the map. The default value set
+  /// \tparam IT The type of the iterator.
+  /// \tparam KEY The key type of the map. The default value set
   /// according to the iterator type should work in most cases.
   ///
   /// \note The container of the iterator must contain enough space
   /// for the elements or the iterator should be an inserter iterator.
 #ifdef DOXYGEN
-  template <typename It, typename Ke>
+  template <typename IT, typename KEY>
 #else
-  template <typename It,
-            typename Ke=typename _maps_bits::IteratorTraits<It>::Value>
+  template <typename IT,
+            typename KEY = typename _maps_bits::IteratorTraits<IT>::Value>
 #endif
-  class LoggerBoolMap {
+  class LoggerBoolMap : public MapBase<KEY, bool> {
   public:
-    typedef It Iterator;
-
-    typedef Ke Key;
+
+    ///\e
+    typedef KEY Key;
+    ///\e
     typedef bool Value;
+    ///\e
+    typedef IT Iterator;
 
     /// Constructor
     LoggerBoolMap(Iterator it)
@@ -1760,11 +1789,11 @@
   /// order of Dfs algorithm, as the following examples show.
   /// \code
   ///   std::vector<Node> v;
-  ///   dfs(g,s).processedMap(loggerBoolMap(std::back_inserter(v))).run();
+  ///   dfs(g).processedMap(loggerBoolMap(std::back_inserter(v))).run(s);
   /// \endcode
   /// \code
   ///   std::vector<Node> v(countNodes(g));
-  ///   dfs(g,s).processedMap(loggerBoolMap(v.begin())).run();
+  ///   dfs(g).processedMap(loggerBoolMap(v.begin())).run(s);
   /// \endcode
   ///
   /// \note The container of the iterator must contain enough space
@@ -1785,23 +1814,36 @@
   /// \addtogroup graph_maps
   /// @{
 
-  /// Provides an immutable and unique id for each item in the graph.
-
-  /// The IdMap class provides a unique and immutable id for each item of the
-  /// same type (e.g. node) in the graph. This id is <ul><li>\b unique:
-  /// different items (nodes) get different ids <li>\b immutable: the id of an
-  /// item (node) does not change (even if you delete other nodes).  </ul>
-  /// Through this map you get access (i.e. can read) the inner id values of
-  /// the items stored in the graph. This map can be inverted with its member
-  /// class \c InverseMap or with the \c operator() member.
+  /// \brief Provides an immutable and unique id for each item in a graph.
   ///
-  template <typename _Graph, typename _Item>
-  class IdMap {
+  /// IdMap provides a unique and immutable id for each item of the
+  /// same type (\c Node, \c Arc or \c Edge) in a graph. This id is
+  ///  - \b unique: different items get different ids,
+  ///  - \b immutable: the id of an item does not change (even if you
+  ///    delete other nodes).
+  ///
+  /// Using this map you get access (i.e. can read) the inner id values of
+  /// the items stored in the graph, which is returned by the \c id()
+  /// function of the graph. This map can be inverted with its member
+  /// class \c InverseMap or with the \c operator()() member.
+  ///
+  /// \tparam GR The graph type.
+  /// \tparam K The key type of the map (\c GR::Node, \c GR::Arc or
+  /// \c GR::Edge).
+  ///
+  /// \see RangeIdMap
+  template <typename GR, typename K>
+  class IdMap : public MapBase<K, int> {
   public:
-    typedef _Graph Graph;
+    /// The graph type of IdMap.
+    typedef GR Graph;
+    typedef GR Digraph;
+    /// The key type of IdMap (\c Node, \c Arc or \c Edge).
+    typedef K Item;
+    /// The key type of IdMap (\c Node, \c Arc or \c Edge).
+    typedef K Key;
+    /// The value type of IdMap.
     typedef int Value;
-    typedef _Item Item;
-    typedef _Item Key;
 
     /// \brief Constructor.
     ///
@@ -1813,9 +1855,9 @@
     /// Gives back the immutable and unique \e id of the item.
     int operator[](const Item& item) const { return _graph->id(item);}
 
-    /// \brief Gives back the item by its id.
+    /// \brief Gives back the \e item by its id.
     ///
-    /// Gives back the item by its id.
+    /// Gives back the \e item by its id.
     Item operator()(int id) { return _graph->fromId(id, Item()); }
 
   private:
@@ -1823,9 +1865,11 @@
 
   public:
 
-    /// \brief The class represents the inverse of its owner (IdMap).
+    /// \brief The inverse map type of IdMap.
     ///
-    /// The class represents the inverse of its owner (IdMap).
+    /// The inverse map type of IdMap. The subscript operator gives back
+    /// an item by its id.
+    /// This type conforms to the \ref concepts::ReadMap "ReadMap" concept.
     /// \see inverse()
     class InverseMap {
     public:
@@ -1840,10 +1884,9 @@
       /// Constructor for creating an id-to-item map.
       explicit InverseMap(const IdMap& map) : _graph(map._graph) {}
 
-      /// \brief Gives back the given item from its id.
+      /// \brief Gives back an item by its id.
       ///
-      /// Gives back the given item from its id.
-      ///
+      /// Gives back an item by its id.
       Item operator[](int id) const { return _graph->fromId(id, Item());}
 
     private:
@@ -1854,165 +1897,220 @@
     ///
     /// Gives back the inverse of the IdMap.
     InverseMap inverse() const { return InverseMap(*_graph);}
-
   };
 
-
-  /// \brief General invertable graph-map type.
-
-  /// This type provides simple invertable graph-maps.
-  /// The InvertableMap wraps an arbitrary ReadWriteMap
-  /// and if a key is set to a new value then store it
-  /// in the inverse map.
+  /// \brief Returns an \c IdMap class.
   ///
-  /// The values of the map can be accessed
-  /// with stl compatible forward iterator.
+  /// This function just returns an \c IdMap class.
+  /// \relates IdMap
+  template <typename K, typename GR>
+  inline IdMap<GR, K> idMap(const GR& graph) {
+    return IdMap<GR, K>(graph);
+  }
+
+  /// \brief General cross reference graph map type.
+
+  /// This class provides simple invertable graph maps.
+  /// It wraps a standard graph map (\c NodeMap, \c ArcMap or \c EdgeMap)
+  /// and if a key is set to a new value, then stores it in the inverse map.
+  /// The graph items can be accessed by their values either using
+  /// \c InverseMap or \c operator()(), and the values of the map can be
+  /// accessed with an STL compatible forward iterator (\c ValueIt).
+  /// 
+  /// This map is intended to be used when all associated values are
+  /// different (the map is actually invertable) or there are only a few
+  /// items with the same value.
+  /// Otherwise consider to use \c IterableValueMap, which is more 
+  /// suitable and more efficient for such cases. It provides iterators
+  /// to traverse the items with the same associated value, however
+  /// it does not have \c InverseMap.
   ///
-  /// \tparam _Graph The graph type.
-  /// \tparam _Item The item type of the graph.
-  /// \tparam _Value The value type of the map.
+  /// This type is not reference map, so it cannot be modified with
+  /// the subscript operator.
+  ///
+  /// \tparam GR The graph type.
+  /// \tparam K The key type of the map (\c GR::Node, \c GR::Arc or
+  /// \c GR::Edge).
+  /// \tparam V The value type of the map.
   ///
   /// \see IterableValueMap
-  template <typename _Graph, typename _Item, typename _Value>
-  class InvertableMap
-    : protected ItemSetTraits<_Graph, _Item>::template Map<_Value>::Type {
+  template <typename GR, typename K, typename V>
+  class CrossRefMap
+    : protected ItemSetTraits<GR, K>::template Map<V>::Type {
   private:
 
-    typedef typename ItemSetTraits<_Graph, _Item>::
-    template Map<_Value>::Type Map;
-    typedef _Graph Graph;
-
-    typedef std::map<_Value, _Item> Container;
+    typedef typename ItemSetTraits<GR, K>::
+      template Map<V>::Type Map;
+
+    typedef std::multimap<V, K> Container;
     Container _inv_map;
 
   public:
 
-    /// The key type of InvertableMap (Node, Arc, Edge).
-    typedef typename Map::Key Key;
-    /// The value type of the InvertableMap.
-    typedef typename Map::Value Value;
+    /// The graph type of CrossRefMap.
+    typedef GR Graph;
+    typedef GR Digraph;
+    /// The key type of CrossRefMap (\c Node, \c Arc or \c Edge).
+    typedef K Item;
+    /// The key type of CrossRefMap (\c Node, \c Arc or \c Edge).
+    typedef K Key;
+    /// The value type of CrossRefMap.
+    typedef V Value;
 
     /// \brief Constructor.
     ///
-    /// Construct a new InvertableMap for the graph.
-    ///
-    explicit InvertableMap(const Graph& graph) : Map(graph) {}
+    /// Construct a new CrossRefMap for the given graph.
+    explicit CrossRefMap(const Graph& graph) : Map(graph) {}
 
     /// \brief Forward iterator for values.
     ///
-    /// This iterator is an stl compatible forward
+    /// This iterator is an STL compatible forward
     /// iterator on the values of the map. The values can
-    /// be accessed in the [beginValue, endValue) range.
-    ///
-    class ValueIterator
+    /// be accessed in the <tt>[beginValue, endValue)</tt> range.
+    /// They are considered with multiplicity, so each value is
+    /// traversed for each item it is assigned to.
+    class ValueIt
       : public std::iterator<std::forward_iterator_tag, Value> {
-      friend class InvertableMap;
+      friend class CrossRefMap;
     private:
-      ValueIterator(typename Container::const_iterator _it)
+      ValueIt(typename Container::const_iterator _it)
         : it(_it) {}
     public:
 
-      ValueIterator() {}
-
-      ValueIterator& operator++() { ++it; return *this; }
-      ValueIterator operator++(int) {
-        ValueIterator tmp(*this);
+      /// Constructor
+      ValueIt() {}
+
+      /// \e
+      ValueIt& operator++() { ++it; return *this; }
+      /// \e
+      ValueIt operator++(int) {
+        ValueIt tmp(*this);
         operator++();
         return tmp;
       }
 
+      /// \e
       const Value& operator*() const { return it->first; }
+      /// \e
       const Value* operator->() const { return &(it->first); }
 
-      bool operator==(ValueIterator jt) const { return it == jt.it; }
-      bool operator!=(ValueIterator jt) const { return it != jt.it; }
+      /// \e
+      bool operator==(ValueIt jt) const { return it == jt.it; }
+      /// \e
+      bool operator!=(ValueIt jt) const { return it != jt.it; }
 
     private:
       typename Container::const_iterator it;
     };
+    
+    /// Alias for \c ValueIt
+    typedef ValueIt ValueIterator;
 
     /// \brief Returns an iterator to the first value.
     ///
-    /// Returns an stl compatible iterator to the
+    /// Returns an STL compatible iterator to the
     /// first value of the map. The values of the
-    /// map can be accessed in the [beginValue, endValue)
+    /// map can be accessed in the <tt>[beginValue, endValue)</tt>
     /// range.
-    ValueIterator beginValue() const {
-      return ValueIterator(_inv_map.begin());
+    ValueIt beginValue() const {
+      return ValueIt(_inv_map.begin());
     }
 
     /// \brief Returns an iterator after the last value.
     ///
-    /// Returns an stl compatible iterator after the
+    /// Returns an STL compatible iterator after the
     /// last value of the map. The values of the
-    /// map can be accessed in the [beginValue, endValue)
+    /// map can be accessed in the <tt>[beginValue, endValue)</tt>
     /// range.
-    ValueIterator endValue() const {
-      return ValueIterator(_inv_map.end());
+    ValueIt endValue() const {
+      return ValueIt(_inv_map.end());
     }
 
-    /// \brief The setter function of the map.
+    /// \brief Sets the value associated with the given key.
     ///
-    /// Sets the mapped value.
+    /// Sets the value associated with the given key.
     void set(const Key& key, const Value& val) {
       Value oldval = Map::operator[](key);
-      typename Container::iterator it = _inv_map.find(oldval);
-      if (it != _inv_map.end() && it->second == key) {
-        _inv_map.erase(it);
+      typename Container::iterator it;
+      for (it = _inv_map.equal_range(oldval).first;
+           it != _inv_map.equal_range(oldval).second; ++it) {
+        if (it->second == key) {
+          _inv_map.erase(it);
+          break;
+        }
       }
-      _inv_map.insert(make_pair(val, key));
+      _inv_map.insert(std::make_pair(val, key));
       Map::set(key, val);
     }
 
-    /// \brief The getter function of the map.
+    /// \brief Returns the value associated with the given key.
     ///
-    /// It gives back the value associated with the key.
+    /// Returns the value associated with the given key.
     typename MapTraits<Map>::ConstReturnValue
     operator[](const Key& key) const {
       return Map::operator[](key);
     }
 
-    /// \brief Gives back the item by its value.
+    /// \brief Gives back an item by its value.
     ///
-    /// Gives back the item by its value.
-    Key operator()(const Value& key) const {
-      typename Container::const_iterator it = _inv_map.find(key);
+    /// This function gives back an item that is assigned to
+    /// the given value or \c INVALID if no such item exists.
+    /// If there are more items with the same associated value,
+    /// only one of them is returned.
+    Key operator()(const Value& val) const {
+      typename Container::const_iterator it = _inv_map.find(val);
       return it != _inv_map.end() ? it->second : INVALID;
     }
+    
+    /// \brief Returns the number of items with the given value.
+    ///
+    /// This function returns the number of items with the given value
+    /// associated with it.
+    int count(const Value &val) const {
+      return _inv_map.count(val);
+    }
 
   protected:
 
-    /// \brief Erase the key from the map.
+    /// \brief Erase the key from the map and the inverse map.
     ///
-    /// Erase the key to the map. It is called by the
+    /// Erase the key from the map and the inverse map. It is called by the
     /// \c AlterationNotifier.
     virtual void erase(const Key& key) {
       Value val = Map::operator[](key);
-      typename Container::iterator it = _inv_map.find(val);
-      if (it != _inv_map.end() && it->second == key) {
-        _inv_map.erase(it);
+      typename Container::iterator it;
+      for (it = _inv_map.equal_range(val).first;
+           it != _inv_map.equal_range(val).second; ++it) {
+        if (it->second == key) {
+          _inv_map.erase(it);
+          break;
+        }
       }
       Map::erase(key);
     }
 
-    /// \brief Erase more keys from the map.
+    /// \brief Erase more keys from the map and the inverse map.
     ///
-    /// Erase more keys from the map. It is called by the
+    /// Erase more keys from the map and the inverse map. It is called by the
     /// \c AlterationNotifier.
     virtual void erase(const std::vector<Key>& keys) {
       for (int i = 0; i < int(keys.size()); ++i) {
         Value val = Map::operator[](keys[i]);
-        typename Container::iterator it = _inv_map.find(val);
-        if (it != _inv_map.end() && it->second == keys[i]) {
-          _inv_map.erase(it);
+        typename Container::iterator it;
+        for (it = _inv_map.equal_range(val).first;
+             it != _inv_map.equal_range(val).second; ++it) {
+          if (it->second == keys[i]) {
+            _inv_map.erase(it);
+            break;
+          }
         }
       }
       Map::erase(keys);
     }
 
-    /// \brief Clear the keys from the map and inverse map.
+    /// \brief Clear the keys from the map and the inverse map.
     ///
-    /// Clear the keys from the map and inverse map. It is called by the
+    /// Clear the keys from the map and the inverse map. It is called by the
     /// \c AlterationNotifier.
     virtual void clear() {
       _inv_map.clear();
@@ -2021,79 +2119,90 @@
 
   public:
 
-    /// \brief The inverse map type.
+    /// \brief The inverse map type of CrossRefMap.
     ///
-    /// The inverse of this map. The subscript operator of the map
-    /// gives back always the item what was last assigned to the value.
+    /// The inverse map type of CrossRefMap. The subscript operator gives
+    /// back an item by its value.
+    /// This type conforms to the \ref concepts::ReadMap "ReadMap" concept.
+    /// \see inverse()
     class InverseMap {
     public:
-      /// \brief Constructor of the InverseMap.
+      /// \brief Constructor
       ///
       /// Constructor of the InverseMap.
-      explicit InverseMap(const InvertableMap& inverted)
+      explicit InverseMap(const CrossRefMap& inverted)
         : _inverted(inverted) {}
 
       /// The value type of the InverseMap.
-      typedef typename InvertableMap::Key Value;
+      typedef typename CrossRefMap::Key Value;
       /// The key type of the InverseMap.
-      typedef typename InvertableMap::Value Key;
+      typedef typename CrossRefMap::Value Key;
 
       /// \brief Subscript operator.
       ///
-      /// Subscript operator. It gives back always the item
-      /// what was last assigned to the value.
+      /// Subscript operator. It gives back an item
+      /// that is assigned to the given value or \c INVALID
+      /// if no such item exists.
       Value operator[](const Key& key) const {
         return _inverted(key);
       }
 
     private:
-      const InvertableMap& _inverted;
+      const CrossRefMap& _inverted;
     };
 
-    /// \brief It gives back the just readable inverse map.
+    /// \brief Gives back the inverse of the map.
     ///
-    /// It gives back the just readable inverse map.
+    /// Gives back the inverse of the CrossRefMap.
     InverseMap inverse() const {
       return InverseMap(*this);
     }
 
   };
 
-  /// \brief Provides a mutable, continuous and unique descriptor for each
-  /// item in the graph.
+  /// \brief Provides continuous and unique id for the
+  /// items of a graph.
   ///
-  /// The DescriptorMap class provides a unique and continuous (but mutable)
-  /// descriptor (id) for each item of the same type (e.g. node) in the
-  /// graph. This id is <ul><li>\b unique: different items (nodes) get
-  /// different ids <li>\b continuous: the range of the ids is the set of
-  /// integers between 0 and \c n-1, where \c n is the number of the items of
-  /// this type (e.g. nodes) (so the id of a node can change if you delete an
-  /// other node, i.e. this id is mutable).  </ul> This map can be inverted
-  /// with its member class \c InverseMap, or with the \c operator() member.
+  /// RangeIdMap provides a unique and continuous
+  /// id for each item of a given type (\c Node, \c Arc or
+  /// \c Edge) in a graph. This id is
+  ///  - \b unique: different items get different ids,
+  ///  - \b continuous: the range of the ids is the set of integers
+  ///    between 0 and \c n-1, where \c n is the number of the items of
+  ///    this type (\c Node, \c Arc or \c Edge).
+  ///  - So, the ids can change when deleting an item of the same type.
   ///
-  /// \tparam _Graph The graph class the \c DescriptorMap belongs to.
-  /// \tparam _Item The Item is the Key of the Map. It may be Node, Arc or
-  /// Edge.
-  template <typename _Graph, typename _Item>
-  class DescriptorMap
-    : protected ItemSetTraits<_Graph, _Item>::template Map<int>::Type {
-
-    typedef _Item Item;
-    typedef typename ItemSetTraits<_Graph, _Item>::template Map<int>::Type Map;
+  /// Thus this id is not (necessarily) the same as what can get using
+  /// the \c id() function of the graph or \ref IdMap.
+  /// This map can be inverted with its member class \c InverseMap,
+  /// or with the \c operator()() member.
+  ///
+  /// \tparam GR The graph type.
+  /// \tparam K The key type of the map (\c GR::Node, \c GR::Arc or
+  /// \c GR::Edge).
+  ///
+  /// \see IdMap
+  template <typename GR, typename K>
+  class RangeIdMap
+    : protected ItemSetTraits<GR, K>::template Map<int>::Type {
+
+    typedef typename ItemSetTraits<GR, K>::template Map<int>::Type Map;
 
   public:
-    /// The graph class of DescriptorMap.
-    typedef _Graph Graph;
-
-    /// The key type of DescriptorMap (Node, Arc, Edge).
-    typedef typename Map::Key Key;
-    /// The value type of DescriptorMap.
-    typedef typename Map::Value Value;
+    /// The graph type of RangeIdMap.
+    typedef GR Graph;
+    typedef GR Digraph;
+    /// The key type of RangeIdMap (\c Node, \c Arc or \c Edge).
+    typedef K Item;
+    /// The key type of RangeIdMap (\c Node, \c Arc or \c Edge).
+    typedef K Key;
+    /// The value type of RangeIdMap.
+    typedef int Value;
 
     /// \brief Constructor.
     ///
-    /// Constructor for descriptor map.
-    explicit DescriptorMap(const Graph& _graph) : Map(_graph) {
+    /// Constructor.
+    explicit RangeIdMap(const Graph& gr) : Map(gr) {
       Item it;
       const typename Map::Notifier* nf = Map::notifier();
       for (nf->first(it); it != INVALID; nf->next(it)) {
@@ -2104,7 +2213,7 @@
 
   protected:
 
-    /// \brief Add a new key to the map.
+    /// \brief Adds a new key to the map.
     ///
     /// Add a new key to the map. It is called by the
     /// \c AlterationNotifier.
@@ -2194,16 +2303,16 @@
       _inv_map[pi] = q;
     }
 
-    /// \brief Gives back the \e descriptor of the item.
+    /// \brief Gives back the \e range \e id of the item
     ///
-    /// Gives back the mutable and unique \e descriptor of the map.
+    /// Gives back the \e range \e id of the item.
     int operator[](const Item& item) const {
       return Map::operator[](item);
     }
 
-    /// \brief Gives back the item by its descriptor.
+    /// \brief Gives back the item belonging to a \e range \e id
     ///
-    /// Gives back th item by its descriptor.
+    /// Gives back the item belonging to the given \e range \e id.
     Item operator()(int id) const {
       return _inv_map[id];
     }
@@ -2214,27 +2323,30 @@
     Container _inv_map;
 
   public:
-    /// \brief The inverse map type of DescriptorMap.
+
+    /// \brief The inverse map type of RangeIdMap.
     ///
-    /// The inverse map type of DescriptorMap.
+    /// The inverse map type of RangeIdMap. The subscript operator gives
+    /// back an item by its \e range \e id.
+    /// This type conforms to the \ref concepts::ReadMap "ReadMap" concept.
     class InverseMap {
     public:
-      /// \brief Constructor of the InverseMap.
+      /// \brief Constructor
       ///
       /// Constructor of the InverseMap.
-      explicit InverseMap(const DescriptorMap& inverted)
+      explicit InverseMap(const RangeIdMap& inverted)
         : _inverted(inverted) {}
 
 
       /// The value type of the InverseMap.
-      typedef typename DescriptorMap::Key Value;
+      typedef typename RangeIdMap::Key Value;
       /// The key type of the InverseMap.
-      typedef typename DescriptorMap::Value Key;
+      typedef typename RangeIdMap::Value Key;
 
       /// \brief Subscript operator.
       ///
       /// Subscript operator. It gives back the item
-      /// that the descriptor belongs to currently.
+      /// that the given \e range \e id currently belongs to.
       Value operator[](const Key& key) const {
         return _inverted(key);
       }
@@ -2247,241 +2359,1134 @@
       }
 
     private:
-      const DescriptorMap& _inverted;
+      const RangeIdMap& _inverted;
     };
 
     /// \brief Gives back the inverse of the map.
     ///
-    /// Gives back the inverse of the map.
+    /// Gives back the inverse of the RangeIdMap.
     const InverseMap inverse() const {
       return InverseMap(*this);
     }
   };
 
-  /// \brief Returns the source of the given arc.
+  /// \brief Returns a \c RangeIdMap class.
   ///
-  /// The SourceMap gives back the source Node of the given arc.
+  /// This function just returns an \c RangeIdMap class.
+  /// \relates RangeIdMap
+  template <typename K, typename GR>
+  inline RangeIdMap<GR, K> rangeIdMap(const GR& graph) {
+    return RangeIdMap<GR, K>(graph);
+  }
+  
+  /// \brief Dynamic iterable \c bool map.
+  ///
+  /// This class provides a special graph map type which can store a
+  /// \c bool value for graph items (\c Node, \c Arc or \c Edge).
+  /// For both \c true and \c false values it is possible to iterate on
+  /// the keys mapped to the value.
+  ///
+  /// This type is a reference map, so it can be modified with the
+  /// subscript operator.
+  ///
+  /// \tparam GR The graph type.
+  /// \tparam K The key type of the map (\c GR::Node, \c GR::Arc or
+  /// \c GR::Edge).
+  ///
+  /// \see IterableIntMap, IterableValueMap
+  /// \see CrossRefMap
+  template <typename GR, typename K>
+  class IterableBoolMap
+    : protected ItemSetTraits<GR, K>::template Map<int>::Type {
+  private:
+    typedef GR Graph;
+
+    typedef typename ItemSetTraits<GR, K>::ItemIt KeyIt;
+    typedef typename ItemSetTraits<GR, K>::template Map<int>::Type Parent;
+
+    std::vector<K> _array;
+    int _sep;
+
+  public:
+
+    /// Indicates that the map is reference map.
+    typedef True ReferenceMapTag;
+
+    /// The key type
+    typedef K Key;
+    /// The value type
+    typedef bool Value;
+    /// The const reference type.
+    typedef const Value& ConstReference;
+
+  private:
+
+    int position(const Key& key) const {
+      return Parent::operator[](key);
+    }
+
+  public:
+
+    /// \brief Reference to the value of the map.
+    ///
+    /// This class is similar to the \c bool type. It can be converted to
+    /// \c bool and it provides the same operators.
+    class Reference {
+      friend class IterableBoolMap;
+    private:
+      Reference(IterableBoolMap& map, const Key& key)
+        : _key(key), _map(map) {}
+    public:
+
+      Reference& operator=(const Reference& value) {
+        _map.set(_key, static_cast<bool>(value));
+         return *this;
+      }
+
+      operator bool() const {
+        return static_cast<const IterableBoolMap&>(_map)[_key];
+      }
+
+      Reference& operator=(bool value) {
+        _map.set(_key, value);
+        return *this;
+      }
+      Reference& operator&=(bool value) {
+        _map.set(_key, _map[_key] & value);
+        return *this;
+      }
+      Reference& operator|=(bool value) {
+        _map.set(_key, _map[_key] | value);
+        return *this;
+      }
+      Reference& operator^=(bool value) {
+        _map.set(_key, _map[_key] ^ value);
+        return *this;
+      }
+    private:
+      Key _key;
+      IterableBoolMap& _map;
+    };
+
+    /// \brief Constructor of the map with a default value.
+    ///
+    /// Constructor of the map with a default value.
+    explicit IterableBoolMap(const Graph& graph, bool def = false)
+      : Parent(graph) {
+      typename Parent::Notifier* nf = Parent::notifier();
+      Key it;
+      for (nf->first(it); it != INVALID; nf->next(it)) {
+        Parent::set(it, _array.size());
+        _array.push_back(it);
+      }
+      _sep = (def ? _array.size() : 0);
+    }
+
+    /// \brief Const subscript operator of the map.
+    ///
+    /// Const subscript operator of the map.
+    bool operator[](const Key& key) const {
+      return position(key) < _sep;
+    }
+
+    /// \brief Subscript operator of the map.
+    ///
+    /// Subscript operator of the map.
+    Reference operator[](const Key& key) {
+      return Reference(*this, key);
+    }
+
+    /// \brief Set operation of the map.
+    ///
+    /// Set operation of the map.
+    void set(const Key& key, bool value) {
+      int pos = position(key);
+      if (value) {
+        if (pos < _sep) return;
+        Key tmp = _array[_sep];
+        _array[_sep] = key;
+        Parent::set(key, _sep);
+        _array[pos] = tmp;
+        Parent::set(tmp, pos);
+        ++_sep;
+      } else {
+        if (pos >= _sep) return;
+        --_sep;
+        Key tmp = _array[_sep];
+        _array[_sep] = key;
+        Parent::set(key, _sep);
+        _array[pos] = tmp;
+        Parent::set(tmp, pos);
+      }
+    }
+
+    /// \brief Set all items.
+    ///
+    /// Set all items in the map.
+    /// \note Constant time operation.
+    void setAll(bool value) {
+      _sep = (value ? _array.size() : 0);
+    }
+
+    /// \brief Returns the number of the keys mapped to \c true.
+    ///
+    /// Returns the number of the keys mapped to \c true.
+    int trueNum() const {
+      return _sep;
+    }
+
+    /// \brief Returns the number of the keys mapped to \c false.
+    ///
+    /// Returns the number of the keys mapped to \c false.
+    int falseNum() const {
+      return _array.size() - _sep;
+    }
+
+    /// \brief Iterator for the keys mapped to \c true.
+    ///
+    /// Iterator for the keys mapped to \c true. It works
+    /// like a graph item iterator, it can be converted to
+    /// the key type of the map, incremented with \c ++ operator, and
+    /// if the iterator leaves the last valid key, it will be equal to
+    /// \c INVALID.
+    class TrueIt : public Key {
+    public:
+      typedef Key Parent;
+
+      /// \brief Creates an iterator.
+      ///
+      /// Creates an iterator. It iterates on the
+      /// keys mapped to \c true.
+      /// \param map The IterableBoolMap.
+      explicit TrueIt(const IterableBoolMap& map)
+        : Parent(map._sep > 0 ? map._array[map._sep - 1] : INVALID),
+          _map(&map) {}
+
+      /// \brief Invalid constructor \& conversion.
+      ///
+      /// This constructor initializes the iterator to be invalid.
+      /// \sa Invalid for more details.
+      TrueIt(Invalid) : Parent(INVALID), _map(0) {}
+
+      /// \brief Increment operator.
+      ///
+      /// Increment operator.
+      TrueIt& operator++() {
+        int pos = _map->position(*this);
+        Parent::operator=(pos > 0 ? _map->_array[pos - 1] : INVALID);
+        return *this;
+      }
+
+    private:
+      const IterableBoolMap* _map;
+    };
+
+    /// \brief Iterator for the keys mapped to \c false.
+    ///
+    /// Iterator for the keys mapped to \c false. It works
+    /// like a graph item iterator, it can be converted to
+    /// the key type of the map, incremented with \c ++ operator, and
+    /// if the iterator leaves the last valid key, it will be equal to
+    /// \c INVALID.
+    class FalseIt : public Key {
+    public:
+      typedef Key Parent;
+
+      /// \brief Creates an iterator.
+      ///
+      /// Creates an iterator. It iterates on the
+      /// keys mapped to \c false.
+      /// \param map The IterableBoolMap.
+      explicit FalseIt(const IterableBoolMap& map)
+        : Parent(map._sep < int(map._array.size()) ?
+                 map._array.back() : INVALID), _map(&map) {}
+
+      /// \brief Invalid constructor \& conversion.
+      ///
+      /// This constructor initializes the iterator to be invalid.
+      /// \sa Invalid for more details.
+      FalseIt(Invalid) : Parent(INVALID), _map(0) {}
+
+      /// \brief Increment operator.
+      ///
+      /// Increment operator.
+      FalseIt& operator++() {
+        int pos = _map->position(*this);
+        Parent::operator=(pos > _map->_sep ? _map->_array[pos - 1] : INVALID);
+        return *this;
+      }
+
+    private:
+      const IterableBoolMap* _map;
+    };
+
+    /// \brief Iterator for the keys mapped to a given value.
+    ///
+    /// Iterator for the keys mapped to a given value. It works
+    /// like a graph item iterator, it can be converted to
+    /// the key type of the map, incremented with \c ++ operator, and
+    /// if the iterator leaves the last valid key, it will be equal to
+    /// \c INVALID.
+    class ItemIt : public Key {
+    public:
+      typedef Key Parent;
+
+      /// \brief Creates an iterator with a value.
+      ///
+      /// Creates an iterator with a value. It iterates on the
+      /// keys mapped to the given value.
+      /// \param map The IterableBoolMap.
+      /// \param value The value.
+      ItemIt(const IterableBoolMap& map, bool value)
+        : Parent(value ? 
+                 (map._sep > 0 ?
+                  map._array[map._sep - 1] : INVALID) :
+                 (map._sep < int(map._array.size()) ?
+                  map._array.back() : INVALID)), _map(&map) {}
+
+      /// \brief Invalid constructor \& conversion.
+      ///
+      /// This constructor initializes the iterator to be invalid.
+      /// \sa Invalid for more details.
+      ItemIt(Invalid) : Parent(INVALID), _map(0) {}
+
+      /// \brief Increment operator.
+      ///
+      /// Increment operator.
+      ItemIt& operator++() {
+        int pos = _map->position(*this);
+        int _sep = pos >= _map->_sep ? _map->_sep : 0;
+        Parent::operator=(pos > _sep ? _map->_array[pos - 1] : INVALID);
+        return *this;
+      }
+
+    private:
+      const IterableBoolMap* _map;
+    };
+
+  protected:
+
+    virtual void add(const Key& key) {
+      Parent::add(key);
+      Parent::set(key, _array.size());
+      _array.push_back(key);
+    }
+
+    virtual void add(const std::vector<Key>& keys) {
+      Parent::add(keys);
+      for (int i = 0; i < int(keys.size()); ++i) {
+        Parent::set(keys[i], _array.size());
+        _array.push_back(keys[i]);
+      }
+    }
+
+    virtual void erase(const Key& key) {
+      int pos = position(key);
+      if (pos < _sep) {
+        --_sep;
+        Parent::set(_array[_sep], pos);
+        _array[pos] = _array[_sep];
+        Parent::set(_array.back(), _sep);
+        _array[_sep] = _array.back();
+        _array.pop_back();
+      } else {
+        Parent::set(_array.back(), pos);
+        _array[pos] = _array.back();
+        _array.pop_back();
+      }
+      Parent::erase(key);
+    }
+
+    virtual void erase(const std::vector<Key>& keys) {
+      for (int i = 0; i < int(keys.size()); ++i) {
+        int pos = position(keys[i]);
+        if (pos < _sep) {
+          --_sep;
+          Parent::set(_array[_sep], pos);
+          _array[pos] = _array[_sep];
+          Parent::set(_array.back(), _sep);
+          _array[_sep] = _array.back();
+          _array.pop_back();
+        } else {
+          Parent::set(_array.back(), pos);
+          _array[pos] = _array.back();
+          _array.pop_back();
+        }
+      }
+      Parent::erase(keys);
+    }
+
+    virtual void build() {
+      Parent::build();
+      typename Parent::Notifier* nf = Parent::notifier();
+      Key it;
+      for (nf->first(it); it != INVALID; nf->next(it)) {
+        Parent::set(it, _array.size());
+        _array.push_back(it);
+      }
+      _sep = 0;
+    }
+
+    virtual void clear() {
+      _array.clear();
+      _sep = 0;
+      Parent::clear();
+    }
+
+  };
+
+
+  namespace _maps_bits {
+    template <typename Item>
+    struct IterableIntMapNode {
+      IterableIntMapNode() : value(-1) {}
+      IterableIntMapNode(int _value) : value(_value) {}
+      Item prev, next;
+      int value;
+    };
+  }
+
+  /// \brief Dynamic iterable integer map.
+  ///
+  /// This class provides a special graph map type which can store an
+  /// integer value for graph items (\c Node, \c Arc or \c Edge).
+  /// For each non-negative value it is possible to iterate on the keys
+  /// mapped to the value.
+  ///
+  /// This map is intended to be used with small integer values, for which
+  /// it is efficient, and supports iteration only for non-negative values.
+  /// If you need large values and/or iteration for negative integers,
+  /// consider to use \ref IterableValueMap instead.
+  ///
+  /// This type is a reference map, so it can be modified with the
+  /// subscript operator.
+  ///
+  /// \note The size of the data structure depends on the largest
+  /// value in the map.
+  ///
+  /// \tparam GR The graph type.
+  /// \tparam K The key type of the map (\c GR::Node, \c GR::Arc or
+  /// \c GR::Edge).
+  ///
+  /// \see IterableBoolMap, IterableValueMap
+  /// \see CrossRefMap
+  template <typename GR, typename K>
+  class IterableIntMap
+    : protected ItemSetTraits<GR, K>::
+        template Map<_maps_bits::IterableIntMapNode<K> >::Type {
+  public:
+    typedef typename ItemSetTraits<GR, K>::
+      template Map<_maps_bits::IterableIntMapNode<K> >::Type Parent;
+
+    /// The key type
+    typedef K Key;
+    /// The value type
+    typedef int Value;
+    /// The graph type
+    typedef GR Graph;
+
+    /// \brief Constructor of the map.
+    ///
+    /// Constructor of the map. It sets all values to -1.
+    explicit IterableIntMap(const Graph& graph)
+      : Parent(graph) {}
+
+    /// \brief Constructor of the map with a given value.
+    ///
+    /// Constructor of the map with a given value.
+    explicit IterableIntMap(const Graph& graph, int value)
+      : Parent(graph, _maps_bits::IterableIntMapNode<K>(value)) {
+      if (value >= 0) {
+        for (typename Parent::ItemIt it(*this); it != INVALID; ++it) {
+          lace(it);
+        }
+      }
+    }
+
+  private:
+
+    void unlace(const Key& key) {
+      typename Parent::Value& node = Parent::operator[](key);
+      if (node.value < 0) return;
+      if (node.prev != INVALID) {
+        Parent::operator[](node.prev).next = node.next;
+      } else {
+        _first[node.value] = node.next;
+      }
+      if (node.next != INVALID) {
+        Parent::operator[](node.next).prev = node.prev;
+      }
+      while (!_first.empty() && _first.back() == INVALID) {
+        _first.pop_back();
+      }
+    }
+
+    void lace(const Key& key) {
+      typename Parent::Value& node = Parent::operator[](key);
+      if (node.value < 0) return;
+      if (node.value >= int(_first.size())) {
+        _first.resize(node.value + 1, INVALID);
+      }
+      node.prev = INVALID;
+      node.next = _first[node.value];
+      if (node.next != INVALID) {
+        Parent::operator[](node.next).prev = key;
+      }
+      _first[node.value] = key;
+    }
+
+  public:
+
+    /// Indicates that the map is reference map.
+    typedef True ReferenceMapTag;
+
+    /// \brief Reference to the value of the map.
+    ///
+    /// This class is similar to the \c int type. It can
+    /// be converted to \c int and it has the same operators.
+    class Reference {
+      friend class IterableIntMap;
+    private:
+      Reference(IterableIntMap& map, const Key& key)
+        : _key(key), _map(map) {}
+    public:
+
+      Reference& operator=(const Reference& value) {
+        _map.set(_key, static_cast<const int&>(value));
+         return *this;
+      }
+
+      operator const int&() const {
+        return static_cast<const IterableIntMap&>(_map)[_key];
+      }
+
+      Reference& operator=(int value) {
+        _map.set(_key, value);
+        return *this;
+      }
+      Reference& operator++() {
+        _map.set(_key, _map[_key] + 1);
+        return *this;
+      }
+      int operator++(int) {
+        int value = _map[_key];
+        _map.set(_key, value + 1);
+        return value;
+      }
+      Reference& operator--() {
+        _map.set(_key, _map[_key] - 1);
+        return *this;
+      }
+      int operator--(int) {
+        int value = _map[_key];
+        _map.set(_key, value - 1);
+        return value;
+      }
+      Reference& operator+=(int value) {
+        _map.set(_key, _map[_key] + value);
+        return *this;
+      }
+      Reference& operator-=(int value) {
+        _map.set(_key, _map[_key] - value);
+        return *this;
+      }
+      Reference& operator*=(int value) {
+        _map.set(_key, _map[_key] * value);
+        return *this;
+      }
+      Reference& operator/=(int value) {
+        _map.set(_key, _map[_key] / value);
+        return *this;
+      }
+      Reference& operator%=(int value) {
+        _map.set(_key, _map[_key] % value);
+        return *this;
+      }
+      Reference& operator&=(int value) {
+        _map.set(_key, _map[_key] & value);
+        return *this;
+      }
+      Reference& operator|=(int value) {
+        _map.set(_key, _map[_key] | value);
+        return *this;
+      }
+      Reference& operator^=(int value) {
+        _map.set(_key, _map[_key] ^ value);
+        return *this;
+      }
+      Reference& operator<<=(int value) {
+        _map.set(_key, _map[_key] << value);
+        return *this;
+      }
+      Reference& operator>>=(int value) {
+        _map.set(_key, _map[_key] >> value);
+        return *this;
+      }
+
+    private:
+      Key _key;
+      IterableIntMap& _map;
+    };
+
+    /// The const reference type.
+    typedef const Value& ConstReference;
+
+    /// \brief Gives back the maximal value plus one.
+    ///
+    /// Gives back the maximal value plus one.
+    int size() const {
+      return _first.size();
+    }
+
+    /// \brief Set operation of the map.
+    ///
+    /// Set operation of the map.
+    void set(const Key& key, const Value& value) {
+      unlace(key);
+      Parent::operator[](key).value = value;
+      lace(key);
+    }
+
+    /// \brief Const subscript operator of the map.
+    ///
+    /// Const subscript operator of the map.
+    const Value& operator[](const Key& key) const {
+      return Parent::operator[](key).value;
+    }
+
+    /// \brief Subscript operator of the map.
+    ///
+    /// Subscript operator of the map.
+    Reference operator[](const Key& key) {
+      return Reference(*this, key);
+    }
+
+    /// \brief Iterator for the keys with the same value.
+    ///
+    /// Iterator for the keys with the same value. It works
+    /// like a graph item iterator, it can be converted to
+    /// the item type of the map, incremented with \c ++ operator, and
+    /// if the iterator leaves the last valid item, it will be equal to
+    /// \c INVALID.
+    class ItemIt : public Key {
+    public:
+      typedef Key Parent;
+
+      /// \brief Invalid constructor \& conversion.
+      ///
+      /// This constructor initializes the iterator to be invalid.
+      /// \sa Invalid for more details.
+      ItemIt(Invalid) : Parent(INVALID), _map(0) {}
+
+      /// \brief Creates an iterator with a value.
+      ///
+      /// Creates an iterator with a value. It iterates on the
+      /// keys mapped to the given value.
+      /// \param map The IterableIntMap.
+      /// \param value The value.
+      ItemIt(const IterableIntMap& map, int value) : _map(&map) {
+        if (value < 0 || value >= int(_map->_first.size())) {
+          Parent::operator=(INVALID);
+        } else {
+          Parent::operator=(_map->_first[value]);
+        }
+      }
+
+      /// \brief Increment operator.
+      ///
+      /// Increment operator.
+      ItemIt& operator++() {
+        Parent::operator=(_map->IterableIntMap::Parent::
+                          operator[](static_cast<Parent&>(*this)).next);
+        return *this;
+      }
+
+    private:
+      const IterableIntMap* _map;
+    };
+
+  protected:
+
+    virtual void erase(const Key& key) {
+      unlace(key);
+      Parent::erase(key);
+    }
+
+    virtual void erase(const std::vector<Key>& keys) {
+      for (int i = 0; i < int(keys.size()); ++i) {
+        unlace(keys[i]);
+      }
+      Parent::erase(keys);
+    }
+
+    virtual void clear() {
+      _first.clear();
+      Parent::clear();
+    }
+
+  private:
+    std::vector<Key> _first;
+  };
+
+  namespace _maps_bits {
+    template <typename Item, typename Value>
+    struct IterableValueMapNode {
+      IterableValueMapNode(Value _value = Value()) : value(_value) {}
+      Item prev, next;
+      Value value;
+    };
+  }
+
+  /// \brief Dynamic iterable map for comparable values.
+  ///
+  /// This class provides a special graph map type which can store a
+  /// comparable value for graph items (\c Node, \c Arc or \c Edge).
+  /// For each value it is possible to iterate on the keys mapped to
+  /// the value (\c ItemIt), and the values of the map can be accessed
+  /// with an STL compatible forward iterator (\c ValueIt).
+  /// The map stores a linked list for each value, which contains
+  /// the items mapped to the value, and the used values are stored
+  /// in balanced binary tree (\c std::map).
+  ///
+  /// \ref IterableBoolMap and \ref IterableIntMap are similar classes
+  /// specialized for \c bool and \c int values, respectively.
+  ///
+  /// This type is not reference map, so it cannot be modified with
+  /// the subscript operator.
+  ///
+  /// \tparam GR The graph type.
+  /// \tparam K The key type of the map (\c GR::Node, \c GR::Arc or
+  /// \c GR::Edge).
+  /// \tparam V The value type of the map. It can be any comparable
+  /// value type.
+  ///
+  /// \see IterableBoolMap, IterableIntMap
+  /// \see CrossRefMap
+  template <typename GR, typename K, typename V>
+  class IterableValueMap
+    : protected ItemSetTraits<GR, K>::
+        template Map<_maps_bits::IterableValueMapNode<K, V> >::Type {
+  public:
+    typedef typename ItemSetTraits<GR, K>::
+      template Map<_maps_bits::IterableValueMapNode<K, V> >::Type Parent;
+
+    /// The key type
+    typedef K Key;
+    /// The value type
+    typedef V Value;
+    /// The graph type
+    typedef GR Graph;
+
+  public:
+
+    /// \brief Constructor of the map with a given value.
+    ///
+    /// Constructor of the map with a given value.
+    explicit IterableValueMap(const Graph& graph,
+                              const Value& value = Value())
+      : Parent(graph, _maps_bits::IterableValueMapNode<K, V>(value)) {
+      for (typename Parent::ItemIt it(*this); it != INVALID; ++it) {
+        lace(it);
+      }
+    }
+
+  protected:
+
+    void unlace(const Key& key) {
+      typename Parent::Value& node = Parent::operator[](key);
+      if (node.prev != INVALID) {
+        Parent::operator[](node.prev).next = node.next;
+      } else {
+        if (node.next != INVALID) {
+          _first[node.value] = node.next;
+        } else {
+          _first.erase(node.value);
+        }
+      }
+      if (node.next != INVALID) {
+        Parent::operator[](node.next).prev = node.prev;
+      }
+    }
+
+    void lace(const Key& key) {
+      typename Parent::Value& node = Parent::operator[](key);
+      typename std::map<Value, Key>::iterator it = _first.find(node.value);
+      if (it == _first.end()) {
+        node.prev = node.next = INVALID;
+        _first.insert(std::make_pair(node.value, key));
+      } else {
+        node.prev = INVALID;
+        node.next = it->second;
+        if (node.next != INVALID) {
+          Parent::operator[](node.next).prev = key;
+        }
+        it->second = key;
+      }
+    }
+
+  public:
+
+    /// \brief Forward iterator for values.
+    ///
+    /// This iterator is an STL compatible forward
+    /// iterator on the values of the map. The values can
+    /// be accessed in the <tt>[beginValue, endValue)</tt> range.
+    class ValueIt
+      : public std::iterator<std::forward_iterator_tag, Value> {
+      friend class IterableValueMap;
+    private:
+      ValueIt(typename std::map<Value, Key>::const_iterator _it)
+        : it(_it) {}
+    public:
+
+      /// Constructor
+      ValueIt() {}
+
+      /// \e
+      ValueIt& operator++() { ++it; return *this; }
+      /// \e
+      ValueIt operator++(int) {
+        ValueIt tmp(*this);
+        operator++();
+        return tmp;
+      }
+
+      /// \e
+      const Value& operator*() const { return it->first; }
+      /// \e
+      const Value* operator->() const { return &(it->first); }
+
+      /// \e
+      bool operator==(ValueIt jt) const { return it == jt.it; }
+      /// \e
+      bool operator!=(ValueIt jt) const { return it != jt.it; }
+
+    private:
+      typename std::map<Value, Key>::const_iterator it;
+    };
+
+    /// \brief Returns an iterator to the first value.
+    ///
+    /// Returns an STL compatible iterator to the
+    /// first value of the map. The values of the
+    /// map can be accessed in the <tt>[beginValue, endValue)</tt>
+    /// range.
+    ValueIt beginValue() const {
+      return ValueIt(_first.begin());
+    }
+
+    /// \brief Returns an iterator after the last value.
+    ///
+    /// Returns an STL compatible iterator after the
+    /// last value of the map. The values of the
+    /// map can be accessed in the <tt>[beginValue, endValue)</tt>
+    /// range.
+    ValueIt endValue() const {
+      return ValueIt(_first.end());
+    }
+
+    /// \brief Set operation of the map.
+    ///
+    /// Set operation of the map.
+    void set(const Key& key, const Value& value) {
+      unlace(key);
+      Parent::operator[](key).value = value;
+      lace(key);
+    }
+
+    /// \brief Const subscript operator of the map.
+    ///
+    /// Const subscript operator of the map.
+    const Value& operator[](const Key& key) const {
+      return Parent::operator[](key).value;
+    }
+
+    /// \brief Iterator for the keys with the same value.
+    ///
+    /// Iterator for the keys with the same value. It works
+    /// like a graph item iterator, it can be converted to
+    /// the item type of the map, incremented with \c ++ operator, and
+    /// if the iterator leaves the last valid item, it will be equal to
+    /// \c INVALID.
+    class ItemIt : public Key {
+    public:
+      typedef Key Parent;
+
+      /// \brief Invalid constructor \& conversion.
+      ///
+      /// This constructor initializes the iterator to be invalid.
+      /// \sa Invalid for more details.
+      ItemIt(Invalid) : Parent(INVALID), _map(0) {}
+
+      /// \brief Creates an iterator with a value.
+      ///
+      /// Creates an iterator with a value. It iterates on the
+      /// keys which have the given value.
+      /// \param map The IterableValueMap
+      /// \param value The value
+      ItemIt(const IterableValueMap& map, const Value& value) : _map(&map) {
+        typename std::map<Value, Key>::const_iterator it =
+          map._first.find(value);
+        if (it == map._first.end()) {
+          Parent::operator=(INVALID);
+        } else {
+          Parent::operator=(it->second);
+        }
+      }
+
+      /// \brief Increment operator.
+      ///
+      /// Increment Operator.
+      ItemIt& operator++() {
+        Parent::operator=(_map->IterableValueMap::Parent::
+                          operator[](static_cast<Parent&>(*this)).next);
+        return *this;
+      }
+
+
+    private:
+      const IterableValueMap* _map;
+    };
+
+  protected:
+
+    virtual void add(const Key& key) {
+      Parent::add(key);
+      unlace(key);
+    }
+
+    virtual void add(const std::vector<Key>& keys) {
+      Parent::add(keys);
+      for (int i = 0; i < int(keys.size()); ++i) {
+        lace(keys[i]);
+      }
+    }
+
+    virtual void erase(const Key& key) {
+      unlace(key);
+      Parent::erase(key);
+    }
+
+    virtual void erase(const std::vector<Key>& keys) {
+      for (int i = 0; i < int(keys.size()); ++i) {
+        unlace(keys[i]);
+      }
+      Parent::erase(keys);
+    }
+
+    virtual void build() {
+      Parent::build();
+      for (typename Parent::ItemIt it(*this); it != INVALID; ++it) {
+        lace(it);
+      }
+    }
+
+    virtual void clear() {
+      _first.clear();
+      Parent::clear();
+    }
+
+  private:
+    std::map<Value, Key> _first;
+  };
+
+  /// \brief Map of the source nodes of arcs in a digraph.
+  ///
+  /// SourceMap provides access for the source node of each arc in a digraph,
+  /// which is returned by the \c source() function of the digraph.
+  /// \tparam GR The digraph type.
   /// \see TargetMap
-  template <typename Digraph>
+  template <typename GR>
   class SourceMap {
   public:
 
-    typedef typename Digraph::Node Value;
-    typedef typename Digraph::Arc Key;
+    /// The key type (the \c Arc type of the digraph).
+    typedef typename GR::Arc Key;
+    /// The value type (the \c Node type of the digraph).
+    typedef typename GR::Node Value;
 
     /// \brief Constructor
     ///
-    /// Constructor
+    /// Constructor.
     /// \param digraph The digraph that the map belongs to.
-    explicit SourceMap(const Digraph& digraph) : _digraph(digraph) {}
-
-    /// \brief The subscript operator.
+    explicit SourceMap(const GR& digraph) : _graph(digraph) {}
+
+    /// \brief Returns the source node of the given arc.
     ///
-    /// The subscript operator.
-    /// \param arc The arc
-    /// \return The source of the arc
+    /// Returns the source node of the given arc.
     Value operator[](const Key& arc) const {
-      return _digraph.source(arc);
+      return _graph.source(arc);
     }
 
   private:
-    const Digraph& _digraph;
+    const GR& _graph;
   };
 
   /// \brief Returns a \c SourceMap class.
   ///
   /// This function just returns an \c SourceMap class.
   /// \relates SourceMap
-  template <typename Digraph>
-  inline SourceMap<Digraph> sourceMap(const Digraph& digraph) {
-    return SourceMap<Digraph>(digraph);
+  template <typename GR>
+  inline SourceMap<GR> sourceMap(const GR& graph) {
+    return SourceMap<GR>(graph);
   }
 
-  /// \brief Returns the target of the given arc.
+  /// \brief Map of the target nodes of arcs in a digraph.
   ///
-  /// The TargetMap gives back the target Node of the given arc.
+  /// TargetMap provides access for the target node of each arc in a digraph,
+  /// which is returned by the \c target() function of the digraph.
+  /// \tparam GR The digraph type.
   /// \see SourceMap
-  template <typename Digraph>
+  template <typename GR>
   class TargetMap {
   public:
 
-    typedef typename Digraph::Node Value;
-    typedef typename Digraph::Arc Key;
+    /// The key type (the \c Arc type of the digraph).
+    typedef typename GR::Arc Key;
+    /// The value type (the \c Node type of the digraph).
+    typedef typename GR::Node Value;
 
     /// \brief Constructor
     ///
-    /// Constructor
+    /// Constructor.
     /// \param digraph The digraph that the map belongs to.
-    explicit TargetMap(const Digraph& digraph) : _digraph(digraph) {}
-
-    /// \brief The subscript operator.
+    explicit TargetMap(const GR& digraph) : _graph(digraph) {}
+
+    /// \brief Returns the target node of the given arc.
     ///
-    /// The subscript operator.
-    /// \param e The arc
-    /// \return The target of the arc
+    /// Returns the target node of the given arc.
     Value operator[](const Key& e) const {
-      return _digraph.target(e);
+      return _graph.target(e);
     }
 
   private:
-    const Digraph& _digraph;
+    const GR& _graph;
   };
 
   /// \brief Returns a \c TargetMap class.
   ///
   /// This function just returns a \c TargetMap class.
   /// \relates TargetMap
-  template <typename Digraph>
-  inline TargetMap<Digraph> targetMap(const Digraph& digraph) {
-    return TargetMap<Digraph>(digraph);
+  template <typename GR>
+  inline TargetMap<GR> targetMap(const GR& graph) {
+    return TargetMap<GR>(graph);
   }
 
-  /// \brief Returns the "forward" directed arc view of an edge.
+  /// \brief Map of the "forward" directed arc view of edges in a graph.
   ///
-  /// Returns the "forward" directed arc view of an edge.
+  /// ForwardMap provides access for the "forward" directed arc view of
+  /// each edge in a graph, which is returned by the \c direct() function
+  /// of the graph with \c true parameter.
+  /// \tparam GR The graph type.
   /// \see BackwardMap
-  template <typename Graph>
+  template <typename GR>
   class ForwardMap {
   public:
 
-    typedef typename Graph::Arc Value;
-    typedef typename Graph::Edge Key;
+    /// The key type (the \c Edge type of the digraph).
+    typedef typename GR::Edge Key;
+    /// The value type (the \c Arc type of the digraph).
+    typedef typename GR::Arc Value;
 
     /// \brief Constructor
     ///
-    /// Constructor
+    /// Constructor.
     /// \param graph The graph that the map belongs to.
-    explicit ForwardMap(const Graph& graph) : _graph(graph) {}
-
-    /// \brief The subscript operator.
+    explicit ForwardMap(const GR& graph) : _graph(graph) {}
+
+    /// \brief Returns the "forward" directed arc view of the given edge.
     ///
-    /// The subscript operator.
-    /// \param key An edge
-    /// \return The "forward" directed arc view of edge
+    /// Returns the "forward" directed arc view of the given edge.
     Value operator[](const Key& key) const {
       return _graph.direct(key, true);
     }
 
   private:
-    const Graph& _graph;
+    const GR& _graph;
   };
 
   /// \brief Returns a \c ForwardMap class.
   ///
   /// This function just returns an \c ForwardMap class.
   /// \relates ForwardMap
-  template <typename Graph>
-  inline ForwardMap<Graph> forwardMap(const Graph& graph) {
-    return ForwardMap<Graph>(graph);
+  template <typename GR>
+  inline ForwardMap<GR> forwardMap(const GR& graph) {
+    return ForwardMap<GR>(graph);
   }
 
-  /// \brief Returns the "backward" directed arc view of an edge.
+  /// \brief Map of the "backward" directed arc view of edges in a graph.
   ///
-  /// Returns the "backward" directed arc view of an edge.
+  /// BackwardMap provides access for the "backward" directed arc view of
+  /// each edge in a graph, which is returned by the \c direct() function
+  /// of the graph with \c false parameter.
+  /// \tparam GR The graph type.
   /// \see ForwardMap
-  template <typename Graph>
+  template <typename GR>
   class BackwardMap {
   public:
 
-    typedef typename Graph::Arc Value;
-    typedef typename Graph::Edge Key;
+    /// The key type (the \c Edge type of the digraph).
+    typedef typename GR::Edge Key;
+    /// The value type (the \c Arc type of the digraph).
+    typedef typename GR::Arc Value;
 
     /// \brief Constructor
     ///
-    /// Constructor
+    /// Constructor.
     /// \param graph The graph that the map belongs to.
-    explicit BackwardMap(const Graph& graph) : _graph(graph) {}
-
-    /// \brief The subscript operator.
+    explicit BackwardMap(const GR& graph) : _graph(graph) {}
+
+    /// \brief Returns the "backward" directed arc view of the given edge.
     ///
-    /// The subscript operator.
-    /// \param key An edge
-    /// \return The "backward" directed arc view of edge
+    /// Returns the "backward" directed arc view of the given edge.
     Value operator[](const Key& key) const {
       return _graph.direct(key, false);
     }
 
   private:
-    const Graph& _graph;
+    const GR& _graph;
   };
 
   /// \brief Returns a \c BackwardMap class
 
   /// This function just returns a \c BackwardMap class.
   /// \relates BackwardMap
-  template <typename Graph>
-  inline BackwardMap<Graph> backwardMap(const Graph& graph) {
-    return BackwardMap<Graph>(graph);
+  template <typename GR>
+  inline BackwardMap<GR> backwardMap(const GR& graph) {
+    return BackwardMap<GR>(graph);
   }
 
-  /// \brief Potential difference map
-  ///
-  /// If there is an potential map on the nodes then we
-  /// can get an arc map as we get the substraction of the
-  /// values of the target and source.
-  template <typename Digraph, typename NodeMap>
-  class PotentialDifferenceMap {
-  public:
-    typedef typename Digraph::Arc Key;
-    typedef typename NodeMap::Value Value;
-
-    /// \brief Constructor
-    ///
-    /// Contructor of the map
-    explicit PotentialDifferenceMap(const Digraph& digraph,
-                                    const NodeMap& potential)
-      : _digraph(digraph), _potential(potential) {}
-
-    /// \brief Const subscription operator
-    ///
-    /// Const subscription operator
-    Value operator[](const Key& arc) const {
-      return _potential[_digraph.target(arc)] -
-        _potential[_digraph.source(arc)];
-    }
-
-  private:
-    const Digraph& _digraph;
-    const NodeMap& _potential;
-  };
-
-  /// \brief Returns a PotentialDifferenceMap.
-  ///
-  /// This function just returns a PotentialDifferenceMap.
-  /// \relates PotentialDifferenceMap
-  template <typename Digraph, typename NodeMap>
-  PotentialDifferenceMap<Digraph, NodeMap>
-  potentialDifferenceMap(const Digraph& digraph, const NodeMap& potential) {
-    return PotentialDifferenceMap<Digraph, NodeMap>(digraph, potential);
-  }
-
-  /// \brief Map of the node in-degrees.
+  /// \brief Map of the in-degrees of nodes in a digraph.
   ///
   /// This map returns the in-degree of a node. Once it is constructed,
-  /// the degrees are stored in a standard NodeMap, so each query is done
+  /// the degrees are stored in a standard \c NodeMap, so each query is done
   /// in constant time. On the other hand, the values are updated automatically
   /// whenever the digraph changes.
   ///
-  /// \warning Besides addNode() and addArc(), a digraph structure may provide
-  /// alternative ways to modify the digraph. The correct behavior of InDegMap
-  /// is not guarantied if these additional features are used. For example
-  /// the functions \ref ListDigraph::changeSource() "changeSource()",
+  /// \warning Besides \c addNode() and \c addArc(), a digraph structure
+  /// may provide alternative ways to modify the digraph.
+  /// The correct behavior of InDegMap is not guarantied if these additional
+  /// features are used. For example the functions
+  /// \ref ListDigraph::changeSource() "changeSource()",
   /// \ref ListDigraph::changeTarget() "changeTarget()" and
   /// \ref ListDigraph::reverseArc() "reverseArc()"
   /// of \ref ListDigraph will \e not update the degree values correctly.
   ///
   /// \sa OutDegMap
-
-  template <typename _Digraph>
+  template <typename GR>
   class InDegMap
-    : protected ItemSetTraits<_Digraph, typename _Digraph::Arc>
+    : protected ItemSetTraits<GR, typename GR::Arc>
       ::ItemNotifier::ObserverBase {
 
   public:
 
-    typedef _Digraph Digraph;
+    /// The graph type of InDegMap
+    typedef GR Graph;
+    typedef GR Digraph;
+    /// The key type
+    typedef typename Digraph::Node Key;
+    /// The value type
     typedef int Value;
-    typedef typename Digraph::Node Key;
 
     typedef typename ItemSetTraits<Digraph, typename Digraph::Arc>
     ::ItemNotifier::ObserverBase Parent;
@@ -2523,9 +3528,9 @@
 
     /// \brief Constructor.
     ///
-    /// Constructor for creating in-degree map.
-    explicit InDegMap(const Digraph& digraph)
-      : _digraph(digraph), _deg(digraph) {
+    /// Constructor for creating an in-degree map.
+    explicit InDegMap(const Digraph& graph)
+      : _digraph(graph), _deg(graph) {
       Parent::attach(_digraph.notifier(typename Digraph::Arc()));
 
       for(typename Digraph::NodeIt it(_digraph); it != INVALID; ++it) {
@@ -2533,6 +3538,8 @@
       }
     }
 
+    /// \brief Gives back the in-degree of a Node.
+    ///
     /// Gives back the in-degree of a Node.
     int operator[](const Key& key) const {
       return _deg[key];
@@ -2579,33 +3586,37 @@
     AutoNodeMap _deg;
   };
 
-  /// \brief Map of the node out-degrees.
+  /// \brief Map of the out-degrees of nodes in a digraph.
   ///
   /// This map returns the out-degree of a node. Once it is constructed,
-  /// the degrees are stored in a standard NodeMap, so each query is done
+  /// the degrees are stored in a standard \c NodeMap, so each query is done
   /// in constant time. On the other hand, the values are updated automatically
   /// whenever the digraph changes.
   ///
-  /// \warning Besides addNode() and addArc(), a digraph structure may provide
-  /// alternative ways to modify the digraph. The correct behavior of OutDegMap
-  /// is not guarantied if these additional features are used. For example
-  /// the functions \ref ListDigraph::changeSource() "changeSource()",
+  /// \warning Besides \c addNode() and \c addArc(), a digraph structure
+  /// may provide alternative ways to modify the digraph.
+  /// The correct behavior of OutDegMap is not guarantied if these additional
+  /// features are used. For example the functions
+  /// \ref ListDigraph::changeSource() "changeSource()",
   /// \ref ListDigraph::changeTarget() "changeTarget()" and
   /// \ref ListDigraph::reverseArc() "reverseArc()"
   /// of \ref ListDigraph will \e not update the degree values correctly.
   ///
   /// \sa InDegMap
-
-  template <typename _Digraph>
+  template <typename GR>
   class OutDegMap
-    : protected ItemSetTraits<_Digraph, typename _Digraph::Arc>
+    : protected ItemSetTraits<GR, typename GR::Arc>
       ::ItemNotifier::ObserverBase {
 
   public:
 
-    typedef _Digraph Digraph;
+    /// The graph type of OutDegMap
+    typedef GR Graph;
+    typedef GR Digraph;
+    /// The key type
+    typedef typename Digraph::Node Key;
+    /// The value type
     typedef int Value;
-    typedef typename Digraph::Node Key;
 
     typedef typename ItemSetTraits<Digraph, typename Digraph::Arc>
     ::ItemNotifier::ObserverBase Parent;
@@ -2645,9 +3656,9 @@
 
     /// \brief Constructor.
     ///
-    /// Constructor for creating out-degree map.
-    explicit OutDegMap(const Digraph& digraph)
-      : _digraph(digraph), _deg(digraph) {
+    /// Constructor for creating an out-degree map.
+    explicit OutDegMap(const Digraph& graph)
+      : _digraph(graph), _deg(graph) {
       Parent::attach(_digraph.notifier(typename Digraph::Arc()));
 
       for(typename Digraph::NodeIt it(_digraph); it != INVALID; ++it) {
@@ -2655,6 +3666,8 @@
       }
     }
 
+    /// \brief Gives back the out-degree of a Node.
+    ///
     /// Gives back the out-degree of a Node.
     int operator[](const Key& key) const {
       return _deg[key];
@@ -2701,6 +3714,56 @@
     AutoNodeMap _deg;
   };
 
+  /// \brief Potential difference map
+  ///
+  /// PotentialDifferenceMap returns the difference between the potentials of
+  /// the source and target nodes of each arc in a digraph, i.e. it returns
+  /// \code
+  ///   potential[gr.target(arc)] - potential[gr.source(arc)].
+  /// \endcode
+  /// \tparam GR The digraph type.
+  /// \tparam POT A node map storing the potentials.
+  template <typename GR, typename POT>
+  class PotentialDifferenceMap {
+  public:
+    /// Key type
+    typedef typename GR::Arc Key;
+    /// Value type
+    typedef typename POT::Value Value;
+
+    /// \brief Constructor
+    ///
+    /// Contructor of the map.
+    explicit PotentialDifferenceMap(const GR& gr,
+                                    const POT& potential)
+      : _digraph(gr), _potential(potential) {}
+
+    /// \brief Returns the potential difference for the given arc.
+    ///
+    /// Returns the potential difference for the given arc, i.e.
+    /// \code
+    ///   potential[gr.target(arc)] - potential[gr.source(arc)].
+    /// \endcode
+    Value operator[](const Key& arc) const {
+      return _potential[_digraph.target(arc)] -
+        _potential[_digraph.source(arc)];
+    }
+
+  private:
+    const GR& _digraph;
+    const POT& _potential;
+  };
+
+  /// \brief Returns a PotentialDifferenceMap.
+  ///
+  /// This function just returns a PotentialDifferenceMap.
+  /// \relates PotentialDifferenceMap
+  template <typename GR, typename POT>
+  PotentialDifferenceMap<GR, POT>
+  potentialDifferenceMap(const GR& gr, const POT& potential) {
+    return PotentialDifferenceMap<GR, POT>(gr, potential);
+  }
+
   /// @}
 }