Index: lemon/maps.h
===================================================================
--- lemon/maps.h	(revision 741)
+++ lemon/maps.h	(revision 768)
@@ -1826,5 +1826,5 @@
   /// 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.
+  /// class \c InverseMap or with the \c operator()() member.
   ///
   /// \tparam GR The graph type.
@@ -1902,12 +1902,11 @@
 
   /// This class provides simple invertable graph maps.
-  /// It wraps an arbitrary \ref concepts::ReadWriteMap "ReadWriteMap"
-  /// and if a key is set to a new value then store it
-  /// in the inverse map.
+  /// 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 values of the map can be accessed
   /// with stl compatible forward iterator.
   ///
   /// This type is not reference map, so it cannot be modified with
-  /// the subscription operator.
+  /// the subscript operator.
   ///
   /// \tparam GR The graph type.
@@ -1925,5 +1924,5 @@
       template Map<V>::Type Map;
 
-    typedef std::map<V, K> Container;
+    typedef std::multimap<V, K> Container;
     Container _inv_map;
 
@@ -1950,4 +1949,6 @@
     /// iterator on the values of the map. The values can
     /// 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 ValueIterator
       : public std::iterator<std::forward_iterator_tag, Value> {
@@ -2002,7 +2003,11 @@
     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(std::make_pair(val, key));
@@ -2018,10 +2023,21 @@
     }
 
-    /// \brief Gives back the 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);
+    /// \brief Gives back an item by its value.
+    ///
+    /// 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);
     }
 
@@ -2034,7 +2050,11 @@
     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);
@@ -2048,7 +2068,11 @@
       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;
+          }
         }
       }
@@ -2086,6 +2110,7 @@
       /// \brief Subscript operator.
       ///
-      /// Subscript operator. It gives back the item
-      /// that was last assigned to the given 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);
@@ -2105,9 +2130,9 @@
   };
 
-  /// \brief Provides continuous and unique ID for the
+  /// \brief Provides continuous and unique id for the
   /// items of a graph.
   ///
   /// RangeIdMap provides a unique and continuous
-  /// ID for each item of a given type (\c Node, \c Arc or
+  /// 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,
@@ -2120,5 +2145,5 @@
   /// 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.
+  /// or with the \c operator()() member.
   ///
   /// \tparam GR The graph type.
Index: test/maps_test.cc
===================================================================
--- test/maps_test.cc	(revision 741)
+++ test/maps_test.cc	(revision 768)
@@ -23,4 +23,5 @@
 #include <lemon/concepts/maps.h>
 #include <lemon/maps.h>
+#include <lemon/list_graph.h>
 #include <lemon/smart_graph.h>
 
@@ -330,4 +331,8 @@
   {
     typedef std::vector<int> vec;
+    checkConcept<WriteMap<int, bool>, LoggerBoolMap<vec::iterator> >();
+    checkConcept<WriteMap<int, bool>,
+                 LoggerBoolMap<std::back_insert_iterator<vec> > >();
+
     vec v1;
     vec v2(10);
@@ -350,4 +355,144 @@
       check(v1[i++] == *it, "Something is wrong with LoggerBoolMap");
   }
+  
+  // IdMap, RangeIdMap
+  {
+    typedef ListDigraph Graph;
+    DIGRAPH_TYPEDEFS(Graph);
+
+    checkConcept<ReadMap<Node, int>, IdMap<Graph, Node> >();
+    checkConcept<ReadMap<Arc, int>, IdMap<Graph, Arc> >();
+    checkConcept<ReadMap<Node, int>, RangeIdMap<Graph, Node> >();
+    checkConcept<ReadMap<Arc, int>, RangeIdMap<Graph, Arc> >();
+    
+    Graph gr;
+    IdMap<Graph, Node> nmap(gr);
+    IdMap<Graph, Arc> amap(gr);
+    RangeIdMap<Graph, Node> nrmap(gr);
+    RangeIdMap<Graph, Arc> armap(gr);
+    
+    Node n0 = gr.addNode();
+    Node n1 = gr.addNode();
+    Node n2 = gr.addNode();
+    
+    Arc a0 = gr.addArc(n0, n1);
+    Arc a1 = gr.addArc(n0, n2);
+    Arc a2 = gr.addArc(n2, n1);
+    Arc a3 = gr.addArc(n2, n0);
+    
+    check(nmap[n0] == gr.id(n0) && nmap(gr.id(n0)) == n0, "Wrong IdMap");
+    check(nmap[n1] == gr.id(n1) && nmap(gr.id(n1)) == n1, "Wrong IdMap");
+    check(nmap[n2] == gr.id(n2) && nmap(gr.id(n2)) == n2, "Wrong IdMap");
+
+    check(amap[a0] == gr.id(a0) && amap(gr.id(a0)) == a0, "Wrong IdMap");
+    check(amap[a1] == gr.id(a1) && amap(gr.id(a1)) == a1, "Wrong IdMap");
+    check(amap[a2] == gr.id(a2) && amap(gr.id(a2)) == a2, "Wrong IdMap");
+    check(amap[a3] == gr.id(a3) && amap(gr.id(a3)) == a3, "Wrong IdMap");
+
+    check(nmap.inverse()[gr.id(n0)] == n0, "Wrong IdMap::InverseMap");
+    check(amap.inverse()[gr.id(a0)] == a0, "Wrong IdMap::InverseMap");
+    
+    check(nrmap.size() == 3 && armap.size() == 4,
+          "Wrong RangeIdMap::size()");
+
+    check(nrmap[n0] == 0 && nrmap(0) == n0, "Wrong RangeIdMap");
+    check(nrmap[n1] == 1 && nrmap(1) == n1, "Wrong RangeIdMap");
+    check(nrmap[n2] == 2 && nrmap(2) == n2, "Wrong RangeIdMap");
+    
+    check(armap[a0] == 0 && armap(0) == a0, "Wrong RangeIdMap");
+    check(armap[a1] == 1 && armap(1) == a1, "Wrong RangeIdMap");
+    check(armap[a2] == 2 && armap(2) == a2, "Wrong RangeIdMap");
+    check(armap[a3] == 3 && armap(3) == a3, "Wrong RangeIdMap");
+
+    check(nrmap.inverse()[0] == n0, "Wrong RangeIdMap::InverseMap");
+    check(armap.inverse()[0] == a0, "Wrong RangeIdMap::InverseMap");
+    
+    gr.erase(n1);
+    
+    if (nrmap[n0] == 1) nrmap.swap(n0, n2);
+    nrmap.swap(n2, n0);
+    if (armap[a1] == 1) armap.swap(a1, a3);
+    armap.swap(a3, a1);
+    
+    check(nrmap.size() == 2 && armap.size() == 2,
+          "Wrong RangeIdMap::size()");
+
+    check(nrmap[n0] == 1 && nrmap(1) == n0, "Wrong RangeIdMap");
+    check(nrmap[n2] == 0 && nrmap(0) == n2, "Wrong RangeIdMap");
+    
+    check(armap[a1] == 1 && armap(1) == a1, "Wrong RangeIdMap");
+    check(armap[a3] == 0 && armap(0) == a3, "Wrong RangeIdMap");
+
+    check(nrmap.inverse()[0] == n2, "Wrong RangeIdMap::InverseMap");
+    check(armap.inverse()[0] == a3, "Wrong RangeIdMap::InverseMap");
+  }
+  
+  // CrossRefMap
+  {
+    typedef ListDigraph Graph;
+    DIGRAPH_TYPEDEFS(Graph);
+
+    checkConcept<ReadWriteMap<Node, int>,
+                 CrossRefMap<Graph, Node, int> >();
+    checkConcept<ReadWriteMap<Node, bool>,
+                 CrossRefMap<Graph, Node, bool> >();
+    checkConcept<ReadWriteMap<Node, double>,
+                 CrossRefMap<Graph, Node, double> >();
+    
+    Graph gr;
+    typedef CrossRefMap<Graph, Node, char> CRMap;
+    typedef CRMap::ValueIterator ValueIt;
+    CRMap map(gr);
+    
+    Node n0 = gr.addNode();
+    Node n1 = gr.addNode();
+    Node n2 = gr.addNode();
+    
+    map.set(n0, 'A');
+    map.set(n1, 'B');
+    map.set(n2, 'C');
+    
+    check(map[n0] == 'A' && map('A') == n0 && map.inverse()['A'] == n0,
+          "Wrong CrossRefMap");
+    check(map[n1] == 'B' && map('B') == n1 && map.inverse()['B'] == n1,
+          "Wrong CrossRefMap");
+    check(map[n2] == 'C' && map('C') == n2 && map.inverse()['C'] == n2,
+          "Wrong CrossRefMap");
+    check(map.count('A') == 1 && map.count('B') == 1 && map.count('C') == 1,
+          "Wrong CrossRefMap::count()");
+    
+    ValueIt it = map.beginValue();
+    check(*it++ == 'A' && *it++ == 'B' && *it++ == 'C' &&
+          it == map.endValue(), "Wrong value iterator");
+    
+    map.set(n2, 'A');
+
+    check(map[n0] == 'A' && map[n1] == 'B' && map[n2] == 'A',
+          "Wrong CrossRefMap");
+    check(map('A') == n0 && map.inverse()['A'] == n0, "Wrong CrossRefMap");
+    check(map('B') == n1 && map.inverse()['B'] == n1, "Wrong CrossRefMap");
+    check(map('C') == INVALID && map.inverse()['C'] == INVALID,
+          "Wrong CrossRefMap");
+    check(map.count('A') == 2 && map.count('B') == 1 && map.count('C') == 0,
+          "Wrong CrossRefMap::count()");
+
+    it = map.beginValue();
+    check(*it++ == 'A' && *it++ == 'A' && *it++ == 'B' &&
+          it == map.endValue(), "Wrong value iterator");
+
+    map.set(n0, 'C');
+
+    check(map[n0] == 'C' && map[n1] == 'B' && map[n2] == 'A',
+          "Wrong CrossRefMap");
+    check(map('A') == n2 && map.inverse()['A'] == n2, "Wrong CrossRefMap");
+    check(map('B') == n1 && map.inverse()['B'] == n1, "Wrong CrossRefMap");
+    check(map('C') == n0 && map.inverse()['C'] == n0, "Wrong CrossRefMap");
+    check(map.count('A') == 1 && map.count('B') == 1 && map.count('C') == 1,
+          "Wrong CrossRefMap::count()");
+
+    it = map.beginValue();
+    check(*it++ == 'A' && *it++ == 'B' && *it++ == 'C' &&
+          it == map.endValue(), "Wrong value iterator");
+  }
 
   // Iterable bool map
