diff --git a/lemon/concepts/maps.h b/lemon/concepts/maps.h
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+/* -*- C++ -*-
+ *
+ * This file is a part of LEMON, a generic C++ optimization library
+ *
+ * Copyright (C) 2003-2007
+ * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
+ * (Egervary Research Group on Combinatorial Optimization, EGRES).
+ *
+ * Permission to use, modify and distribute this software is granted
+ * provided that this copyright notice appears in all copies. For
+ * precise terms see the accompanying LICENSE file.
+ *
+ * This software is provided "AS IS" with no warranty of any kind,
+ * express or implied, and with no claim as to its suitability for any
+ * purpose.
+ *
+ */
+
+#ifndef LEMON_CONCEPT_MAPS_H
+#define LEMON_CONCEPT_MAPS_H
+
+#include <lemon/bits/utility.h>
+#include <lemon/concept_check.h>
+
+///\ingroup concept
+///\file
+///\brief Map concepts checking classes for testing and documenting.
+
+namespace lemon {
+
+  namespace concepts {
+  
+    /// \addtogroup concept
+    /// @{
+
+    /// Readable map concept
+    template<typename K, typename T>
+    class ReadMap
+    {
+    public:
+      /// Map's key type.
+      typedef K Key;    
+      /// Map's value type. (The type of objects associated with the keys).
+      typedef T Value;
+
+      /// Returns the value associated with a key.
+
+      /// \bug Value should n't need to be default constructible.
+      ///
+      Value operator[](const Key &) const {return Value();}
+
+      template<typename _ReadMap>
+      struct Constraints {
+
+	void constraints() {
+	  Value val = m[key];
+	  val = m[key];
+	  typename _ReadMap::Value own_val = m[own_key]; 
+	  own_val = m[own_key]; 
+
+	  ignore_unused_variable_warning(val);
+	  ignore_unused_variable_warning(own_val);
+	  ignore_unused_variable_warning(key);
+	}
+	Key& key;
+	typename _ReadMap::Key& own_key;
+	_ReadMap& m;
+      };
+      
+    };
+
+
+    /// Writable map concept
+    template<typename K, typename T>
+    class WriteMap
+    {
+    public:
+      /// Map's key type.
+      typedef K Key;    
+      /// Map's value type. (The type of objects associated with the keys).
+      typedef T Value;
+
+      /// Sets the value associated with a key.
+      void set(const Key &,const Value &) {}
+
+      ///Default constructor
+      WriteMap() {}
+
+      template <typename _WriteMap>
+      struct Constraints {
+	void constraints() {
+	  // No constraints for constructor.
+	  m.set(key, val);
+	  m.set(own_key, own_val);
+	  ignore_unused_variable_warning(key);
+	  ignore_unused_variable_warning(val);
+	  ignore_unused_variable_warning(own_key);
+	  ignore_unused_variable_warning(own_val);
+	}
+
+	Value& val;
+	typename _WriteMap::Value own_val;
+	Key& key;
+	typename _WriteMap::Key& own_key;
+	_WriteMap& m;
+
+      };
+    };
+
+    ///Read/Writable map concept
+    template<typename K, typename T>
+    class ReadWriteMap : public ReadMap<K,T>,
+			    public WriteMap<K,T>
+    {
+    public:
+      /// Map's key type.
+      typedef K Key;    
+      /// Map's value type. (The type of objects associated with the keys).
+      typedef T Value;
+
+      /// Returns the value associated with a key.
+      Value operator[](const Key &) const {return Value();}
+      /// Sets the value associated with a key.
+      void set(const Key & ,const Value &) {}
+
+      template<typename _ReadWriteMap>
+      struct Constraints {
+	void constraints() {
+	  checkConcept<ReadMap<K, T>, _ReadWriteMap >();
+	  checkConcept<WriteMap<K, T>, _ReadWriteMap >();
+	}
+      };
+    };
+  
+  
+    ///Dereferable map concept
+    template<typename K, typename T, typename R, typename CR>
+    class ReferenceMap : public ReadWriteMap<K,T>
+    {
+    public:
+      /// Tag for reference maps.
+      typedef True ReferenceMapTag;
+      /// Map's key type.
+      typedef K Key;    
+      /// Map's value type. (The type of objects associated with the keys).
+      typedef T Value;
+      /// Map's reference type.
+      typedef R Reference;
+      /// Map's const reference type.
+      typedef CR ConstReference;
+
+    protected:
+      Value tmp;
+    public:
+
+      ///Returns a reference to the value associated to a key.
+      Reference operator[](const Key &) { return tmp; }
+      ///Returns a const reference to the value associated to a key.
+      ConstReference operator[](const Key &) const
+      { return tmp; }
+      /// Sets the value associated with a key.
+      void set(const Key &k,const Value &t) { operator[](k)=t; }
+
+      // \todo rethink this concept
+      template<typename _ReferenceMap>
+      struct ReferenceMapConcept {
+
+	void constraints() {
+	  checkConcept<ReadWriteMap, _ReferenceMap >();
+	  m[key] = val;
+	  val  = m[key];
+	  m[key] = ref;
+	  ref = m[key];
+	  m[own_key] = own_val;
+	  own_val  = m[own_key];
+	  m[own_key] = own_ref;
+	  own_ref = m[own_key];	  	  
+	}
+
+	typename _ReferenceMap::Key& own_key;
+	typename _ReferenceMap::Value& own_val;
+	typename _ReferenceMap::Reference& own_ref;
+	Key& key;
+	Value& val;
+	Reference& ref;
+	_ReferenceMap& m;
+      };
+    };
+
+    // @}
+
+  } //namespace concepts
+} //namespace lemon
+#endif // LEMON_CONCEPT_MAPS_H