diff --git a/lemon/bits/alteration_notifier.h b/lemon/bits/alteration_notifier.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_BITS_ALTERATION_NOTIFIER_H
+#define LEMON_BITS_ALTERATION_NOTIFIER_H
+
+#include <vector>
+#include <list>
+
+#include <lemon/bits/utility.h>
+
+///\ingroup graphbits
+///\file
+///\brief Observer notifier for graph alteration observers.
+
+namespace lemon {
+
+  /// \ingroup graphbits
+  ///
+  /// \brief Notifier class to notify observes about alterations in 
+  /// a container.
+  ///
+  /// The simple graph's can be refered as two containers, one node container
+  /// and one edge container. But they are not standard containers they
+  /// does not store values directly they are just key continars for more
+  /// value containers which are the node and edge maps.
+  ///
+  /// The graph's node and edge sets can be changed as we add or erase
+  /// nodes and edges in the graph. Lemon would like to handle easily
+  /// that the node and edge maps should contain values for all nodes or
+  /// edges. If we want to check on every indicing if the map contains
+  /// the current indicing key that cause a drawback in the performance
+  /// in the library. We use another solution we notify all maps about
+  /// an alteration in the graph, which cause only drawback on the
+  /// alteration of the graph.
+  ///
+  /// This class provides an interface to the container. The \e first() and \e 
+  /// next() member functions make possible to iterate on the keys of the
+  /// container. The \e id() function returns an integer id for each key.
+  /// The \e maxId() function gives back an upper bound of the ids.
+  ///
+  /// For the proper functonality of this class, we should notify it
+  /// about each alteration in the container. The alterations have four type
+  /// as \e add(), \e erase(), \e build() and \e clear(). The \e add() and
+  /// \e erase() signals that only one or few items added or erased to or
+  /// from the graph. If all items are erased from the graph or from an empty
+  /// graph a new graph is builded then it can be signaled with the
+  /// clear() and build() members. Important rule that if we erase items 
+  /// from graph we should first signal the alteration and after that erase
+  /// them from the container, on the other way on item addition we should
+  /// first extend the container and just after that signal the alteration.
+  ///
+  /// The alteration can be observed with a class inherited from the
+  /// \e ObserverBase nested class. The signals can be handled with
+  /// overriding the virtual functions defined in the base class.  The
+  /// observer base can be attached to the notifier with the 
+  /// \e attach() member and can be detached with detach() function. The
+  /// alteration handlers should not call any function which signals
+  /// an other alteration in the same notifier and should not
+  /// detach any observer from the notifier.
+  ///
+  /// Alteration observers try to be exception safe. If an \e add() or
+  /// a \e clear() function throws an exception then the remaining
+  /// observeres will not be notified and the fulfilled additions will
+  /// be rolled back by calling the \e erase() or \e clear()
+  /// functions. Thence the \e erase() and \e clear() should not throw
+  /// exception. Actullay, it can be throw only 
+  /// \ref AlterationObserver::ImmediateDetach ImmediateDetach
+  /// exception which detach the observer from the notifier.
+  ///
+  /// There are some place when the alteration observing is not completly
+  /// reliable. If we want to carry out the node degree in the graph
+  /// as in the \ref InDegMap and we use the reverseEdge that cause 
+  /// unreliable functionality. Because the alteration observing signals
+  /// only erasing and adding but not the reversing it will stores bad
+  /// degrees. The sub graph adaptors cannot signal the alterations because
+  /// just a setting in the filter map can modify the graph and this cannot
+  /// be watched in any way.
+  ///
+  /// \param _Container The container which is observed.
+  /// \param _Item The item type which is obserbved.
+  ///
+  /// \author Balazs Dezso
+
+  template <typename _Container, typename _Item>
+  class AlterationNotifier {
+  public:
+
+    typedef True Notifier;
+
+    typedef _Container Container;
+    typedef _Item Item;
+
+    /// \brief Exception which can be called from \e clear() and 
+    /// \e erase().
+    ///
+    /// From the \e clear() and \e erase() function only this
+    /// exception is allowed to throw. The exception immediatly
+    /// detaches the current observer from the notifier. Because the
+    /// \e clear() and \e erase() should not throw other exceptions
+    /// it can be used to invalidate the observer.
+    struct ImmediateDetach {};
+
+    /// \brief ObserverBase is the base class for the observers.
+    ///
+    /// ObserverBase is the abstract base class for the observers.
+    /// It will be notified about an item was inserted into or
+    /// erased from the graph.
+    ///
+    /// The observer interface contains some pure virtual functions
+    /// to override. The add() and erase() functions are
+    /// to notify the oberver when one item is added or
+    /// erased.
+    ///
+    /// The build() and clear() members are to notify the observer
+    /// about the container is built from an empty container or
+    /// is cleared to an empty container. 
+    /// 
+    /// \author Balazs Dezso
+
+    class ObserverBase {
+    protected:
+      typedef AlterationNotifier Notifier;
+
+      friend class AlterationNotifier;
+
+      /// \brief Default constructor.
+      ///
+      /// Default constructor for ObserverBase.
+      /// 
+      ObserverBase() : _notifier(0) {}
+
+      /// \brief Constructor which attach the observer into notifier.
+      ///
+      /// Constructor which attach the observer into notifier.
+      ObserverBase(AlterationNotifier& nf) {
+        attach(nf);
+      }
+
+      /// \brief Constructor which attach the obserever to the same notifier.
+      ///
+      /// Constructor which attach the obserever to the same notifier as
+      /// the other observer is attached to. 
+      ObserverBase(const ObserverBase& copy) {
+	if (copy.attached()) {
+          attach(*copy.notifier());
+	}
+      }
+	
+      /// \brief Destructor
+      virtual ~ObserverBase() {
+        if (attached()) {
+          detach();
+        }
+      }
+
+      /// \brief Attaches the observer into an AlterationNotifier.
+      ///
+      /// This member attaches the observer into an AlterationNotifier.
+      ///
+      void attach(AlterationNotifier& nf) {
+	nf.attach(*this);
+      }
+      
+      /// \brief Detaches the observer into an AlterationNotifier.
+      ///
+      /// This member detaches the observer from an AlterationNotifier.
+      ///
+      void detach() {
+        _notifier->detach(*this);
+      }
+      
+      /// \brief Gives back a pointer to the notifier which the map 
+      /// attached into.
+      ///
+      /// This function gives back a pointer to the notifier which the map
+      /// attached into.
+      ///
+      Notifier* notifier() const { return const_cast<Notifier*>(_notifier); }
+      
+      /// Gives back true when the observer is attached into a notifier.
+      bool attached() const { return _notifier != 0; }
+
+    private:
+
+      ObserverBase& operator=(const ObserverBase& copy);
+
+    protected:
+      
+      Notifier* _notifier;
+      typename std::list<ObserverBase*>::iterator _index;
+
+      /// \brief The member function to notificate the observer about an
+      /// item is added to the container.
+      ///
+      /// The add() member function notificates the observer about an item
+      /// is added to the container. It have to be overrided in the
+      /// subclasses.
+      virtual void add(const Item&) = 0;
+
+      /// \brief The member function to notificate the observer about 
+      /// more item is added to the container.
+      ///
+      /// The add() member function notificates the observer about more item
+      /// is added to the container. It have to be overrided in the
+      /// subclasses.
+      virtual void add(const std::vector<Item>& items) = 0;
+
+      /// \brief The member function to notificate the observer about an
+      /// item is erased from the container.
+      ///
+      /// The erase() member function notificates the observer about an
+      /// item is erased from the container. It have to be overrided in
+      /// the subclasses.	
+      virtual void erase(const Item&) = 0;
+
+      /// \brief The member function to notificate the observer about 
+      /// more item is erased from the container.
+      ///
+      /// The erase() member function notificates the observer about more item
+      /// is erased from the container. It have to be overrided in the
+      /// subclasses.
+      virtual void erase(const std::vector<Item>& items) = 0;
+
+      /// \brief The member function to notificate the observer about the
+      /// container is built.
+      ///
+      /// The build() member function notificates the observer about the
+      /// container is built from an empty container. It have to be
+      /// overrided in the subclasses.
+
+      virtual void build() = 0;
+
+      /// \brief The member function to notificate the observer about all
+      /// items are erased from the container.
+      ///
+      /// The clear() member function notificates the observer about all
+      /// items are erased from the container. It have to be overrided in
+      /// the subclasses.      
+      virtual void clear() = 0;
+
+    };
+	
+  protected:
+
+    const Container* container;
+
+    typedef std::list<ObserverBase*> Observers; 
+    Observers _observers;
+
+		
+  public:
+
+    /// \brief Default constructor.
+    ///
+    /// The default constructor of the AlterationNotifier. 
+    /// It creates an empty notifier.
+    AlterationNotifier() 
+      : container(0) {}
+
+    /// \brief Constructor.
+    ///
+    /// Constructor with the observed container parameter.
+    AlterationNotifier(const Container& _container) 
+      : container(&_container) {}
+
+    /// \brief Copy Constructor of the AlterationNotifier. 
+    ///
+    /// Copy constructor of the AlterationNotifier. 
+    /// It creates only an empty notifier because the copiable
+    /// notifier's observers have to be registered still into that notifier.
+    AlterationNotifier(const AlterationNotifier& _notifier) 
+      : container(_notifier.container) {}
+
+    /// \brief Destructor.
+    ///		
+    /// Destructor of the AlterationNotifier.
+    ///
+    ~AlterationNotifier() {
+      typename Observers::iterator it;
+      for (it = _observers.begin(); it != _observers.end(); ++it) {
+	(*it)->_notifier = 0;
+      }
+    }
+
+    /// \brief Sets the container.
+    ///
+    /// Sets the container.
+    void setContainer(const Container& _container) {
+      container = &_container;
+    }
+
+  protected:
+
+    AlterationNotifier& operator=(const AlterationNotifier&);
+
+  public:
+
+
+
+    /// \brief First item in the container.
+    ///
+    /// Returns the first item in the container. It is
+    /// for start the iteration on the container.
+    void first(Item& item) const {
+      container->first(item);
+    }
+
+    /// \brief Next item in the container.
+    ///
+    /// Returns the next item in the container. It is
+    /// for iterate on the container.
+    void next(Item& item) const {
+      container->next(item);
+    }
+
+    /// \brief Returns the id of the item.
+    ///
+    /// Returns the id of the item provided by the container.
+    int id(const Item& item) const {
+      return container->id(item);
+    }
+
+    /// \brief Returns the maximum id of the container.
+    ///
+    /// Returns the maximum id of the container.
+    int maxId() const {
+      return container->maxId(Item());
+    }
+		
+  protected:
+
+    void attach(ObserverBase& observer) {
+      observer._index = _observers.insert(_observers.begin(), &observer);
+      observer._notifier = this;
+    } 
+
+    void detach(ObserverBase& observer) {
+      _observers.erase(observer._index);
+      observer._index = _observers.end();
+      observer._notifier = 0;
+    }
+
+  public:
+	
+    /// \brief Notifies all the registed observers about an item added to 
+    /// the container.
+    ///
+    /// It notifies all the registed observers about an item added to 
+    /// the container.
+    /// 
+    void add(const Item& item) {
+      typename Observers::reverse_iterator it;
+      try {
+        for (it = _observers.rbegin(); it != _observers.rend(); ++it) {
+          (*it)->add(item);
+        }
+      } catch (...) {
+        typename Observers::iterator jt;
+        for (jt = it.base(); jt != _observers.end(); ++jt) {
+          (*jt)->erase(item);
+        }
+        throw;
+      }
+    }	
+
+    /// \brief Notifies all the registed observers about more item added to 
+    /// the container.
+    ///
+    /// It notifies all the registed observers about more item added to 
+    /// the container.
+    /// 
+    void add(const std::vector<Item>& items) {
+      typename Observers::reverse_iterator it;
+      try {
+        for (it = _observers.rbegin(); it != _observers.rend(); ++it) {
+          (*it)->add(items);
+        }
+      } catch (...) {
+        typename Observers::iterator jt;
+        for (jt = it.base(); jt != _observers.end(); ++jt) {
+          (*jt)->erase(items);
+        }
+        throw;
+      }
+    }	
+
+    /// \brief Notifies all the registed observers about an item erased from 
+    /// the container.
+    ///	
+    /// It notifies all the registed observers about an item erased from 
+    /// the container.
+    /// 
+    void erase(const Item& item) throw() {
+      typename Observers::iterator it = _observers.begin();
+      while (it != _observers.end()) {
+        try {
+          (*it)->erase(item);
+          ++it;
+        } catch (const ImmediateDetach&) {
+          it = _observers.erase(it);
+          (*it)->_index = _observers.end();
+          (*it)->_notifier = 0;
+        }
+      }
+    }
+
+    /// \brief Notifies all the registed observers about more item erased  
+    /// from the container.
+    ///	
+    /// It notifies all the registed observers about more item erased from 
+    /// the container.
+    /// 
+    void erase(const std::vector<Item>& items) {
+      typename Observers::iterator it = _observers.begin();
+      while (it != _observers.end()) {
+        try {
+          (*it)->erase(items);
+          ++it;
+        } catch (const ImmediateDetach&) {
+          it = _observers.erase(it);
+          (*it)->_index = _observers.end();
+          (*it)->_notifier = 0;
+        }
+      }
+    }
+
+    /// \brief Notifies all the registed observers about the container is 
+    /// built.
+    ///		
+    /// Notifies all the registed observers about the container is built
+    /// from an empty container.
+    void build() {
+      typename Observers::reverse_iterator it;
+      try {
+        for (it = _observers.rbegin(); it != _observers.rend(); ++it) {
+          (*it)->build();
+        }
+      } catch (...) {
+        typename Observers::iterator jt;
+        for (jt = it.base(); jt != _observers.end(); ++jt) {
+          (*jt)->clear();
+        }
+        throw;
+      }
+    }
+
+    /// \brief Notifies all the registed observers about all items are 
+    /// erased.
+    ///
+    /// Notifies all the registed observers about all items are erased
+    /// from the container.
+    void clear() {
+      typename Observers::iterator it = _observers.begin();
+      while (it != _observers.end()) {
+        try {
+          (*it)->clear();
+          ++it;
+        } catch (const ImmediateDetach&) {
+          it = _observers.erase(it);
+          (*it)->_index = _observers.end();
+          (*it)->_notifier = 0;
+        }
+      }
+    }
+  };
+
+}
+
+#endif