lemon/bits/alteration_notifier.h
author Alpar Juttner <alpar@cs.elte.hu>
Fri, 12 Feb 2010 22:24:26 +0100
changeset 831 cc9e0c15d747
parent 361 f58410582b9b
child 979 43a91b33f374
permissions -rw-r--r--
Merge
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/* -*- mode: C++; indent-tabs-mode: nil; -*-
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 *
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 * This file is a part of LEMON, a generic C++ optimization library.
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 *
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 * Copyright (C) 2003-2009
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 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
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 * (Egervary Research Group on Combinatorial Optimization, EGRES).
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 *
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 * Permission to use, modify and distribute this software is granted
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 * provided that this copyright notice appears in all copies. For
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 * precise terms see the accompanying LICENSE file.
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 *
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 * This software is provided "AS IS" with no warranty of any kind,
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 * express or implied, and with no claim as to its suitability for any
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 * purpose.
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 *
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 */
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#ifndef LEMON_BITS_ALTERATION_NOTIFIER_H
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#define LEMON_BITS_ALTERATION_NOTIFIER_H
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#include <vector>
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#include <list>
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#include <lemon/core.h>
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//\ingroup graphbits
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//\file
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//\brief Observer notifier for graph alteration observers.
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namespace lemon {
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  // \ingroup graphbits
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  //
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  // \brief Notifier class to notify observes about alterations in
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  // a container.
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  //
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  // The simple graphs can be refered as two containers: a node container
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  // and an edge container. But they do not store values directly, they
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  // are just key continars for more value containers, which are the
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  // node and edge maps.
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  //
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  // The node and edge sets of the graphs can be changed as we add or erase
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  // nodes and edges in the graph. LEMON would like to handle easily
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  // that the node and edge maps should contain values for all nodes or
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  // edges. If we want to check on every indicing if the map contains
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  // the current indicing key that cause a drawback in the performance
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  // in the library. We use another solution: we notify all maps about
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  // an alteration in the graph, which cause only drawback on the
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  // alteration of the graph.
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  //
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  // This class provides an interface to a node or edge container.
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  // The first() and next() member functions make possible
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  // to iterate on the keys of the container.
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  // The id() function returns an integer id for each key.
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  // The maxId() function gives back an upper bound of the ids.
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  //
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  // For the proper functonality of this class, we should notify it
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  // about each alteration in the container. The alterations have four type:
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  // add(), erase(), build() and clear(). The add() and
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  // erase() signal that only one or few items added or erased to or
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  // from the graph. If all items are erased from the graph or if a new graph
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  // is built from an empty graph, then it can be signaled with the
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  // clear() and build() members. Important rule that if we erase items
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  // from graphs we should first signal the alteration and after that erase
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  // them from the container, on the other way on item addition we should
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  // first extend the container and just after that signal the alteration.
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  //
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  // The alteration can be observed with a class inherited from the
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  // ObserverBase nested class. The signals can be handled with
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  // overriding the virtual functions defined in the base class.  The
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  // observer base can be attached to the notifier with the
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  // attach() member and can be detached with detach() function. The
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  // alteration handlers should not call any function which signals
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  // an other alteration in the same notifier and should not
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  // detach any observer from the notifier.
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  //
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  // Alteration observers try to be exception safe. If an add() or
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  // a clear() function throws an exception then the remaining
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  // observeres will not be notified and the fulfilled additions will
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  // be rolled back by calling the erase() or clear() functions.
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  // Hence erase() and clear() should not throw exception.
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  // Actullay, they can throw only \ref ImmediateDetach exception,
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  // which detach the observer from the notifier.
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  //
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  // There are some cases, when the alteration observing is not completly
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  // reliable. If we want to carry out the node degree in the graph
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  // as in the \ref InDegMap and we use the reverseArc(), then it cause
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  // unreliable functionality. Because the alteration observing signals
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  // only erasing and adding but not the reversing, it will stores bad
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  // degrees. Apart form that the subgraph adaptors cannot even signal
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  // the alterations because just a setting in the filter map can modify
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  // the graph and this cannot be watched in any way.
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  //
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  // \param _Container The container which is observed.
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  // \param _Item The item type which is obserbved.
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  template <typename _Container, typename _Item>
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  class AlterationNotifier {
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  public:
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    typedef True Notifier;
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    typedef _Container Container;
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    typedef _Item Item;
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    // \brief Exception which can be called from clear() and
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    // erase().
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    //
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    // From the clear() and erase() function only this
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    // exception is allowed to throw. The exception immediatly
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    // detaches the current observer from the notifier. Because the
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    // clear() and erase() should not throw other exceptions
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    // it can be used to invalidate the observer.
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    struct ImmediateDetach {};
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    // \brief ObserverBase is the base class for the observers.
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    //
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    // ObserverBase is the abstract base class for the observers.
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    // It will be notified about an item was inserted into or
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    // erased from the graph.
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    //
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    // The observer interface contains some pure virtual functions
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    // to override. The add() and erase() functions are
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    // to notify the oberver when one item is added or erased.
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    //
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    // The build() and clear() members are to notify the observer
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    // about the container is built from an empty container or
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    // is cleared to an empty container.
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    class ObserverBase {
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    protected:
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      typedef AlterationNotifier Notifier;
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      friend class AlterationNotifier;
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      // \brief Default constructor.
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      //
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      // Default constructor for ObserverBase.
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      ObserverBase() : _notifier(0) {}
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      // \brief Constructor which attach the observer into notifier.
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      //
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      // Constructor which attach the observer into notifier.
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      ObserverBase(AlterationNotifier& nf) {
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        attach(nf);
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      }
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      // \brief Constructor which attach the obserever to the same notifier.
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      //
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      // Constructor which attach the obserever to the same notifier as
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      // the other observer is attached to.
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      ObserverBase(const ObserverBase& copy) {
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        if (copy.attached()) {
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          attach(*copy.notifier());
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        }
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      }
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      // \brief Destructor
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      virtual ~ObserverBase() {
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        if (attached()) {
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          detach();
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        }
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      }
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      // \brief Attaches the observer into an AlterationNotifier.
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      //
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      // This member attaches the observer into an AlterationNotifier.
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      void attach(AlterationNotifier& nf) {
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        nf.attach(*this);
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      }
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      // \brief Detaches the observer into an AlterationNotifier.
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      //
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      // This member detaches the observer from an AlterationNotifier.
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      void detach() {
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        _notifier->detach(*this);
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      }
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      // \brief Gives back a pointer to the notifier which the map
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      // attached into.
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      //
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      // This function gives back a pointer to the notifier which the map
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      // attached into.
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      Notifier* notifier() const { return const_cast<Notifier*>(_notifier); }
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      // Gives back true when the observer is attached into a notifier.
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      bool attached() const { return _notifier != 0; }
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    private:
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      ObserverBase& operator=(const ObserverBase& copy);
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    protected:
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      Notifier* _notifier;
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      typename std::list<ObserverBase*>::iterator _index;
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      // \brief The member function to notificate the observer about an
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      // item is added to the container.
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      //
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      // The add() member function notificates the observer about an item
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      // is added to the container. It have to be overrided in the
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      // subclasses.
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      virtual void add(const Item&) = 0;
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      // \brief The member function to notificate the observer about
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      // more item is added to the container.
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      //
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      // The add() member function notificates the observer about more item
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      // is added to the container. It have to be overrided in the
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      // subclasses.
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      virtual void add(const std::vector<Item>& items) = 0;
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      // \brief The member function to notificate the observer about an
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      // item is erased from the container.
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      //
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      // The erase() member function notificates the observer about an
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      // item is erased from the container. It have to be overrided in
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      // the subclasses.
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      virtual void erase(const Item&) = 0;
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      // \brief The member function to notificate the observer about
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      // more item is erased from the container.
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      //
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      // The erase() member function notificates the observer about more item
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      // is erased from the container. It have to be overrided in the
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      // subclasses.
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      virtual void erase(const std::vector<Item>& items) = 0;
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      // \brief The member function to notificate the observer about the
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      // container is built.
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      //
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      // The build() member function notificates the observer about the
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      // container is built from an empty container. It have to be
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      // overrided in the subclasses.
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      virtual void build() = 0;
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      // \brief The member function to notificate the observer about all
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      // items are erased from the container.
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      //
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      // The clear() member function notificates the observer about all
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      // items are erased from the container. It have to be overrided in
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      // the subclasses.
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      virtual void clear() = 0;
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    };
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  protected:
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    const Container* container;
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    typedef std::list<ObserverBase*> Observers;
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    Observers _observers;
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  public:
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    // \brief Default constructor.
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    //
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    // The default constructor of the AlterationNotifier.
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    // It creates an empty notifier.
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    AlterationNotifier()
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      : container(0) {}
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    // \brief Constructor.
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    //
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    // Constructor with the observed container parameter.
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    AlterationNotifier(const Container& _container)
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      : container(&_container) {}
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    // \brief Copy Constructor of the AlterationNotifier.
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    //
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    // Copy constructor of the AlterationNotifier.
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    // It creates only an empty notifier because the copiable
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    // notifier's observers have to be registered still into that notifier.
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    AlterationNotifier(const AlterationNotifier& _notifier)
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      : container(_notifier.container) {}
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    // \brief Destructor.
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    //
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    // Destructor of the AlterationNotifier.
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    ~AlterationNotifier() {
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      typename Observers::iterator it;
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      for (it = _observers.begin(); it != _observers.end(); ++it) {
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        (*it)->_notifier = 0;
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      }
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    }
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    // \brief Sets the container.
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    //
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    // Sets the container.
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    void setContainer(const Container& _container) {
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      container = &_container;
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    }
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  protected:
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    AlterationNotifier& operator=(const AlterationNotifier&);
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  public:
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    // \brief First item in the container.
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    //
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    // Returns the first item in the container. It is
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    // for start the iteration on the container.
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    void first(Item& item) const {
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      container->first(item);
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    }
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    // \brief Next item in the container.
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    //
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    // Returns the next item in the container. It is
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    // for iterate on the container.
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    void next(Item& item) const {
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      container->next(item);
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    }
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    // \brief Returns the id of the item.
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    //
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    // Returns the id of the item provided by the container.
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    int id(const Item& item) const {
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      return container->id(item);
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    }
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    // \brief Returns the maximum id of the container.
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    //
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    // Returns the maximum id of the container.
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    int maxId() const {
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      return container->maxId(Item());
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    }
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  protected:
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    void attach(ObserverBase& observer) {
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      observer._index = _observers.insert(_observers.begin(), &observer);
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      observer._notifier = this;
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    }
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    void detach(ObserverBase& observer) {
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      _observers.erase(observer._index);
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      observer._index = _observers.end();
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      observer._notifier = 0;
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    }
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  public:
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    // \brief Notifies all the registed observers about an item added to
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    // the container.
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    //
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    // It notifies all the registed observers about an item added to
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    // the container.
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    void add(const Item& item) {
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      typename Observers::reverse_iterator it;
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      try {
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        for (it = _observers.rbegin(); it != _observers.rend(); ++it) {
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          (*it)->add(item);
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        }
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      } catch (...) {
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        typename Observers::iterator jt;
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        for (jt = it.base(); jt != _observers.end(); ++jt) {
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          (*jt)->erase(item);
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        }
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        throw;
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      }
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    }
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    // \brief Notifies all the registed observers about more item added to
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    // the container.
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    //
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    // It notifies all the registed observers about more item added to
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    // the container.
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    void add(const std::vector<Item>& items) {
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      typename Observers::reverse_iterator it;
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      try {
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        for (it = _observers.rbegin(); it != _observers.rend(); ++it) {
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          (*it)->add(items);
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        }
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      } catch (...) {
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        typename Observers::iterator jt;
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        for (jt = it.base(); jt != _observers.end(); ++jt) {
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          (*jt)->erase(items);
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        }
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        throw;
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      }
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    }
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    // \brief Notifies all the registed observers about an item erased from
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    // the container.
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    //
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    // It notifies all the registed observers about an item erased from
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    // the container.
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    void erase(const Item& item) throw() {
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      typename Observers::iterator it = _observers.begin();
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      while (it != _observers.end()) {
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        try {
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          (*it)->erase(item);
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          ++it;
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        } catch (const ImmediateDetach&) {
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          (*it)->_index = _observers.end();
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          (*it)->_notifier = 0;
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          it = _observers.erase(it);
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        }
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      }
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    }
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    // \brief Notifies all the registed observers about more item erased
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    // from the container.
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    //
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    // It notifies all the registed observers about more item erased from
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    // the container.
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    void erase(const std::vector<Item>& items) {
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      typename Observers::iterator it = _observers.begin();
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      while (it != _observers.end()) {
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        try {
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          (*it)->erase(items);
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          ++it;
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        } catch (const ImmediateDetach&) {
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          (*it)->_index = _observers.end();
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          (*it)->_notifier = 0;
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          it = _observers.erase(it);
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        }
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      }
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    }
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    // \brief Notifies all the registed observers about the container is
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    // built.
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    //
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    // Notifies all the registed observers about the container is built
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    // from an empty container.
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    void build() {
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      typename Observers::reverse_iterator it;
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      try {
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        for (it = _observers.rbegin(); it != _observers.rend(); ++it) {
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          (*it)->build();
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        }
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      } catch (...) {
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        typename Observers::iterator jt;
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        for (jt = it.base(); jt != _observers.end(); ++jt) {
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          (*jt)->clear();
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        }
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        throw;
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      }
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    }
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    // \brief Notifies all the registed observers about all items are
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    // erased.
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    //
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    // Notifies all the registed observers about all items are erased
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    // from the container.
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    void clear() {
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      typename Observers::iterator it = _observers.begin();
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      while (it != _observers.end()) {
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        try {
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   454
          (*it)->clear();
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          ++it;
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        } catch (const ImmediateDetach&) {
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          (*it)->_index = _observers.end();
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          (*it)->_notifier = 0;
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          it = _observers.erase(it);
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        }
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      }
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    }
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  };
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}
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#endif