support.hh

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// support.hh: this file is part of the Vaucanson project.
//
// Vaucanson, a generic library for finite state machines.
//
// Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007 The Vaucanson Group.
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// The complete GNU General Public Licence Notice can be found as the
// `COPYING' file in the root directory.
//
// The Vaucanson Group consists of people listed in the `AUTHORS' file.
//
#ifndef VCSN_MISC_SUPPORT_HH
# define VCSN_MISC_SUPPORT_HH

# include <iterator>
# include <map>
# include <string>

namespace vcsn
{
  namespace misc
  {

    template <class T>
    class Support;

    template <class C>
    class SupportIterator
    {
      public:
        typedef typename C::key_type            key_type;
        typedef typename C::const_iterator      map_iterator;
        typedef SupportIterator<C>              self_t;

        typedef typename map_iterator::iterator_category iterator_category;
        typedef typename map_iterator::difference_type   difference_type;
        typedef key_type                                 value_type;
        typedef key_type*                                pointer;
        typedef key_type&                                reference;

        /*
         * This is a default constructor. 
         * WARNING: this constructor instantiates an invalid iterator.
         *          To use an iterator instantiated by this constructor,
         *          you need to initialize it thanks to the '=' operator.
         *
         * This constructor is useful whenever you want to use an iterator as
         * a temporary variable in a loop. For instance:
         *
         * for (SupportIterator tmp, it = aut.final().begin(); 
         *      it != aut.final().end();)
         * {
         *      tmp = it++;
         *      if (something)
         *              del_state(*tmp);
         * }
         *
         * In this example, we delete an object in a set we are already iterating on.
         * So we need to save a copy of the next element before deleting the current one.
         * Since declaring a temporary variable inside a loop can slow down performances,
         * it is declared inside the 'for loop' declaration and, in that case, we are really
         * interested in such a constructor.
         *
         */
        SupportIterator () {}
        SupportIterator (map_iterator);

        key_type operator* () const;
        self_t&  operator++ ();
        self_t   operator++ (int);
        bool     operator!= (const SupportIterator&) const;
        bool     operator== (const SupportIterator&) const;

      private:
        map_iterator    i;
    };

    template <class U, class T>
    class Support<std::map<U, T> >
    {
      public:
        typedef SupportIterator<std::map<U, T> > iterator;
        typedef SupportIterator<std::map<U, T> > const_iterator;
        typedef typename std::map<U, T>::value_type value_type;

        Support (const std::map<U, T>&);
        Support (const Support&);

        value_type operator* () const;

        iterator begin () const;
        iterator end () const;
        unsigned size () const;

        // Find the element associated to \a k.
        iterator find (const U& k) const;

        bool empty () const;

        U max () const;
      private:
        const std::map<U, T>&   m_;
    };

  } // misc
} // vcsn

# if !defined VCSN_USE_INTERFACE_ONLY || defined VCSN_USE_LIB
#  include <vaucanson/misc/support.hxx>
# endif // VCSN_USE_INTERFACE_ONLY


#endif // ! VCSN_MISC_SUPPORT_HH

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