stl_iterator.h

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    };

  /**
   *  @param  x  A container of arbitrary type.
   *  @return  An instance of back_insert_iterator working on @p x.
   *
   *  This wrapper function helps in creating back_insert_iterator instances.
   *  Typing the name of the %iterator requires knowing the precise full
   *  type of the container, which can be tedious and impedes generic
   *  programming.  Using this function lets you take advantage of automatic
   *  template parameter deduction, making the compiler match the correct
   *  types for you.
  */
  template<typename _Container>
    inline back_insert_iterator<_Container> 
    back_inserter(_Container& __x) 
    { return back_insert_iterator<_Container>(__x); }

  /**
   *  @brief  Turns assignment into insertion.
   *
   *  These are output iterators, constructed from a container-of-T.
   *  Assigning a T to the iterator prepends it to the container using
   *  push_front.
   *
   *  Tip:  Using the front_inserter function to create these iterators can
   *  save typing.
  */
  template<typename _Container>
    class front_insert_iterator 
    : public iterator<output_iterator_tag, void, void, void, void>
    {
    protected:
      _Container* container;

    public:
      /// A nested typedef for the type of whatever container you used.
      typedef _Container          container_type;

      /// The only way to create this %iterator is with a container.
      explicit front_insert_iterator(_Container& __x) : container(&__x) { }

      /**
       *  @param  value  An instance of whatever type
       *                 container_type::const_reference is; presumably a
       *                 reference-to-const T for container<T>.
       *  @return  This %iterator, for chained operations.
       *
       *  This kind of %iterator doesn't really have a "position" in the
       *  container (you can think of the position as being permanently at
       *  the front, if you like).  Assigning a value to the %iterator will
       *  always prepend the value to the front of the container.
      */
      front_insert_iterator&
      operator=(typename _Container::const_reference __value) 
      { 
	container->push_front(__value);
	return *this;
      }

      /// Simply returns *this.
      front_insert_iterator& 
      operator*() { return *this; }

      /// Simply returns *this.  (This %iterator does not "move".)
      front_insert_iterator& 
      operator++() { return *this; }

      /// Simply returns *this.  (This %iterator does not "move".)
      front_insert_iterator 
      operator++(int) { return *this; }
    };

  /**
   *  @param  x  A container of arbitrary type.
   *  @return  An instance of front_insert_iterator working on @p x.
   *
   *  This wrapper function helps in creating front_insert_iterator instances.
   *  Typing the name of the %iterator requires knowing the precise full
   *  type of the container, which can be tedious and impedes generic
   *  programming.  Using this function lets you take advantage of automatic
   *  template parameter deduction, making the compiler match the correct
   *  types for you.
  */
  template<typename _Container>
    inline front_insert_iterator<_Container> 
    front_inserter(_Container& __x) 
    { return front_insert_iterator<_Container>(__x); }

  /**
   *  @brief  Turns assignment into insertion.
   *
   *  These are output iterators, constructed from a container-of-T.
   *  Assigning a T to the iterator inserts it in the container at the
   *  %iterator's position, rather than overwriting the value at that
   *  position.
   *
   *  (Sequences will actually insert a @e copy of the value before the
   *  %iterator's position.)
   *
   *  Tip:  Using the inserter function to create these iterators can
   *  save typing.
  */
  template<typename _Container>
    class insert_iterator 
    : public iterator<output_iterator_tag, void, void, void, void>
    {
    protected:
      _Container* container;
      typename _Container::iterator iter;

    public:
      /// A nested typedef for the type of whatever container you used.
      typedef _Container          container_type;
      
      /**
       *  The only way to create this %iterator is with a container and an
       *  initial position (a normal %iterator into the container).
      */
      insert_iterator(_Container& __x, typename _Container::iterator __i) 
      : container(&__x), iter(__i) {}
   
      /**
       *  @param  value  An instance of whatever type
       *                 container_type::const_reference is; presumably a
       *                 reference-to-const T for container<T>.
       *  @return  This %iterator, for chained operations.
       *
       *  This kind of %iterator maintains its own position in the
       *  container.  Assigning a value to the %iterator will insert the
       *  value into the container at the place before the %iterator.
       *
       *  The position is maintained such that subsequent assignments will
       *  insert values immediately after one another.  For example,
       *  @code
       *     // vector v contains A and Z
       *
       *     insert_iterator i (v, ++v.begin());
       *     i = 1;
       *     i = 2;
       *     i = 3;
       *
       *     // vector v contains A, 1, 2, 3, and Z
       *  @endcode
      */
      insert_iterator&
      operator=(const typename _Container::const_reference __value) 
      { 
	iter = container->insert(iter, __value);
	++iter;
	return *this;
      }

      /// Simply returns *this.
      insert_iterator& 
      operator*() { return *this; }

      /// Simply returns *this.  (This %iterator does not "move".)
      insert_iterator& 
      operator++() { return *this; }

      /// Simply returns *this.  (This %iterator does not "move".)
      insert_iterator& 
      operator++(int) { return *this; }
    };
  
  /**
   *  @param  x  A container of arbitrary type.
   *  @return  An instance of insert_iterator working on @p x.
   *
   *  This wrapper function helps in creating insert_iterator instances.
   *  Typing the name of the %iterator requires knowing the precise full
   *  type of the container, which can be tedious and impedes generic
   *  programming.  Using this function lets you take advantage of automatic
   *  template parameter deduction, making the compiler match the correct
   *  types for you.
  */
  template<typename _Container, typename _Iterator>
    inline insert_iterator<_Container> 
    inserter(_Container& __x, _Iterator __i)
    {
      return insert_iterator<_Container>(__x, 
					 typename _Container::iterator(__i));
    }
} // namespace std

namespace __gnu_cxx
{  
  // This iterator adapter is 'normal' in the sense that it does not
  // change the semantics of any of the operators of its iterator
  // parameter.  Its primary purpose is to convert an iterator that is
  // not a class, e.g. a pointer, into an iterator that is a class.
  // The _Container parameter exists solely so that different containers
  // using this template can instantiate different types, even if the
  // _Iterator parameter is the same.
  using std::iterator_traits;
  using std::iterator;
  template<typename _Iterator, typename _Container>
    class __normal_iterator
      : public iterator<typename iterator_traits<_Iterator>::iterator_category,
                        typename iterator_traits<_Iterator>::value_type,
                        typename iterator_traits<_Iterator>::difference_type,
                        typename iterator_traits<_Iterator>::pointer,
                        typename iterator_traits<_Iterator>::reference>
    {
    protected:
      _Iterator _M_current;
      
    public:
      typedef typename iterator_traits<_Iterator>::difference_type 	
      							       difference_type;
      typedef typename iterator_traits<_Iterator>::reference   reference;
      typedef typename iterator_traits<_Iterator>::pointer     pointer;

      __normal_iterator() : _M_current(_Iterator()) { }

      explicit 
      __normal_iterator(const _Iterator& __i) : _M_current(__i) { }

      // Allow iterator to const_iterator conversion
      template<typename _Iter>
      inline __normal_iterator(const __normal_iterator<_Iter, _Container>& __i)
	: _M_current(__i.base()) { }

      // Forward iterator requirements
      reference
      operator*() const { return *_M_current; }
      
      pointer
      operator->() const { return _M_current; }
      
      __normal_iterator&
      operator++() { ++_M_current; return *this; }
      
      __normal_iterator
      operator++(int) { return __normal_iterator(_M_current++); }
      
      // Bidirectional iterator requirements
      __normal_iterator&
      operator--() { --_M_current; return *this; }
      
      __normal_iterator
      operator--(int) { return __normal_iterator(_M_current--); }
      
      // Random access iterator requirements
      reference
      operator[](const difference_type& __n) const
      { return _M_current[__n]; }
      
      __normal_iterator&
      operator+=(const difference_type& __n)
      { _M_current += __n; return *this; }

      __normal_iterator
      operator+(const difference_type& __n) const
      { return __normal_iterator(_M_current + __n); }
      
      __normal_iterator&
      operator-=(const difference_type& __n)
      { _M_current -= __n; return *this; }
      
      __normal_iterator
      operator-(const difference_type& __n) const
      { return __normal_iterator(_M_current - __n); }
      
      const _Iterator& 
      base() const { return _M_current; }
    };

  // Note: In what follows, the left- and right-hand-side iterators are
  // allowed to vary in types (conceptually in cv-qualification) so that
  // comparaison between cv-qualified and non-cv-qualified iterators be
  // valid.  However, the greedy and unfriendly operators in std::rel_ops
  // will make overload resolution ambiguous (when in scope) if we don't
  // provide overloads whose operands are of the same type.  Can someone
  // remind me what generic programming is about? -- Gaby
  
  // Forward iterator requirements
  template<typename _IteratorL, typename _IteratorR, typename _Container>
  inline bool
  operator==(const __normal_iterator<_IteratorL, _Container>& __lhs,
	     const __normal_iterator<_IteratorR, _Container>& __rhs)
  { return __lhs.base() == __rhs.base(); }

  template<typename _Iterator, typename _Container>
  inline bool
  operator==(const __normal_iterator<_Iterator, _Container>& __lhs,
             const __normal_iterator<_Iterator, _Container>& __rhs)
  { return __lhs.base() == __rhs.base(); }

  template<typename _IteratorL, typename _IteratorR, typename _Container>
  inline bool
  operator!=(const __normal_iterator<_IteratorL, _Container>& __lhs,
	     const __normal_iterator<_IteratorR, _Container>& __rhs)
  { return __lhs.base() != __rhs.base(); }

  template<typename _Iterator, typename _Container>
  inline bool
  operator!=(const __normal_iterator<_Iterator, _Container>& __lhs,
             const __normal_iterator<_Iterator, _Container>& __rhs)
  { return __lhs.base() != __rhs.base(); }

  // Random access iterator requirements
  template<typename _IteratorL, typename _IteratorR, typename _Container>
  inline bool 
  operator<(const __normal_iterator<_IteratorL, _Container>& __lhs,
	    const __normal_iterator<_IteratorR, _Container>& __rhs)
  { return __lhs.base() < __rhs.base(); }

  template<typename _Iterator, typename _Container>
  inline bool
  operator<(const __normal_iterator<_Iterator, _Container>& __lhs,
             const __normal_iterator<_Iterator, _Container>& __rhs)
  { return __lhs.base() < __rhs.base(); }

  template<typename _IteratorL, typename _IteratorR, typename _Container>
  inline bool
  operator>(const __normal_iterator<_IteratorL, _Container>& __lhs,
	    const __normal_iterator<_IteratorR, _Container>& __rhs)
  { return __lhs.base() > __rhs.base(); }

  template<typename _Iterator, typename _Container>
  inline bool
  operator>(const __normal_iterator<_Iterator, _Container>& __lhs,
	    const __normal_iterator<_Iterator, _Container>& __rhs)
  { return __lhs.base() > __rhs.base(); }

  template<typename _IteratorL, typename _IteratorR, typename _Container>
  inline bool
  operator<=(const __normal_iterator<_IteratorL, _Container>& __lhs,
	     const __normal_iterator<_IteratorR, _Container>& __rhs)
  { return __lhs.base() <= __rhs.base(); }

  template<typename _Iterator, typename _Container>
  inline bool
  operator<=(const __normal_iterator<_Iterator, _Container>& __lhs,
	     const __normal_iterator<_Iterator, _Container>& __rhs)
  { return __lhs.base() <= __rhs.base(); }

  template<typename _IteratorL, typename _IteratorR, typename _Container>
  inline bool
  operator>=(const __normal_iterator<_IteratorL, _Container>& __lhs,
	     const __normal_iterator<_IteratorR, _Container>& __rhs)
  { return __lhs.base() >= __rhs.base(); }

  template<typename _Iterator, typename _Container>
  inline bool
  operator>=(const __normal_iterator<_Iterator, _Container>& __lhs,
	     const __normal_iterator<_Iterator, _Container>& __rhs)
  { return __lhs.base() >= __rhs.base(); }

  // _GLIBCPP_RESOLVE_LIB_DEFECTS
  // According to the resolution of DR179 not only the various comparison
  // operators but also operator- must accept mixed iterator/const_iterator
  // parameters.
  template<typename _IteratorL, typename _IteratorR, typename _Container>
  inline typename __normal_iterator<_IteratorL, _Container>::difference_type
  operator-(const __normal_iterator<_IteratorL, _Container>& __lhs,
	     const __normal_iterator<_IteratorR, _Container>& __rhs)
  { return __lhs.base() - __rhs.base(); }

  template<typename _Iterator, typename _Container>
  inline __normal_iterator<_Iterator, _Container>
  operator+(typename __normal_iterator<_Iterator, _Container>::difference_type __n,
	    const __normal_iterator<_Iterator, _Container>& __i)
  { return __normal_iterator<_Iterator, _Container>(__i.base() + __n); }
} // namespace __gnu_cxx

#endif 

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