_Self __tmp = *this;
    ++current;
    return __tmp;
  }

  _Self operator+(difference_type __n) const {
    return _Self(current - __n);
  }
  _Self& operator+=(difference_type __n) {
    current -= __n;
    return *this;
  }
  _Self operator-(difference_type __n) const {
    return _Self(current + __n);
  }
  _Self& operator-=(difference_type __n) {
    current += __n;
    return *this;
  }
  reference operator[](difference_type __n) const { return *(*this + __n); }  
}; 
 
template <class _Iterator>
inline bool operator==(const reverse_iterator<_Iterator>& __x, 
                       const reverse_iterator<_Iterator>& __y) {
  return __x.base() == __y.base();
}

template <class _Iterator>
inline bool operator<(const reverse_iterator<_Iterator>& __x, 
                      const reverse_iterator<_Iterator>& __y) {
  return __y.base() < __x.base();
}

#ifdef __STL_FUNCTION_TMPL_PARTIAL_ORDER

template <class _Iterator>
inline bool operator!=(const reverse_iterator<_Iterator>& __x, 
                       const reverse_iterator<_Iterator>& __y) {
  return !(__x == __y);
}

template <class _Iterator>
inline bool operator>(const reverse_iterator<_Iterator>& __x, 
                      const reverse_iterator<_Iterator>& __y) {
  return __y < __x;
}

template <class _Iterator>
inline bool operator<=(const reverse_iterator<_Iterator>& __x, 
                       const reverse_iterator<_Iterator>& __y) {
  return !(__y < __x);
}

template <class _Iterator>
inline bool operator>=(const reverse_iterator<_Iterator>& __x, 
                      const reverse_iterator<_Iterator>& __y) {
  return !(__x < __y);
}

#endif /* __STL_FUNCTION_TMPL_PARTIAL_ORDER */

template <class _Iterator>
inline typename reverse_iterator<_Iterator>::difference_type
operator-(const reverse_iterator<_Iterator>& __x, 
          const reverse_iterator<_Iterator>& __y) {
  return __y.base() - __x.base();
}

template <class _Iterator>
inline reverse_iterator<_Iterator> 
operator+(typename reverse_iterator<_Iterator>::difference_type __n,
          const reverse_iterator<_Iterator>& __x) {
  return reverse_iterator<_Iterator>(__x.base() - __n);
}

#else /* __STL_CLASS_PARTIAL_SPECIALIZATION */

// This is the old version of reverse_iterator, as found in the original
//  HP STL.  It does not use partial specialization.

#ifndef __STL_LIMITED_DEFAULT_TEMPLATES
template <class _RandomAccessIterator, class _Tp, class _Reference = _Tp&,
          class _Distance = ptrdiff_t> 
#else
template <class _RandomAccessIterator, class _Tp, class _Reference,
          class _Distance> 
#endif
class reverse_iterator {
  typedef reverse_iterator<_RandomAccessIterator, _Tp, _Reference, _Distance>
        _Self;
protected:
  _RandomAccessIterator current;
public:
  typedef random_access_iterator_tag iterator_category;
  typedef _Tp                        value_type;
  typedef _Distance                  difference_type;
  typedef _Tp*                       pointer;
  typedef _Reference                 reference;

  reverse_iterator() {}
  explicit reverse_iterator(_RandomAccessIterator __x) : current(__x) {}
  _RandomAccessIterator base() const { return current; }
  _Reference operator*() const { return *(current - 1); }
#ifndef __SGI_STL_NO_ARROW_OPERATOR
  pointer operator->() const { return &(operator*()); }
#endif /* __SGI_STL_NO_ARROW_OPERATOR */
  _Self& operator++() {
    --current;
    return *this;
  }
  _Self operator++(int) {
    _Self __tmp = *this;
    --current;
    return __tmp;
  }
  _Self& operator--() {
    ++current;
    return *this;
  }
  _Self operator--(int) {
    _Self __tmp = *this;
    ++current;
    return __tmp;
  }
  _Self operator+(_Distance __n) const {
    return _Self(current - __n);
  }
  _Self& operator+=(_Distance __n) {
    current -= __n;
    return *this;
  }
  _Self operator-(_Distance __n) const {
    return _Self(current + __n);
  }
  _Self& operator-=(_Distance __n) {
    current += __n;
    return *this;
  }
  _Reference operator[](_Distance __n) const { return *(*this + __n); }
};

template <class _RandomAccessIterator, class _Tp, 
          class _Reference, class _Distance>
inline random_access_iterator_tag
iterator_category(const reverse_iterator<_RandomAccessIterator, _Tp,
                                         _Reference, _Distance>&)
{
  return random_access_iterator_tag();
}

template <class _RandomAccessIterator, class _Tp,
          class _Reference, class _Distance>
inline _Tp* value_type(const reverse_iterator<_RandomAccessIterator, _Tp,
                                              _Reference, _Distance>&)
{
  return (_Tp*) 0;
}

template <class _RandomAccessIterator, class _Tp,
          class _Reference, class _Distance>
inline _Distance* 
distance_type(const reverse_iterator<_RandomAccessIterator, 
                                     _Tp, _Reference, _Distance>&)
{
  return (_Distance*) 0;
}


template <class _RandomAccessIterator, class _Tp,
          class _Reference, class _Distance>
inline bool 
operator==(const reverse_iterator<_RandomAccessIterator, _Tp,
                                  _Reference, _Distance>& __x, 
           const reverse_iterator<_RandomAccessIterator, _Tp,
                                  _Reference, _Distance>& __y)
{
  return __x.base() == __y.base();
}

template <class _RandomAccessIterator, class _Tp,
          class _Reference, class _Distance>
inline bool 
operator<(const reverse_iterator<_RandomAccessIterator, _Tp,
                                 _Reference, _Distance>& __x, 
          const reverse_iterator<_RandomAccessIterator, _Tp,
                                 _Reference, _Distance>& __y)
{
  return __y.base() < __x.base();
}

#ifdef __STL_FUNCTION_TMPL_PARTIAL_ORDER

template <class _RandomAccessIterator, class _Tp,
          class _Reference, class _Distance>
inline bool 
operator!=(const reverse_iterator<_RandomAccessIterator, _Tp,
                                  _Reference, _Distance>& __x, 
           const reverse_iterator<_RandomAccessIterator, _Tp,
                                  _Reference, _Distance>& __y) {
  return !(__x == __y); }
}

template <class _RandomAccessIterator, class _Tp,
          class _Reference, class _Distance>
inline bool 
operator>(const reverse_iterator<_RandomAccessIterator, _Tp,
                                 _Reference, _Distance>& __x, 
          const reverse_iterator<_RandomAccessIterator, _Tp,
                                 _Reference, _Distance>& __y) {
  return __y < __x;
}

template <class _RandomAccessIterator, class _Tp,
          class _Reference, class _Distance>
inline bool 
operator<=(const reverse_iterator<_RandomAccessIterator, _Tp,
                                  _Reference, _Distance>& __x, 
           const reverse_iterator<_RandomAccessIterator, _Tp,
                                  _Reference, _Distance>& __y) {
  return !(__y < __x);
}

template <class _RandomAccessIterator, class _Tp,
          class _Reference, class _Distance>
inline bool 
operator>=(const reverse_iterator<_RandomAccessIterator, _Tp,
                                  _Reference, _Distance>& __x, 
           const reverse_iterator<_RandomAccessIterator, _Tp,
                                  _Reference, _Distance>& __y) {
  return !(__x < __y);
}

#endif /* __STL_FUNCTION_TMPL_PARTIAL_ORDER */

template <class _RandomAccessIterator, class _Tp,
          class _Reference, class _Distance>
inline _Distance 
operator-(const reverse_iterator<_RandomAccessIterator, _Tp,
                                 _Reference, _Distance>& __x, 
          const reverse_iterator<_RandomAccessIterator, _Tp,
                                 _Reference, _Distance>& __y)
{
  return __y.base() - __x.base();
}

template <class _RandAccIter, class _Tp, class _Ref, class _Dist>
inline reverse_iterator<_RandAccIter, _Tp, _Ref, _Dist> 
operator+(_Dist __n,
          const reverse_iterator<_RandAccIter, _Tp, _Ref, _Dist>& __x)
{
  return reverse_iterator<_RandAccIter, _Tp, _Ref, _Dist>(__x.base() - __n);
}

#endif /* __STL_CLASS_PARTIAL_SPECIALIZATION */

// istream_iterator and ostream_iterator look very different if we're
// using new, templatized iostreams than if we're using the old cfront
// version.

#ifdef __STL_USE_NEW_IOSTREAMS

template <class _Tp, 
          class _CharT = char, class _Traits = char_traits<_CharT>,
          class _Dist = ptrdiff_t> 
class istream_iterator {
public:
  typedef _CharT                         char_type;
  typedef _Traits                        traits_type;
  typedef basic_istream<_CharT, _Traits> istream_type;

  typedef input_iterator_tag             iterator_category;
  typedef _Tp                            value_type;
  typedef _Dist                          difference_type;
  typedef const _Tp*                     pointer;
  typedef const _Tp&                     reference;

  istream_iterator() : _M_stream(0), _M_ok(false) {}
  istream_iterator(istream_type& __s) : _M_stream(&__s) { _M_read(); }

  reference operator*() const { return _M_value; }
  pointer operator->() const { return &(operator*()); }

  istream_iterator& operator++() { 
    _M_read(); 
    return *this;
  }
  istream_iterator operator++(int)  {
    istream_iterator __tmp = *this;
    _M_read();
    return __tmp;
  }

  bool _M_equal(const istream_iterator& __x) const
    { return (_M_ok == __x._M_ok) && (!_M_ok || _M_stream == __x._M_stream); }

private:
  istream_type* _M_stream;
  _Tp _M_value;
  bool _M_ok;

  void _M_read() {
    _M_ok = (_M_stream && *_M_stream) ? true : false;
    if (_M_ok) {
      *_M_stream >> _M_value;
      _M_ok = *_M_stream ? true : false;
    }
  }
};

template <class _Tp, class _CharT, class _Traits, class _Dist>
inline bool 
operator==(const istream_iterator<_Tp, _CharT, _Traits, _Dist>& __x,
           const istream_iterator<_Tp, _CharT, _Traits, _Dist>& __y) {
  return __x._M_equal(__y);
}

#ifdef __STL_FUNCTION_TMPL_PARTIAL_ORDER

template <class _Tp, class _CharT, class _Traits, class _Dist>
inline bool 
operator!=(const istream_iterator<_Tp, _CharT, _Traits, _Dist>& __x,
           const istream_iterator<_Tp, _CharT, _Traits, _Dist>& __y) {
  return !__x._M_equal(__y);
}