algorithm

俄罗斯高人Mamaich的Pocket gcc编译器（运行在PocketPC上）的全部源代码。

	      *__out = *__first;
	      ++__out;
	      --__m;
	}

	--__remaining;
	++__first;
      }
      return __out;
    }

  /**
   *  This is an SGI extension.
   *  @ingroup SGIextensions
   *  @doctodo
  */
  template<typename _ForwardIter, typename _OutputIter, typename _Distance,
	   typename _RandomNumberGenerator>
    _OutputIter
    random_sample_n(_ForwardIter __first, _ForwardIter __last,
                   _OutputIter __out, const _Distance __n, 
		   _RandomNumberGenerator& __rand)
    {
      // concept requirements
      __glibcpp_function_requires(_ForwardIteratorConcept<_ForwardIter>)
      __glibcpp_function_requires(_OutputIteratorConcept<_OutputIter,
		typename iterator_traits<_ForwardIter>::value_type>)
      __glibcpp_function_requires(_UnaryFunctionConcept<
		_RandomNumberGenerator, _Distance, _Distance>)

      _Distance __remaining = std::distance(__first, __last);
      _Distance __m = min(__n, __remaining);

      while (__m > 0) {
	if (__rand(__remaining) < __m) {
	      *__out = *__first;
	      ++__out;
	      --__m;
	}

	--__remaining;
	++__first;
      }
      return __out;
    }

  template<typename _InputIter, typename _RandomAccessIter, typename _Distance>
    _RandomAccessIter
    __random_sample(_InputIter __first, _InputIter __last,
		    _RandomAccessIter __out,
		    const _Distance __n)
    {
      _Distance __m = 0;
      _Distance __t = __n;
      for ( ; __first != __last && __m < __n; ++__m, ++__first) 
	__out[__m] = *__first;

      while (__first != __last) {
	++__t;
	_Distance __M = std::__random_number(__t);
	if (__M < __n)
	  __out[__M] = *__first;
	++__first;
      }

      return __out + __m;
    }

  template<typename _InputIter, typename _RandomAccessIter,
	   typename _RandomNumberGenerator, typename _Distance>
    _RandomAccessIter
    __random_sample(_InputIter __first, _InputIter __last,
		    _RandomAccessIter __out,
		    _RandomNumberGenerator& __rand,
		    const _Distance __n)
    {
      // concept requirements
      __glibcpp_function_requires(_UnaryFunctionConcept<
	    _RandomNumberGenerator, _Distance, _Distance>)

      _Distance __m = 0;
      _Distance __t = __n;
      for ( ; __first != __last && __m < __n; ++__m, ++__first)
	__out[__m] = *__first;

      while (__first != __last) {
	++__t;
	_Distance __M = __rand(__t);
	if (__M < __n)
	  __out[__M] = *__first;
	++__first;
      }

      return __out + __m;
    }

  /**
   *  This is an SGI extension.
   *  @ingroup SGIextensions
   *  @doctodo
  */
  template<typename _InputIter, typename _RandomAccessIter>
    inline _RandomAccessIter
    random_sample(_InputIter __first, _InputIter __last,
		  _RandomAccessIter __out_first, _RandomAccessIter __out_last) 
    {
      // concept requirements
      __glibcpp_function_requires(_InputIteratorConcept<_InputIter>)
      __glibcpp_function_requires(_Mutable_RandomAccessIteratorConcept<
	    _RandomAccessIter>)

      return __random_sample(__first, __last,
			     __out_first, __out_last - __out_first);
    }

  /**
   *  This is an SGI extension.
   *  @ingroup SGIextensions
   *  @doctodo
  */
  template<typename _InputIter, typename _RandomAccessIter, 
	   typename _RandomNumberGenerator>
    inline _RandomAccessIter
    random_sample(_InputIter __first, _InputIter __last,
		  _RandomAccessIter __out_first, _RandomAccessIter __out_last,
		  _RandomNumberGenerator& __rand) 
    {
      // concept requirements
      __glibcpp_function_requires(_InputIteratorConcept<_InputIter>)
      __glibcpp_function_requires(_Mutable_RandomAccessIteratorConcept<
	    _RandomAccessIter>)

      return __random_sample(__first, __last,
			     __out_first, __rand,
			     __out_last - __out_first);
    }
  
  // is_heap, a predicate testing whether or not a range is
  // a heap.  This function is an extension, not part of the C++
  // standard.

  template<typename _RandomAccessIter, typename _Distance>
    bool
    __is_heap(_RandomAccessIter __first, _Distance __n)
    {
      _Distance __parent = 0;
      for (_Distance __child = 1; __child < __n; ++__child) {
	if (__first[__parent] < __first[__child]) 
	  return false;
	if ((__child & 1) == 0)
	  ++__parent;
      }
      return true;
    }

  template<typename _RandomAccessIter, typename _Distance,
           typename _StrictWeakOrdering>
    bool
    __is_heap(_RandomAccessIter __first, _StrictWeakOrdering __comp,
	      _Distance __n)
    {
      _Distance __parent = 0;
      for (_Distance __child = 1; __child < __n; ++__child) {
	if (__comp(__first[__parent], __first[__child]))
	  return false;
	if ((__child & 1) == 0)
	  ++__parent;
      }
      return true;
    }

  /**
   *  This is an SGI extension.
   *  @ingroup SGIextensions
   *  @doctodo
  */
  template<typename _RandomAccessIter>
    inline bool
    is_heap(_RandomAccessIter __first, _RandomAccessIter __last)
    {
      // concept requirements
      __glibcpp_function_requires(_RandomAccessIteratorConcept<_RandomAccessIter>)
      __glibcpp_function_requires(_LessThanComparableConcept<
	    typename iterator_traits<_RandomAccessIter>::value_type>)

      return __is_heap(__first, __last - __first);
    }

  /**
   *  This is an SGI extension.
   *  @ingroup SGIextensions
   *  @doctodo
  */
  template<typename _RandomAccessIter, typename _StrictWeakOrdering>
    inline bool
    is_heap(_RandomAccessIter __first, _RandomAccessIter __last,
	    _StrictWeakOrdering __comp)
    {
      // concept requirements
      __glibcpp_function_requires(_RandomAccessIteratorConcept<_RandomAccessIter>)
      __glibcpp_function_requires(_BinaryPredicateConcept<_StrictWeakOrdering,
	    typename iterator_traits<_RandomAccessIter>::value_type, 
	    typename iterator_traits<_RandomAccessIter>::value_type>)

      return __is_heap(__first, __comp, __last - __first);
    }

  // is_sorted, a predicated testing whether a range is sorted in
  // nondescending order.  This is an extension, not part of the C++
  // standard.

  /**
   *  This is an SGI extension.
   *  @ingroup SGIextensions
   *  @doctodo
  */
  template<typename _ForwardIter>
    bool
    is_sorted(_ForwardIter __first, _ForwardIter __last)
    {
      // concept requirements
      __glibcpp_function_requires(_ForwardIteratorConcept<_ForwardIter>)
      __glibcpp_function_requires(_LessThanComparableConcept<
	    typename iterator_traits<_ForwardIter>::value_type>)

      if (__first == __last)
	return true;

      _ForwardIter __next = __first;
      for (++__next; __next != __last; __first = __next, ++__next) {
	if (*__next < *__first)
	  return false;
      }

      return true;
    }

  /**
   *  This is an SGI extension.
   *  @ingroup SGIextensions
   *  @doctodo
  */
  template<typename _ForwardIter, typename _StrictWeakOrdering>
    bool
    is_sorted(_ForwardIter __first, _ForwardIter __last, _StrictWeakOrdering __comp)
    {
      // concept requirements
      __glibcpp_function_requires(_ForwardIteratorConcept<_ForwardIter>)
      __glibcpp_function_requires(_BinaryPredicateConcept<_StrictWeakOrdering,
	    typename iterator_traits<_ForwardIter>::value_type, 
	    typename iterator_traits<_ForwardIter>::value_type>)

      if (__first == __last)
	return true;

      _ForwardIter __next = __first;
      for (++__next; __next != __last; __first = __next, ++__next) {
	if (__comp(*__next, *__first))
	  return false;
      }

      return true;
    }

} // namespace __gnu_cxx

#endif /* _EXT_ALGORITHM */