// Algorithm extensions -*- C++ -*-

// Copyright (C) 2001, 2002 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library 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, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

/*
 *
 * Copyright (c) 1994
 * Hewlett-Packard Company
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Hewlett-Packard Company makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 *
 * Copyright (c) 1996
 * Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Silicon Graphics makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 */

/** @file ext/algorithm
 *  This file is a GNU extension to the Standard C++ Library (possibly
 *  containing extensions from the HP/SGI STL subset).  You should only
 *  include this header if you are using GCC 3 or later.
 */

#ifndef _EXT_ALGORITHM
#define _EXT_ALGORITHM

#pragma GCC system_header
#include <algorithm>

namespace __gnu_cxx
{
  using std::ptrdiff_t;
  using std::min;
  using std::pair;
  using std::input_iterator_tag;
  using std::random_access_iterator_tag;
  using std::iterator_traits;

  //--------------------------------------------------
  // copy_n (not part of the C++ standard)

  template<typename _InputIter, typename _Size, typename _OutputIter>
    pair<_InputIter, _OutputIter>
    __copy_n(_InputIter __first, _Size __count,
	     _OutputIter __result,
	     input_iterator_tag)
    {
      for ( ; __count > 0; --__count) {
	*__result = *__first;
	++__first;
	++__result;
      }
      return pair<_InputIter, _OutputIter>(__first, __result);
    }

  template<typename _RAIter, typename _Size, typename _OutputIter>
    inline pair<_RAIter, _OutputIter>
    __copy_n(_RAIter __first, _Size __count,
	     _OutputIter __result,
	     random_access_iterator_tag)
    {
      _RAIter __last = __first + __count;
      return pair<_RAIter, _OutputIter>(__last,
					std::copy(__first, __last, __result));
    }

  /**
   *  @brief Copies the range [first,first+count) into [result,result+count).
   *  @param  first  An input iterator.
   *  @param  count  The number of elements to copy.
   *  @param  result An output iterator.
   *  @return   A std::pair composed of first+count and result+count.
   *
   *  This is an SGI extension.
   *  This inline function will boil down to a call to @c memmove whenever
   *  possible.  Failing that, if random access iterators are passed, then the
   *  loop count will be known (and therefore a candidate for compiler
   *  optimizations such as unrolling).
   *  @ingroup SGIextensions
  */
  template<typename _InputIter, typename _Size, typename _OutputIter>
    inline pair<_InputIter, _OutputIter>
    copy_n(_InputIter __first, _Size __count, _OutputIter __result)
    {
      // concept requirements
      __glibcpp_function_requires(_InputIteratorConcept<_InputIter>)
      __glibcpp_function_requires(_OutputIteratorConcept<_OutputIter,
	    typename iterator_traits<_InputIter>::value_type>)

      return __copy_n(__first, __count, __result,
		      std::__iterator_category(__first));
    }

  template<typename _InputIter1, typename _InputIter2>
    int
    __lexicographical_compare_3way(_InputIter1 __first1, _InputIter1 __last1,
				   _InputIter2 __first2, _InputIter2 __last2)
    {
      while (__first1 != __last1 && __first2 != __last2) {
	if (*__first1 < *__first2)
	  return -1;
	if (*__first2 < *__first1)
	  return 1;
	++__first1;
	++__first2;
      }
      if (__first2 == __last2) {
	return !(__first1 == __last1);
      }
      else {
	return -1;
      }
    }

  inline int
  __lexicographical_compare_3way(const unsigned char* __first1,
				 const unsigned char* __last1,
				 const unsigned char* __first2,
				 const unsigned char* __last2)
  {
    const ptrdiff_t __len1 = __last1 - __first1;
    const ptrdiff_t __len2 = __last2 - __first2;
    const int __result = std::memcmp(__first1, __first2, min(__len1, __len2));
    return __result != 0 ? __result 
			 : (__len1 == __len2 ? 0 : (__len1 < __len2 ? -1 : 1));
  }

  inline int 
  __lexicographical_compare_3way(const char* __first1, const char* __last1,
				 const char* __first2, const char* __last2)
  {
#if CHAR_MAX == SCHAR_MAX
    return __lexicographical_compare_3way(
				  (const signed char*) __first1,
				  (const signed char*) __last1,
				  (const signed char*) __first2,
				  (const signed char*) __last2);
#else
    return __lexicographical_compare_3way((const unsigned char*) __first1,
					  (const unsigned char*) __last1,
					  (const unsigned char*) __first2,
					  (const unsigned char*) __last2);
#endif
  }

  /**
   *  @brief @c memcmp on steroids.
   *  @param  first1  An input iterator.
   *  @param  last1   An input iterator.
   *  @param  first2  An input iterator.
   *  @param  last2   An input iterator.
   *  @return   An int, as with @c memcmp.
   *
   *  The return value will be less than zero if the first range is
   *  "lexigraphically less than" the second, greater than zero if the second
   *  range is "lexigraphically less than" the first, and zero otherwise.
   *  This is an SGI extension.
   *  @ingroup SGIextensions
  */
  template<typename _InputIter1, typename _InputIter2>
    int
    lexicographical_compare_3way(_InputIter1 __first1, _InputIter1 __last1,
				 _InputIter2 __first2, _InputIter2 __last2)
    {
      // concept requirements
      __glibcpp_function_requires(_InputIteratorConcept<_InputIter1>)
      __glibcpp_function_requires(_InputIteratorConcept<_InputIter2>)
      __glibcpp_function_requires(_LessThanComparableConcept<
	    typename iterator_traits<_InputIter1>::value_type>)
      __glibcpp_function_requires(_LessThanComparableConcept<
	    typename iterator_traits<_InputIter2>::value_type>)

      return __lexicographical_compare_3way(__first1, __last1, __first2, __last2);
    }

  // count and count_if: this version, whose return type is void, was present
  // in the HP STL, and is retained as an extension for backward compatibility.

  template<typename _InputIter, typename _Tp, typename _Size>
    void
    count(_InputIter __first, _InputIter __last,
	  const _Tp& __value,
	  _Size& __n)
    {
      // concept requirements
      __glibcpp_function_requires(_InputIteratorConcept<_InputIter>)
      __glibcpp_function_requires(_EqualityComparableConcept<
	    typename iterator_traits<_InputIter>::value_type >)
      __glibcpp_function_requires(_EqualityComparableConcept<_Tp>)
      for ( ; __first != __last; ++__first)
	if (*__first == __value)
	  ++__n;
    }

  template<typename _InputIter, typename _Predicate, typename _Size>
    void
    count_if(_InputIter __first, _InputIter __last,
	     _Predicate __pred,
	     _Size& __n)
    {
      // concept requirements
      __glibcpp_function_requires(_InputIteratorConcept<_InputIter>)
      __glibcpp_function_requires(_UnaryPredicateConcept<_Predicate,
	    typename iterator_traits<_InputIter>::value_type>)
      for ( ; __first != __last; ++__first)
	if (__pred(*__first))
	  ++__n;
    }

  // random_sample and random_sample_n (extensions, not part of the standard).

  template<typename _ForwardIter, typename _OutputIter, typename _Distance>
    _OutputIter
    random_sample_n(_ForwardIter __first, _ForwardIter __last,
                    _OutputIter __out, const _Distance __n)
    {
      // concept requirements
      __glibcpp_function_requires(_ForwardIteratorConcept<_ForwardIter>)
      __glibcpp_function_requires(_OutputIteratorConcept<_OutputIter,
		typename iterator_traits<_ForwardIter>::value_type>)

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

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

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

  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;
    }

  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);
    }

  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;
    }

  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);
    }

  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.

  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;
    }

  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 */
