gcc/libstdc++-v3/include/bits/stl_algobase.h

/*
 *
 * 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) 1996-1998
 * 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.
 */

/* NOTE: This is an internal header file, included by other STL headers.
 *   You should not attempt to use it directly.
 */


#ifndef __SGI_STL_INTERNAL_ALGOBASE_H
#define __SGI_STL_INTERNAL_ALGOBASE_H

#include <bits/stl_config.h>
#include <bits/stl_relops.h>
#ifndef __SGI_STL_INTERNAL_PAIR_H
#include <bits/stl_pair.h>
#endif
#ifndef _CPP_BITS_TYPE_TRAITS_H
#include <bits/type_traits.h>
#endif
#include <bits/std_cstring.h>
#include <bits/std_climits.h>
#include <bits/std_cstdlib.h>
#include <bits/std_cstddef.h>
#include <new>

#ifdef __STL_USE_NEW_IOSTREAMS 
#include <iosfwd>
#else /* __STL_USE_NEW_IOSTREAMS */
#include <bits/std_iosfwd.h>
#endif /* __STL_USE_NEW_IOSTREAMS */

#include <bits/stl_iterator_base.h>
#include <bits/stl_iterator.h>

// We pick up concept_checks.h from stl_iterator_base.h.

__STL_BEGIN_NAMESPACE

// swap and iter_swap

template <class _ForwardIter1, class _ForwardIter2, class _Tp>
inline void __iter_swap(_ForwardIter1 __a, _ForwardIter2 __b, _Tp*) {
  _Tp __tmp = *__a;
  *__a = *__b;
  *__b = __tmp;
}

template <class _ForwardIter1, class _ForwardIter2>
inline void iter_swap(_ForwardIter1 __a, _ForwardIter2 __b) {
  __STL_REQUIRES(_ForwardIter1, _Mutable_ForwardIterator);
  __STL_REQUIRES(_ForwardIter2, _Mutable_ForwardIterator);
  __STL_CONVERTIBLE(typename iterator_traits<_ForwardIter1>::value_type,
                    typename iterator_traits<_ForwardIter2>::value_type);
  __STL_CONVERTIBLE(typename iterator_traits<_ForwardIter2>::value_type,
                    typename iterator_traits<_ForwardIter1>::value_type);
  __iter_swap(__a, __b, __VALUE_TYPE(__a));
}

template <class _Tp>
inline void swap(_Tp& __a, _Tp& __b) {
  __STL_REQUIRES(_Tp, _Assignable);
  _Tp __tmp = __a;
  __a = __b;
  __b = __tmp;
}

//--------------------------------------------------
// min and max

#if !defined(__BORLANDC__) || __BORLANDC__ >= 0x540 /* C++ Builder 4.0 */

#undef min
#undef max

template <class _Tp>
inline const _Tp& min(const _Tp& __a, const _Tp& __b) {
  __STL_REQUIRES(_Tp, _LessThanComparable);
  //return __b < __a ? __b : __a;
  if (__b < __a) return __b; return __a;
}

template <class _Tp>
inline const _Tp& max(const _Tp& __a, const _Tp& __b) {
  __STL_REQUIRES(_Tp, _LessThanComparable);
  //return  __a < __b ? __b : __a;
  if (__a < __b) return __b; return __a;
}

#endif /* __BORLANDC__ */

template <class _Tp, class _Compare>
inline const _Tp& min(const _Tp& __a, const _Tp& __b, _Compare __comp) {
  //return __comp(__b, __a) ? __b : __a;
  if (__comp(__b, __a)) return __b; return __a;
}

template <class _Tp, class _Compare>
inline const _Tp& max(const _Tp& __a, const _Tp& __b, _Compare __comp) {
  //return __comp(__a, __b) ? __b : __a;
  if (__comp(__a, __b)) return __b; return __a;
}

//--------------------------------------------------
// copy

// All of these auxiliary functions serve two purposes.  (1) Replace
// calls to copy with memmove whenever possible.  (Memmove, not memcpy,
// because the input and output ranges are permitted to overlap.)
// (2) If we're using random access iterators, then write the loop as
// a for loop with an explicit count.

template <class _InputIter, class _OutputIter, class _Distance>
inline _OutputIter __copy(_InputIter __first, _InputIter __last,
                          _OutputIter __result,
                          input_iterator_tag, _Distance*)
{
  for ( ; __first != __last; ++__result, ++__first)
    *__result = *__first;
  return __result;
}

template <class _RandomAccessIter, class _OutputIter, class _Distance>
inline _OutputIter
__copy(_RandomAccessIter __first, _RandomAccessIter __last,
       _OutputIter __result, random_access_iterator_tag, _Distance*)
{
  for (_Distance __n = __last - __first; __n > 0; --__n) {
    *__result = *__first;
    ++__first;
    ++__result;
  }
  return __result;
}

template <class _Tp>
inline _Tp*
__copy_trivial(const _Tp* __first, const _Tp* __last, _Tp* __result) {
  memmove(__result, __first, sizeof(_Tp) * (__last - __first));
  return __result + (__last - __first);
}

#if defined(__STL_FUNCTION_TMPL_PARTIAL_ORDER)

template <class _InputIter, class _OutputIter>
inline _OutputIter __copy_aux2(_InputIter __first, _InputIter __last,
                               _OutputIter __result, __false_type) {
  return __copy(__first, __last, __result,
                __ITERATOR_CATEGORY(__first),
                __DISTANCE_TYPE(__first));
}

template <class _InputIter, class _OutputIter>
inline _OutputIter __copy_aux2(_InputIter __first, _InputIter __last,
                               _OutputIter __result, __true_type) {
  return __copy(__first, __last, __result,
                __ITERATOR_CATEGORY(__first),
                __DISTANCE_TYPE(__first));
}

#ifndef __USLC__

template <class _Tp>
inline _Tp* __copy_aux2(_Tp* __first, _Tp* __last, _Tp* __result,
                        __true_type) {
  return __copy_trivial(__first, __last, __result);
}

#endif /* __USLC__ */

template <class _Tp>
inline _Tp* __copy_aux2(const _Tp* __first, const _Tp* __last, _Tp* __result,
                        __true_type) {
  return __copy_trivial(__first, __last, __result);
}


template <class _InputIter, class _OutputIter, class _Tp>
inline _OutputIter __copy_aux(_InputIter __first, _InputIter __last,
                              _OutputIter __result, _Tp*) {
  typedef typename __type_traits<_Tp>::has_trivial_assignment_operator
          _Trivial;
  return __copy_aux2(__first, __last, __result, _Trivial());
}

template<typename _InputIter, typename _OutputIter>
inline _OutputIter __copy_ni2(_InputIter __first, _InputIter __last,
                               _OutputIter __result, __true_type) {
  return _OutputIter(__copy_aux(__first, __last, __result.base(),
                                __VALUE_TYPE(__first)));
}

template<typename _InputIter, typename _OutputIter>
inline _OutputIter __copy_ni2(_InputIter __first, _InputIter __last,
			      _OutputIter __result, __false_type) {
  return __copy_aux(__first, __last, __result, __VALUE_TYPE(__first));
}

template<typename _InputIter, typename _OutputIter>
inline _OutputIter __copy_ni1(_InputIter __first, _InputIter __last,
                               _OutputIter __result, __true_type) {
  typedef typename _Is_normal_iterator<_OutputIter>::_Normal __Normal;
  return __copy_ni2(__first.base(), __last.base(), __result, __Normal());
}

template<typename _InputIter, typename _OutputIter>
inline _OutputIter __copy_ni1(_InputIter __first, _InputIter __last,
                               _OutputIter __result, __false_type) {
  typedef typename _Is_normal_iterator<_OutputIter>::_Normal __Normal;
  return __copy_ni2(__first, __last, __result, __Normal());
}

template <class _InputIter, class _OutputIter>
inline _OutputIter copy(_InputIter __first, _InputIter __last,
                        _OutputIter __result) {
  __STL_REQUIRES(_InputIter, _InputIterator);
  __STL_REQUIRES(_OutputIter, _OutputIterator);
   typedef typename _Is_normal_iterator<_InputIter>::_Normal __Normal;
   return __copy_ni1(__first, __last, __result, __Normal());
}

// Hack for compilers that don't have partial ordering of function templates
// but do have partial specialization of class templates.
#elif defined(__STL_CLASS_PARTIAL_SPECIALIZATION)

template <class _InputIter, class _OutputIter, class _BoolType>
struct __copy_dispatch {
  static _OutputIter copy(_InputIter __first, _InputIter __last,
                          _OutputIter __result) {
    typedef typename iterator_traits<_InputIter>::iterator_category _Category;
    typedef typename iterator_traits<_InputIter>::difference_type _Distance;
    return __copy(__first, __last, __result, _Category(), (_Distance*) 0);
  }
};

template <class _Tp>
struct __copy_dispatch<_Tp*, _Tp*, __true_type>
{
  static _Tp* copy(const _Tp* __first, const _Tp* __last, _Tp* __result) {
    return __copy_trivial(__first, __last, __result);
  }
};

template <class _Tp>
struct __copy_dispatch<const _Tp*, _Tp*, __true_type>
{
  static _Tp* copy(const _Tp* __first, const _Tp* __last, _Tp* __result) {
    return __copy_trivial(__first, __last, __result);
  }
};

template <class _InputIter, class _OutputIter>
inline _OutputIter copy(_InputIter __first, _InputIter __last,
                        _OutputIter __result) {
  __STL_REQUIRES(_InputIter, _InputIterator);
  __STL_REQUIRES(_OutputIter, _OutputIterator);
  typedef typename iterator_traits<_InputIter>::value_type _Tp;
  typedef typename __type_traits<_Tp>::has_trivial_assignment_operator
          _Trivial;
  return __copy_dispatch<_InputIter, _OutputIter, _Trivial>
    ::copy(__first, __last, __result);
}

// Fallback for compilers with neither partial ordering nor partial
// specialization.  Define the faster version for the basic builtin
// types.
#else /* __STL_CLASS_PARTIAL_SPECIALIZATION */

template <class _InputIter, class _OutputIter>
inline _OutputIter copy(_InputIter __first, _InputIter __last,
                        _OutputIter __result)
{
  return __copy(__first, __last, __result,
                __ITERATOR_CATEGORY(__first),
                __DISTANCE_TYPE(__first));
}

#define __SGI_STL_DECLARE_COPY_TRIVIAL(_Tp)                                \
  inline _Tp* copy(const _Tp* __first, const _Tp* __last, _Tp* __result) { \
    memmove(__result, __first, sizeof(_Tp) * (__last - __first));          \
    return __result + (__last - __first);                                  \
  }

__SGI_STL_DECLARE_COPY_TRIVIAL(char)
__SGI_STL_DECLARE_COPY_TRIVIAL(signed char)
__SGI_STL_DECLARE_COPY_TRIVIAL(unsigned char)
__SGI_STL_DECLARE_COPY_TRIVIAL(short)
__SGI_STL_DECLARE_COPY_TRIVIAL(unsigned short)
__SGI_STL_DECLARE_COPY_TRIVIAL(int)
__SGI_STL_DECLARE_COPY_TRIVIAL(unsigned int)
__SGI_STL_DECLARE_COPY_TRIVIAL(long)
__SGI_STL_DECLARE_COPY_TRIVIAL(unsigned long)
#ifdef __STL_HAS_WCHAR_T
__SGI_STL_DECLARE_COPY_TRIVIAL(wchar_t)
#endif
#ifdef _STL_LONG_LONG
__SGI_STL_DECLARE_COPY_TRIVIAL(long long)
__SGI_STL_DECLARE_COPY_TRIVIAL(unsigned long long)
#endif 
__SGI_STL_DECLARE_COPY_TRIVIAL(float)
__SGI_STL_DECLARE_COPY_TRIVIAL(double)
__SGI_STL_DECLARE_COPY_TRIVIAL(long double)

#undef __SGI_STL_DECLARE_COPY_TRIVIAL
#endif /* __STL_CLASS_PARTIAL_SPECIALIZATION */

//--------------------------------------------------
// copy_backward

template <class _BidirectionalIter1, class _BidirectionalIter2, 
          class _Distance>
inline _BidirectionalIter2 __copy_backward(_BidirectionalIter1 __first, 
                                           _BidirectionalIter1 __last, 
                                           _BidirectionalIter2 __result,
                                           bidirectional_iterator_tag,
                                           _Distance*)
{
  while (__first != __last)
    *--__result = *--__last;
  return __result;
}

template <class _RandomAccessIter, class _BidirectionalIter, class _Distance>
inline _BidirectionalIter __copy_backward(_RandomAccessIter __first, 
                                          _RandomAccessIter __last, 
                                          _BidirectionalIter __result,
                                          random_access_iterator_tag,
                                          _Distance*)
{
  for (_Distance __n = __last - __first; __n > 0; --__n)
    *--__result = *--__last;
  return __result;
}

#ifdef __STL_CLASS_PARTIAL_SPECIALIZATION 

// This dispatch class is a workaround for compilers that do not 
// have partial ordering of function templates.  All we're doing is
// creating a specialization so that we can turn a call to copy_backward
// into a memmove whenever possible.

template <class _BidirectionalIter1, class _BidirectionalIter2,
          class _BoolType>
struct __copy_backward_dispatch
{
  typedef typename iterator_traits<_BidirectionalIter1>::iterator_category 
          _Cat;
  typedef typename iterator_traits<_BidirectionalIter1>::difference_type
          _Distance;

  static _BidirectionalIter2 copy(_BidirectionalIter1 __first, 
                                  _BidirectionalIter1 __last, 
                                  _BidirectionalIter2 __result) {
    return __copy_backward(__first, __last, __result, _Cat(), (_Distance*) 0);
  }
};

template <class _Tp>
struct __copy_backward_dispatch<_Tp*, _Tp*, __true_type>
{
  static _Tp* copy(const _Tp* __first, const _Tp* __last, _Tp* __result) {
    const ptrdiff_t _Num = __last - __first;
    memmove(__result - _Num, __first, sizeof(_Tp) * _Num);
    return __result - _Num;
  }
};

template <class _Tp>
struct __copy_backward_dispatch<const _Tp*, _Tp*, __true_type>
{
  static _Tp* copy(const _Tp* __first, const _Tp* __last, _Tp* __result) {
    return  __copy_backward_dispatch<_Tp*, _Tp*, __true_type>
      ::copy(__first, __last, __result);
  }
};

template <class _BI1, class _BI2>
inline _BI2 __copy_backward_aux(_BI1 __first, _BI1 __last, _BI2 __result) {
  typedef typename __type_traits<typename iterator_traits<_BI2>::value_type>
                        ::has_trivial_assignment_operator
          _Trivial;
  return __copy_backward_dispatch<_BI1, _BI2, _Trivial>
              ::copy(__first, __last, __result);
}

template <typename _BI1, typename _BI2>
inline _BI2 __copy_backward_output_normal_iterator(_BI1 __first, _BI1 __last,
                                                   _BI2 __result, __true_type) {
  return _BI2(__copy_backward_aux(__first, __last, __result.base()));
}

template <typename _BI1, typename _BI2>
inline _BI2 __copy_backward_output_normal_iterator(_BI1 __first, _BI1 __last,
                                                   _BI2 __result, __false_type){
  return __copy_backward_aux(__first, __last, __result);
}

template <typename _BI1, typename _BI2>
inline _BI2 __copy_backward_input_normal_iterator(_BI1 __first, _BI1 __last,
                                                  _BI2 __result, __true_type) {
  typedef typename _Is_normal_iterator<_BI2>::_Normal __Normal;
  return __copy_backward_output_normal_iterator(__first.base(), __last.base(),
                                                __result, __Normal());
}

template <typename _BI1, typename _BI2>
inline _BI2 __copy_backward_input_normal_iterator(_BI1 __first, _BI1 __last,
                                                  _BI2 __result, __false_type) {
  typedef typename _Is_normal_iterator<_BI2>::_Normal __Normal;
  return __copy_backward_output_normal_iterator(__first, __last, __result,
                                                __Normal());
}

template <typename _BI1, typename _BI2>
inline _BI2 copy_backward(_BI1 __first, _BI1 __last, _BI2 __result) {
  __STL_REQUIRES(_BI1, _BidirectionalIterator);
  __STL_REQUIRES(_BI2, _Mutable_BidirectionalIterator);
  __STL_CONVERTIBLE(typename iterator_traits<_BI1>::value_type,
                    typename iterator_traits<_BI2>::value_type);
  typedef typename _Is_normal_iterator<_BI1>::_Normal __Normal;
  return __copy_backward_input_normal_iterator(__first, __last, __result,
                                               __Normal());
}

#else /* __STL_CLASS_PARTIAL_SPECIALIZATION */

template <class _BI1, class _BI2>
inline _BI2 copy_backward(_BI1 __first, _BI1 __last, _BI2 __result) {
  return __copy_backward(__first, __last, __result,
                         __ITERATOR_CATEGORY(__first),
                         __DISTANCE_TYPE(__first));
}

#endif /* __STL_CLASS_PARTIAL_SPECIALIZATION */

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

template <class _InputIter, class _Size, class _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 <class _RAIter, class _Size, class _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, copy(__first, __last, __result));
}

template <class _InputIter, class _Size, class _OutputIter>
inline pair<_InputIter, _OutputIter>
__copy_n(_InputIter __first, _Size __count, _OutputIter __result) {
  return __copy_n(__first, __count, __result,
                  __ITERATOR_CATEGORY(__first));
}

template <class _InputIter, class _Size, class _OutputIter>
inline pair<_InputIter, _OutputIter>
copy_n(_InputIter __first, _Size __count, _OutputIter __result) {
  __STL_REQUIRES(_InputIter, _InputIterator);
  __STL_REQUIRES(_OutputIter, _OutputIterator);
  return __copy_n(__first, __count, __result);
}

//--------------------------------------------------
// fill and fill_n


template <class _ForwardIter, class _Tp>
void fill(_ForwardIter __first, _ForwardIter __last, const _Tp& __value) {
  __STL_REQUIRES(_ForwardIter, _Mutable_ForwardIterator);
  for ( ; __first != __last; ++__first)
    *__first = __value;
}

template <class _OutputIter, class _Size, class _Tp>
_OutputIter fill_n(_OutputIter __first, _Size __n, const _Tp& __value) {
  __STL_REQUIRES(_OutputIter, _OutputIterator);
  for ( ; __n > 0; --__n, ++__first)
    *__first = __value;
  return __first;
}

// Specialization: for one-byte types we can use memset.

inline void fill(unsigned char* __first, unsigned char* __last,
                 const unsigned char& __c) {
  unsigned char __tmp = __c;
  memset(__first, __tmp, __last - __first);
}

inline void fill(signed char* __first, signed char* __last,
                 const signed char& __c) {
  signed char __tmp = __c;
  memset(__first, static_cast<unsigned char>(__tmp), __last - __first);
}

inline void fill(char* __first, char* __last, const char& __c) {
  char __tmp = __c;
  memset(__first, static_cast<unsigned char>(__tmp), __last - __first);
}

#ifdef __STL_FUNCTION_TMPL_PARTIAL_ORDER

template <class _Size>
inline unsigned char* fill_n(unsigned char* __first, _Size __n,
                             const unsigned char& __c) {
  fill(__first, __first + __n, __c);
  return __first + __n;
}

template <class _Size>
inline signed char* fill_n(char* __first, _Size __n,
                           const signed char& __c) {
  fill(__first, __first + __n, __c);
  return __first + __n;
}

template <class _Size>
inline char* fill_n(char* __first, _Size __n, const char& __c) {
  fill(__first, __first + __n, __c);
  return __first + __n;
}

#endif /* __STL_FUNCTION_TMPL_PARTIAL_ORDER */

//--------------------------------------------------
// equal and mismatch

template <class _InputIter1, class _InputIter2>
pair<_InputIter1, _InputIter2> mismatch(_InputIter1 __first1,
                                        _InputIter1 __last1,
                                        _InputIter2 __first2) {
  __STL_REQUIRES(_InputIter1, _InputIterator);
  __STL_REQUIRES(_InputIter2, _InputIterator);
  __STL_REQUIRES(typename iterator_traits<_InputIter1>::value_type,
                 _EqualityComparable);
  __STL_REQUIRES(typename iterator_traits<_InputIter2>::value_type,
                 _EqualityComparable);
  while (__first1 != __last1 && *__first1 == *__first2) {
    ++__first1;
    ++__first2;
  }
  return pair<_InputIter1, _InputIter2>(__first1, __first2);
}

template <class _InputIter1, class _InputIter2, class _BinaryPredicate>
pair<_InputIter1, _InputIter2> mismatch(_InputIter1 __first1,
                                        _InputIter1 __last1,
                                        _InputIter2 __first2,
                                        _BinaryPredicate __binary_pred) {
  __STL_REQUIRES(_InputIter1, _InputIterator);
  __STL_REQUIRES(_InputIter2, _InputIterator);
  while (__first1 != __last1 && __binary_pred(*__first1, *__first2)) {
    ++__first1;
    ++__first2;
  }
  return pair<_InputIter1, _InputIter2>(__first1, __first2);
}

template <class _InputIter1, class _InputIter2>
inline bool equal(_InputIter1 __first1, _InputIter1 __last1,
                  _InputIter2 __first2) {
  __STL_REQUIRES(_InputIter1, _InputIterator);
  __STL_REQUIRES(_InputIter2, _InputIterator);
  __STL_REQUIRES(typename iterator_traits<_InputIter1>::value_type,
                 _EqualityComparable);
  __STL_REQUIRES(typename iterator_traits<_InputIter2>::value_type,
                 _EqualityComparable);
  for ( ; __first1 != __last1; ++__first1, ++__first2)
    if (*__first1 != *__first2)
      return false;
  return true;
}

template <class _InputIter1, class _InputIter2, class _BinaryPredicate>
inline bool equal(_InputIter1 __first1, _InputIter1 __last1,
                  _InputIter2 __first2, _BinaryPredicate __binary_pred) {
  __STL_REQUIRES(_InputIter1, _InputIterator);
  __STL_REQUIRES(_InputIter2, _InputIterator);
  for ( ; __first1 != __last1; ++__first1, ++__first2)
    if (!__binary_pred(*__first1, *__first2))
      return false;
  return true;
}

//--------------------------------------------------
// lexicographical_compare and lexicographical_compare_3way.
// (the latter is not part of the C++ standard.)

template <class _InputIter1, class _InputIter2>
bool lexicographical_compare(_InputIter1 __first1, _InputIter1 __last1,
                             _InputIter2 __first2, _InputIter2 __last2) {
  __STL_REQUIRES(_InputIter1, _InputIterator);
  __STL_REQUIRES(_InputIter2, _InputIterator);
  __STL_REQUIRES(typename iterator_traits<_InputIter1>::value_type,
                 _LessThanComparable);
  __STL_REQUIRES(typename iterator_traits<_InputIter2>::value_type,
                 _LessThanComparable);
  for ( ; __first1 != __last1 && __first2 != __last2
        ; ++__first1, ++__first2) {
    if (*__first1 < *__first2)
      return true;
    if (*__first2 < *__first1)
      return false;
  }
  return __first1 == __last1 && __first2 != __last2;
}

template <class _InputIter1, class _InputIter2, class _Compare>
bool lexicographical_compare(_InputIter1 __first1, _InputIter1 __last1,
                             _InputIter2 __first2, _InputIter2 __last2,
                             _Compare __comp) {
  __STL_REQUIRES(_InputIter1, _InputIterator);
  __STL_REQUIRES(_InputIter2, _InputIterator);
  for ( ; __first1 != __last1 && __first2 != __last2
        ; ++__first1, ++__first2) {
    if (__comp(*__first1, *__first2))
      return true;
    if (__comp(*__first2, *__first1))
      return false;
  }
  return __first1 == __last1 && __first2 != __last2;
}

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

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

template <class _InputIter1, class _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 = 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
}

template <class _InputIter1, class _InputIter2>
int lexicographical_compare_3way(_InputIter1 __first1, _InputIter1 __last1,
                                 _InputIter2 __first2, _InputIter2 __last2)
{
  __STL_REQUIRES(_InputIter1, _InputIterator);
  __STL_REQUIRES(_InputIter2, _InputIterator);
  __STL_REQUIRES(typename iterator_traits<_InputIter1>::value_type,
                 _LessThanComparable);
  __STL_REQUIRES(typename iterator_traits<_InputIter2>::value_type,
                 _LessThanComparable);
  return __lexicographical_compare_3way(__first1, __last1, __first2, __last2);
}

__STL_END_NAMESPACE

#endif /* __SGI_STL_INTERNAL_ALGOBASE_H */

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