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

   1 // Core algorithmic facilities -*- C++ -*-
   2
   3 // Copyright (C) 2001-2013 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 /*
  26  *
  27  * Copyright (c) 1994
  28  * Hewlett-Packard Company
  29  *
  30  * Permission to use, copy, modify, distribute and sell this software
  31  * and its documentation for any purpose is hereby granted without fee,
  32  * provided that the above copyright notice appear in all copies and
  33  * that both that copyright notice and this permission notice appear
  34  * in supporting documentation.  Hewlett-Packard Company makes no
  35  * representations about the suitability of this software for any
  36  * purpose.  It is provided "as is" without express or implied warranty.
  37  *
  38  *
  39  * Copyright (c) 1996-1998
  40  * Silicon Graphics Computer Systems, Inc.
  41  *
  42  * Permission to use, copy, modify, distribute and sell this software
  43  * and its documentation for any purpose is hereby granted without fee,
  44  * provided that the above copyright notice appear in all copies and
  45  * that both that copyright notice and this permission notice appear
  46  * in supporting documentation.  Silicon Graphics makes no
  47  * representations about the suitability of this software for any
  48  * purpose.  It is provided "as is" without express or implied warranty.
  49  */
  50
  51 /** @file bits/stl_algobase.h
  52  *  This is an internal header file, included by other library headers.
  53  *  Do not attempt to use it directly. @headername{algorithm}
  54  */
  55
  56 #ifndef _STL_ALGOBASE_H
  57 #define _STL_ALGOBASE_H 1
  58
  59 #include <bits/c++config.h>
  60 #include <bits/functexcept.h>
  61 #include <bits/cpp_type_traits.h>
  62 #include <ext/type_traits.h>
  63 #include <ext/numeric_traits.h>
  64 #include <bits/stl_pair.h>
  65 #include <bits/stl_iterator_base_types.h>
  66 #include <bits/stl_iterator_base_funcs.h>
  67 #include <bits/stl_iterator.h>
  68 #include <bits/concept_check.h>
  69 #include <debug/debug.h>
  70 #include <bits/move.h> // For std::swap and _GLIBCXX_MOVE
  71
  72 namespace std _GLIBCXX_VISIBILITY(default)
  73 {
  74 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  75
  76 #if __cplusplus < 201103L
  77   // See http://gcc.gnu.org/ml/libstdc++/2004-08/msg00167.html: in a
  78   // nutshell, we are partially implementing the resolution of DR 187,
  79   // when it's safe, i.e., the value_types are equal.
  80   template<bool _BoolType>
  81     struct __iter_swap
  82     {
  83       template<typename _ForwardIterator1, typename _ForwardIterator2>
  84         static void
  85         iter_swap(_ForwardIterator1 __a, _ForwardIterator2 __b)
  86         {
  87           typedef typename iterator_traits<_ForwardIterator1>::value_type
  88             _ValueType1;
  89           _ValueType1 __tmp = _GLIBCXX_MOVE(*__a);
  90           *__a = _GLIBCXX_MOVE(*__b);
  91           *__b = _GLIBCXX_MOVE(__tmp);
  92         }
  93     };
  94
  95   template<>
  96     struct __iter_swap<true>
  97     {
  98       template<typename _ForwardIterator1, typename _ForwardIterator2>
  99         static void
 100         iter_swap(_ForwardIterator1 __a, _ForwardIterator2 __b)
 101         {
 102           swap(*__a, *__b);
 103         }
 104     };
 105 #endif
 106
 107   /**
 108    *  @brief Swaps the contents of two iterators.
 109    *  @ingroup mutating_algorithms
 110    *  @param  __a  An iterator.
 111    *  @param  __b  Another iterator.
 112    *  @return   Nothing.
 113    *
 114    *  This function swaps the values pointed to by two iterators, not the
 115    *  iterators themselves.
 116   */
 117   template<typename _ForwardIterator1, typename _ForwardIterator2>
 118     inline void
 119     iter_swap(_ForwardIterator1 __a, _ForwardIterator2 __b)
 120     {
 121       // concept requirements
 122       __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
 123                                   _ForwardIterator1>)
 124       __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
 125                                   _ForwardIterator2>)
 126
 127 #if __cplusplus < 201103L
 128       typedef typename iterator_traits<_ForwardIterator1>::value_type
 129         _ValueType1;
 130       typedef typename iterator_traits<_ForwardIterator2>::value_type
 131         _ValueType2;
 132
 133       __glibcxx_function_requires(_ConvertibleConcept<_ValueType1,
 134                                   _ValueType2>)
 135       __glibcxx_function_requires(_ConvertibleConcept<_ValueType2,
 136                                   _ValueType1>)
 137
 138       typedef typename iterator_traits<_ForwardIterator1>::reference
 139         _ReferenceType1;
 140       typedef typename iterator_traits<_ForwardIterator2>::reference
 141         _ReferenceType2;
 142       std::__iter_swap<__are_same<_ValueType1, _ValueType2>::__value
 143         && __are_same<_ValueType1&, _ReferenceType1>::__value
 144         && __are_same<_ValueType2&, _ReferenceType2>::__value>::
 145         iter_swap(__a, __b);
 146 #else
 147       swap(*__a, *__b);
 148 #endif
 149     }
 150
 151   /**
 152    *  @brief Swap the elements of two sequences.
 153    *  @ingroup mutating_algorithms
 154    *  @param  __first1  A forward iterator.
 155    *  @param  __last1   A forward iterator.
 156    *  @param  __first2  A forward iterator.
 157    *  @return   An iterator equal to @p first2+(last1-first1).
 158    *
 159    *  Swaps each element in the range @p [first1,last1) with the
 160    *  corresponding element in the range @p [first2,(last1-first1)).
 161    *  The ranges must not overlap.
 162   */
 163   template<typename _ForwardIterator1, typename _ForwardIterator2>
 164     _ForwardIterator2
 165     swap_ranges(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
 166                 _ForwardIterator2 __first2)
 167     {
 168       // concept requirements
 169       __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
 170                                   _ForwardIterator1>)
 171       __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
 172                                   _ForwardIterator2>)
 173       __glibcxx_requires_valid_range(__first1, __last1);
 174
 175       for (; __first1 != __last1; ++__first1, ++__first2)
 176         std::iter_swap(__first1, __first2);
 177       return __first2;
 178     }
 179
 180   /**
 181    *  @brief This does what you think it does.
 182    *  @ingroup sorting_algorithms
 183    *  @param  __a  A thing of arbitrary type.
 184    *  @param  __b  Another thing of arbitrary type.
 185    *  @return   The lesser of the parameters.
 186    *
 187    *  This is the simple classic generic implementation.  It will work on
 188    *  temporary expressions, since they are only evaluated once, unlike a
 189    *  preprocessor macro.
 190   */
 191   template<typename _Tp>
 192     inline const _Tp&
 193     min(const _Tp& __a, const _Tp& __b)
 194     {
 195       // concept requirements
 196       __glibcxx_function_requires(_LessThanComparableConcept<_Tp>)
 197       //return __b < __a ? __b : __a;
 198       if (__b < __a)
 199         return __b;
 200       return __a;
 201     }
 202
 203   /**
 204    *  @brief This does what you think it does.
 205    *  @ingroup sorting_algorithms
 206    *  @param  __a  A thing of arbitrary type.
 207    *  @param  __b  Another thing of arbitrary type.
 208    *  @return   The greater of the parameters.
 209    *
 210    *  This is the simple classic generic implementation.  It will work on
 211    *  temporary expressions, since they are only evaluated once, unlike a
 212    *  preprocessor macro.
 213   */
 214   template<typename _Tp>
 215     inline const _Tp&
 216     max(const _Tp& __a, const _Tp& __b)
 217     {
 218       // concept requirements
 219       __glibcxx_function_requires(_LessThanComparableConcept<_Tp>)
 220       //return  __a < __b ? __b : __a;
 221       if (__a < __b)
 222         return __b;
 223       return __a;
 224     }
 225
 226   /**
 227    *  @brief This does what you think it does.
 228    *  @ingroup sorting_algorithms
 229    *  @param  __a  A thing of arbitrary type.
 230    *  @param  __b  Another thing of arbitrary type.
 231    *  @param  __comp  A @link comparison_functors comparison functor@endlink.
 232    *  @return   The lesser of the parameters.
 233    *
 234    *  This will work on temporary expressions, since they are only evaluated
 235    *  once, unlike a preprocessor macro.
 236   */
 237   template<typename _Tp, typename _Compare>
 238     inline const _Tp&
 239     min(const _Tp& __a, const _Tp& __b, _Compare __comp)
 240     {
 241       //return __comp(__b, __a) ? __b : __a;
 242       if (__comp(__b, __a))
 243         return __b;
 244       return __a;
 245     }
 246
 247   /**
 248    *  @brief This does what you think it does.
 249    *  @ingroup sorting_algorithms
 250    *  @param  __a  A thing of arbitrary type.
 251    *  @param  __b  Another thing of arbitrary type.
 252    *  @param  __comp  A @link comparison_functors comparison functor@endlink.
 253    *  @return   The greater of the parameters.
 254    *
 255    *  This will work on temporary expressions, since they are only evaluated
 256    *  once, unlike a preprocessor macro.
 257   */
 258   template<typename _Tp, typename _Compare>
 259     inline const _Tp&
 260     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
 261     {
 262       //return __comp(__a, __b) ? __b : __a;
 263       if (__comp(__a, __b))
 264         return __b;
 265       return __a;
 266     }
 267
 268   // If _Iterator is a __normal_iterator return its base (a plain pointer,
 269   // normally) otherwise return it untouched.  See copy, fill, ...
 270   template<typename _Iterator>
 271     struct _Niter_base
 272     : _Iter_base<_Iterator, __is_normal_iterator<_Iterator>::__value>
 273     { };
 274
 275   template<typename _Iterator>
 276     inline typename _Niter_base<_Iterator>::iterator_type
 277     __niter_base(_Iterator __it)
 278     { return std::_Niter_base<_Iterator>::_S_base(__it); }
 279
 280   // Likewise, for move_iterator.
 281   template<typename _Iterator>
 282     struct _Miter_base
 283     : _Iter_base<_Iterator, __is_move_iterator<_Iterator>::__value>
 284     { };
 285
 286   template<typename _Iterator>
 287     inline typename _Miter_base<_Iterator>::iterator_type
 288     __miter_base(_Iterator __it)
 289     { return std::_Miter_base<_Iterator>::_S_base(__it); }
 290
 291   // All of these auxiliary structs serve two purposes.  (1) Replace
 292   // calls to copy with memmove whenever possible.  (Memmove, not memcpy,
 293   // because the input and output ranges are permitted to overlap.)
 294   // (2) If we're using random access iterators, then write the loop as
 295   // a for loop with an explicit count.
 296
 297   template<bool, bool, typename>
 298     struct __copy_move
 299     {
 300       template<typename _II, typename _OI>
 301         static _OI
 302         __copy_m(_II __first, _II __last, _OI __result)
 303         {
 304           for (; __first != __last; ++__result, ++__first)
 305             *__result = *__first;
 306           return __result;
 307         }
 308     };
 309
 310 #if __cplusplus >= 201103L
 311   template<typename _Category>
 312     struct __copy_move<true, false, _Category>
 313     {
 314       template<typename _II, typename _OI>
 315         static _OI
 316         __copy_m(_II __first, _II __last, _OI __result)
 317         {
 318           for (; __first != __last; ++__result, ++__first)
 319             *__result = std::move(*__first);
 320           return __result;
 321         }
 322     };
 323 #endif
 324
 325   template<>
 326     struct __copy_move<false, false, random_access_iterator_tag>
 327     {
 328       template<typename _II, typename _OI>
 329         static _OI
 330         __copy_m(_II __first, _II __last, _OI __result)
 331         {
 332           typedef typename iterator_traits<_II>::difference_type _Distance;
 333           for(_Distance __n = __last - __first; __n > 0; --__n)
 334             {
 335               *__result = *__first;
 336               ++__first;
 337               ++__result;
 338             }
 339           return __result;
 340         }
 341     };
 342
 343 #if __cplusplus >= 201103L
 344   template<>
 345     struct __copy_move<true, false, random_access_iterator_tag>
 346     {
 347       template<typename _II, typename _OI>
 348         static _OI
 349         __copy_m(_II __first, _II __last, _OI __result)
 350         {
 351           typedef typename iterator_traits<_II>::difference_type _Distance;
 352           for(_Distance __n = __last - __first; __n > 0; --__n)
 353             {
 354               *__result = std::move(*__first);
 355               ++__first;
 356               ++__result;
 357             }
 358           return __result;
 359         }
 360     };
 361 #endif
 362
 363   template<bool _IsMove>
 364     struct __copy_move<_IsMove, true, random_access_iterator_tag>
 365     {
 366       template<typename _Tp>
 367         static _Tp*
 368         __copy_m(const _Tp* __first, const _Tp* __last, _Tp* __result)
 369         {
 370           const ptrdiff_t _Num = __last - __first;
 371           if (_Num)
 372             __builtin_memmove(__result, __first, sizeof(_Tp) * _Num);
 373           return __result + _Num;
 374         }
 375     };
 376
 377   template<bool _IsMove, typename _II, typename _OI>
 378     inline _OI
 379     __copy_move_a(_II __first, _II __last, _OI __result)
 380     {
 381       typedef typename iterator_traits<_II>::value_type _ValueTypeI;
 382       typedef typename iterator_traits<_OI>::value_type _ValueTypeO;
 383       typedef typename iterator_traits<_II>::iterator_category _Category;
 384       const bool __simple = (__is_trivial(_ValueTypeI)
 385                              && __is_pointer<_II>::__value
 386                              && __is_pointer<_OI>::__value
 387                              && __are_same<_ValueTypeI, _ValueTypeO>::__value);
 388
 389       return std::__copy_move<_IsMove, __simple,
 390                               _Category>::__copy_m(__first, __last, __result);
 391     }
 392
 393   // Helpers for streambuf iterators (either istream or ostream).
 394   // NB: avoid including <iosfwd>, relatively large.
 395   template<typename _CharT>
 396     struct char_traits;
 397
 398   template<typename _CharT, typename _Traits>
 399     class istreambuf_iterator;
 400
 401   template<typename _CharT, typename _Traits>
 402     class ostreambuf_iterator;
 403
 404   template<bool _IsMove, typename _CharT>
 405     typename __gnu_cxx::__enable_if<__is_char<_CharT>::__value,
 406              ostreambuf_iterator<_CharT, char_traits<_CharT> > >::__type
 407     __copy_move_a2(_CharT*, _CharT*,
 408                    ostreambuf_iterator<_CharT, char_traits<_CharT> >);
 409
 410   template<bool _IsMove, typename _CharT>
 411     typename __gnu_cxx::__enable_if<__is_char<_CharT>::__value,
 412              ostreambuf_iterator<_CharT, char_traits<_CharT> > >::__type
 413     __copy_move_a2(const _CharT*, const _CharT*,
 414                    ostreambuf_iterator<_CharT, char_traits<_CharT> >);
 415
 416   template<bool _IsMove, typename _CharT>
 417     typename __gnu_cxx::__enable_if<__is_char<_CharT>::__value,
 418                                     _CharT*>::__type
 419     __copy_move_a2(istreambuf_iterator<_CharT, char_traits<_CharT> >,
 420                    istreambuf_iterator<_CharT, char_traits<_CharT> >, _CharT*);
 421
 422   template<bool _IsMove, typename _II, typename _OI>
 423     inline _OI
 424     __copy_move_a2(_II __first, _II __last, _OI __result)
 425     {
 426       return _OI(std::__copy_move_a<_IsMove>(std::__niter_base(__first),
 427                                              std::__niter_base(__last),
 428                                              std::__niter_base(__result)));
 429     }
 430
 431   /**
 432    *  @brief Copies the range [first,last) into result.
 433    *  @ingroup mutating_algorithms
 434    *  @param  __first  An input iterator.
 435    *  @param  __last   An input iterator.
 436    *  @param  __result An output iterator.
 437    *  @return   result + (first - last)
 438    *
 439    *  This inline function will boil down to a call to @c memmove whenever
 440    *  possible.  Failing that, if random access iterators are passed, then the
 441    *  loop count will be known (and therefore a candidate for compiler
 442    *  optimizations such as unrolling).  Result may not be contained within
 443    *  [first,last); the copy_backward function should be used instead.
 444    *
 445    *  Note that the end of the output range is permitted to be contained
 446    *  within [first,last).
 447   */
 448   template<typename _II, typename _OI>
 449     inline _OI
 450     copy(_II __first, _II __last, _OI __result)
 451     {
 452       // concept requirements
 453       __glibcxx_function_requires(_InputIteratorConcept<_II>)
 454       __glibcxx_function_requires(_OutputIteratorConcept<_OI,
 455             typename iterator_traits<_II>::value_type>)
 456       __glibcxx_requires_valid_range(__first, __last);
 457
 458       return (std::__copy_move_a2<__is_move_iterator<_II>::__value>
 459               (std::__miter_base(__first), std::__miter_base(__last),
 460                __result));
 461     }
 462
 463 #if __cplusplus >= 201103L
 464   /**
 465    *  @brief Moves the range [first,last) into result.
 466    *  @ingroup mutating_algorithms
 467    *  @param  __first  An input iterator.
 468    *  @param  __last   An input iterator.
 469    *  @param  __result An output iterator.
 470    *  @return   result + (first - last)
 471    *
 472    *  This inline function will boil down to a call to @c memmove whenever
 473    *  possible.  Failing that, if random access iterators are passed, then the
 474    *  loop count will be known (and therefore a candidate for compiler
 475    *  optimizations such as unrolling).  Result may not be contained within
 476    *  [first,last); the move_backward function should be used instead.
 477    *
 478    *  Note that the end of the output range is permitted to be contained
 479    *  within [first,last).
 480   */
 481   template<typename _II, typename _OI>
 482     inline _OI
 483     move(_II __first, _II __last, _OI __result)
 484     {
 485       // concept requirements
 486       __glibcxx_function_requires(_InputIteratorConcept<_II>)
 487       __glibcxx_function_requires(_OutputIteratorConcept<_OI,
 488             typename iterator_traits<_II>::value_type>)
 489       __glibcxx_requires_valid_range(__first, __last);
 490
 491       return std::__copy_move_a2<true>(std::__miter_base(__first),
 492                                        std::__miter_base(__last), __result);
 493     }
 494
 495 #define _GLIBCXX_MOVE3(_Tp, _Up, _Vp) std::move(_Tp, _Up, _Vp)
 496 #else
 497 #define _GLIBCXX_MOVE3(_Tp, _Up, _Vp) std::copy(_Tp, _Up, _Vp)
 498 #endif
 499
 500   template<bool, bool, typename>
 501     struct __copy_move_backward
 502     {
 503       template<typename _BI1, typename _BI2>
 504         static _BI2
 505         __copy_move_b(_BI1 __first, _BI1 __last, _BI2 __result)
 506         {
 507           while (__first != __last)
 508             *--__result = *--__last;
 509           return __result;
 510         }
 511     };
 512
 513 #if __cplusplus >= 201103L
 514   template<typename _Category>
 515     struct __copy_move_backward<true, false, _Category>
 516     {
 517       template<typename _BI1, typename _BI2>
 518         static _BI2
 519         __copy_move_b(_BI1 __first, _BI1 __last, _BI2 __result)
 520         {
 521           while (__first != __last)
 522             *--__result = std::move(*--__last);
 523           return __result;
 524         }
 525     };
 526 #endif
 527
 528   template<>
 529     struct __copy_move_backward<false, false, random_access_iterator_tag>
 530     {
 531       template<typename _BI1, typename _BI2>
 532         static _BI2
 533         __copy_move_b(_BI1 __first, _BI1 __last, _BI2 __result)
 534         {
 535           typename iterator_traits<_BI1>::difference_type __n;
 536           for (__n = __last - __first; __n > 0; --__n)
 537             *--__result = *--__last;
 538           return __result;
 539         }
 540     };
 541
 542 #if __cplusplus >= 201103L
 543   template<>
 544     struct __copy_move_backward<true, false, random_access_iterator_tag>
 545     {
 546       template<typename _BI1, typename _BI2>
 547         static _BI2
 548         __copy_move_b(_BI1 __first, _BI1 __last, _BI2 __result)
 549         {
 550           typename iterator_traits<_BI1>::difference_type __n;
 551           for (__n = __last - __first; __n > 0; --__n)
 552             *--__result = std::move(*--__last);
 553           return __result;
 554         }
 555     };
 556 #endif
 557
 558   template<bool _IsMove>
 559     struct __copy_move_backward<_IsMove, true, random_access_iterator_tag>
 560     {
 561       template<typename _Tp>
 562         static _Tp*
 563         __copy_move_b(const _Tp* __first, const _Tp* __last, _Tp* __result)
 564         {
 565           const ptrdiff_t _Num = __last - __first;
 566           if (_Num)
 567             __builtin_memmove(__result - _Num, __first, sizeof(_Tp) * _Num);
 568           return __result - _Num;
 569         }
 570     };
 571
 572   template<bool _IsMove, typename _BI1, typename _BI2>
 573     inline _BI2
 574     __copy_move_backward_a(_BI1 __first, _BI1 __last, _BI2 __result)
 575     {
 576       typedef typename iterator_traits<_BI1>::value_type _ValueType1;
 577       typedef typename iterator_traits<_BI2>::value_type _ValueType2;
 578       typedef typename iterator_traits<_BI1>::iterator_category _Category;
 579       const bool __simple = (__is_trivial(_ValueType1)
 580                              && __is_pointer<_BI1>::__value
 581                              && __is_pointer<_BI2>::__value
 582                              && __are_same<_ValueType1, _ValueType2>::__value);
 583
 584       return std::__copy_move_backward<_IsMove, __simple,
 585                                        _Category>::__copy_move_b(__first,
 586                                                                  __last,
 587                                                                  __result);
 588     }
 589
 590   template<bool _IsMove, typename _BI1, typename _BI2>
 591     inline _BI2
 592     __copy_move_backward_a2(_BI1 __first, _BI1 __last, _BI2 __result)
 593     {
 594       return _BI2(std::__copy_move_backward_a<_IsMove>
 595                   (std::__niter_base(__first), std::__niter_base(__last),
 596                    std::__niter_base(__result)));
 597     }
 598
 599   /**
 600    *  @brief Copies the range [first,last) into result.
 601    *  @ingroup mutating_algorithms
 602    *  @param  __first  A bidirectional iterator.
 603    *  @param  __last   A bidirectional iterator.
 604    *  @param  __result A bidirectional iterator.
 605    *  @return   result - (first - last)
 606    *
 607    *  The function has the same effect as copy, but starts at the end of the
 608    *  range and works its way to the start, returning the start of the result.
 609    *  This inline function will boil down to a call to @c memmove whenever
 610    *  possible.  Failing that, if random access iterators are passed, then the
 611    *  loop count will be known (and therefore a candidate for compiler
 612    *  optimizations such as unrolling).
 613    *
 614    *  Result may not be in the range (first,last].  Use copy instead.  Note
 615    *  that the start of the output range may overlap [first,last).
 616   */
 617   template<typename _BI1, typename _BI2>
 618     inline _BI2
 619     copy_backward(_BI1 __first, _BI1 __last, _BI2 __result)
 620     {
 621       // concept requirements
 622       __glibcxx_function_requires(_BidirectionalIteratorConcept<_BI1>)
 623       __glibcxx_function_requires(_Mutable_BidirectionalIteratorConcept<_BI2>)
 624       __glibcxx_function_requires(_ConvertibleConcept<
 625             typename iterator_traits<_BI1>::value_type,
 626             typename iterator_traits<_BI2>::value_type>)
 627       __glibcxx_requires_valid_range(__first, __last);
 628
 629       return (std::__copy_move_backward_a2<__is_move_iterator<_BI1>::__value>
 630               (std::__miter_base(__first), std::__miter_base(__last),
 631                __result));
 632     }
 633
 634 #if __cplusplus >= 201103L
 635   /**
 636    *  @brief Moves the range [first,last) into result.
 637    *  @ingroup mutating_algorithms
 638    *  @param  __first  A bidirectional iterator.
 639    *  @param  __last   A bidirectional iterator.
 640    *  @param  __result A bidirectional iterator.
 641    *  @return   result - (first - last)
 642    *
 643    *  The function has the same effect as move, but starts at the end of the
 644    *  range and works its way to the start, returning the start of the result.
 645    *  This inline function will boil down to a call to @c memmove whenever
 646    *  possible.  Failing that, if random access iterators are passed, then the
 647    *  loop count will be known (and therefore a candidate for compiler
 648    *  optimizations such as unrolling).
 649    *
 650    *  Result may not be in the range (first,last].  Use move instead.  Note
 651    *  that the start of the output range may overlap [first,last).
 652   */
 653   template<typename _BI1, typename _BI2>
 654     inline _BI2
 655     move_backward(_BI1 __first, _BI1 __last, _BI2 __result)
 656     {
 657       // concept requirements
 658       __glibcxx_function_requires(_BidirectionalIteratorConcept<_BI1>)
 659       __glibcxx_function_requires(_Mutable_BidirectionalIteratorConcept<_BI2>)
 660       __glibcxx_function_requires(_ConvertibleConcept<
 661             typename iterator_traits<_BI1>::value_type,
 662             typename iterator_traits<_BI2>::value_type>)
 663       __glibcxx_requires_valid_range(__first, __last);
 664
 665       return std::__copy_move_backward_a2<true>(std::__miter_base(__first),
 666                                                 std::__miter_base(__last),
 667                                                 __result);
 668     }
 669
 670 #define _GLIBCXX_MOVE_BACKWARD3(_Tp, _Up, _Vp) std::move_backward(_Tp, _Up, _Vp)
 671 #else
 672 #define _GLIBCXX_MOVE_BACKWARD3(_Tp, _Up, _Vp) std::copy_backward(_Tp, _Up, _Vp)
 673 #endif
 674
 675   template<typename _ForwardIterator, typename _Tp>
 676     inline typename
 677     __gnu_cxx::__enable_if<!__is_scalar<_Tp>::__value, void>::__type
 678     __fill_a(_ForwardIterator __first, _ForwardIterator __last,
 679              const _Tp& __value)
 680     {
 681       for (; __first != __last; ++__first)
 682         *__first = __value;
 683     }
 684
 685   template<typename _ForwardIterator, typename _Tp>
 686     inline typename
 687     __gnu_cxx::__enable_if<__is_scalar<_Tp>::__value, void>::__type
 688     __fill_a(_ForwardIterator __first, _ForwardIterator __last,
 689              const _Tp& __value)
 690     {
 691       const _Tp __tmp = __value;
 692       for (; __first != __last; ++__first)
 693         *__first = __tmp;
 694     }
 695
 696   // Specialization: for char types we can use memset.
 697   template<typename _Tp>
 698     inline typename
 699     __gnu_cxx::__enable_if<__is_byte<_Tp>::__value, void>::__type
 700     __fill_a(_Tp* __first, _Tp* __last, const _Tp& __c)
 701     {
 702       const _Tp __tmp = __c;
 703       __builtin_memset(__first, static_cast<unsigned char>(__tmp),
 704                        __last - __first);
 705     }
 706
 707   /**
 708    *  @brief Fills the range [first,last) with copies of value.
 709    *  @ingroup mutating_algorithms
 710    *  @param  __first  A forward iterator.
 711    *  @param  __last   A forward iterator.
 712    *  @param  __value  A reference-to-const of arbitrary type.
 713    *  @return   Nothing.
 714    *
 715    *  This function fills a range with copies of the same value.  For char
 716    *  types filling contiguous areas of memory, this becomes an inline call
 717    *  to @c memset or @c wmemset.
 718   */
 719   template<typename _ForwardIterator, typename _Tp>
 720     inline void
 721     fill(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value)
 722     {
 723       // concept requirements
 724       __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
 725                                   _ForwardIterator>)
 726       __glibcxx_requires_valid_range(__first, __last);
 727
 728       std::__fill_a(std::__niter_base(__first), std::__niter_base(__last),
 729                     __value);
 730     }
 731
 732   template<typename _OutputIterator, typename _Size, typename _Tp>
 733     inline typename
 734     __gnu_cxx::__enable_if<!__is_scalar<_Tp>::__value, _OutputIterator>::__type
 735     __fill_n_a(_OutputIterator __first, _Size __n, const _Tp& __value)
 736     {
 737       for (__decltype(__n + 0) __niter = __n;
 738            __niter > 0; --__niter, ++__first)
 739         *__first = __value;
 740       return __first;
 741     }
 742
 743   template<typename _OutputIterator, typename _Size, typename _Tp>
 744     inline typename
 745     __gnu_cxx::__enable_if<__is_scalar<_Tp>::__value, _OutputIterator>::__type
 746     __fill_n_a(_OutputIterator __first, _Size __n, const _Tp& __value)
 747     {
 748       const _Tp __tmp = __value;
 749       for (__decltype(__n + 0) __niter = __n;
 750            __niter > 0; --__niter, ++__first)
 751         *__first = __tmp;
 752       return __first;
 753     }
 754
 755   template<typename _Size, typename _Tp>
 756     inline typename
 757     __gnu_cxx::__enable_if<__is_byte<_Tp>::__value, _Tp*>::__type
 758     __fill_n_a(_Tp* __first, _Size __n, const _Tp& __c)
 759     {
 760       std::__fill_a(__first, __first + __n, __c);
 761       return __first + __n;
 762     }
 763
 764   /**
 765    *  @brief Fills the range [first,first+n) with copies of value.
 766    *  @ingroup mutating_algorithms
 767    *  @param  __first  An output iterator.
 768    *  @param  __n      The count of copies to perform.
 769    *  @param  __value  A reference-to-const of arbitrary type.
 770    *  @return   The iterator at first+n.
 771    *
 772    *  This function fills a range with copies of the same value.  For char
 773    *  types filling contiguous areas of memory, this becomes an inline call
 774    *  to @c memset or @ wmemset.
 775    *
 776    *  _GLIBCXX_RESOLVE_LIB_DEFECTS
 777    *  DR 865. More algorithms that throw away information
 778   */
 779   template<typename _OI, typename _Size, typename _Tp>
 780     inline _OI
 781     fill_n(_OI __first, _Size __n, const _Tp& __value)
 782     {
 783       // concept requirements
 784       __glibcxx_function_requires(_OutputIteratorConcept<_OI, _Tp>)
 785
 786       return _OI(std::__fill_n_a(std::__niter_base(__first), __n, __value));
 787     }
 788
 789   template<bool _BoolType>
 790     struct __equal
 791     {
 792       template<typename _II1, typename _II2>
 793         static bool
 794         equal(_II1 __first1, _II1 __last1, _II2 __first2)
 795         {
 796           for (; __first1 != __last1; ++__first1, ++__first2)
 797             if (!(*__first1 == *__first2))
 798               return false;
 799           return true;
 800         }
 801     };
 802
 803   template<>
 804     struct __equal<true>
 805     {
 806       template<typename _Tp>
 807         static bool
 808         equal(const _Tp* __first1, const _Tp* __last1, const _Tp* __first2)
 809         {
 810           return !__builtin_memcmp(__first1, __first2, sizeof(_Tp)
 811                                    * (__last1 - __first1));
 812         }
 813     };
 814
 815   template<typename _II1, typename _II2>
 816     inline bool
 817     __equal_aux(_II1 __first1, _II1 __last1, _II2 __first2)
 818     {
 819       typedef typename iterator_traits<_II1>::value_type _ValueType1;
 820       typedef typename iterator_traits<_II2>::value_type _ValueType2;
 821       const bool __simple = ((__is_integer<_ValueType1>::__value
 822                               || __is_pointer<_ValueType1>::__value)
 823                              && __is_pointer<_II1>::__value
 824                              && __is_pointer<_II2>::__value
 825                              && __are_same<_ValueType1, _ValueType2>::__value);
 826
 827       return std::__equal<__simple>::equal(__first1, __last1, __first2);
 828     }
 829
 830   template<typename, typename>
 831     struct __lc_rai
 832     {
 833       template<typename _II1, typename _II2>
 834         static _II1
 835         __newlast1(_II1, _II1 __last1, _II2, _II2)
 836         { return __last1; }
 837
 838       template<typename _II>
 839         static bool
 840         __cnd2(_II __first, _II __last)
 841         { return __first != __last; }
 842     };
 843
 844   template<>
 845     struct __lc_rai<random_access_iterator_tag, random_access_iterator_tag>
 846     {
 847       template<typename _RAI1, typename _RAI2>
 848         static _RAI1
 849         __newlast1(_RAI1 __first1, _RAI1 __last1,
 850                    _RAI2 __first2, _RAI2 __last2)
 851         {
 852           const typename iterator_traits<_RAI1>::difference_type
 853             __diff1 = __last1 - __first1;
 854           const typename iterator_traits<_RAI2>::difference_type
 855             __diff2 = __last2 - __first2;
 856           return __diff2 < __diff1 ? __first1 + __diff2 : __last1;
 857         }
 858
 859       template<typename _RAI>
 860         static bool
 861         __cnd2(_RAI, _RAI)
 862         { return true; }
 863     };
 864
 865   template<bool _BoolType>
 866     struct __lexicographical_compare
 867     {
 868       template<typename _II1, typename _II2>
 869         static bool __lc(_II1, _II1, _II2, _II2);
 870     };
 871
 872   template<bool _BoolType>
 873     template<typename _II1, typename _II2>
 874       bool
 875       __lexicographical_compare<_BoolType>::
 876       __lc(_II1 __first1, _II1 __last1, _II2 __first2, _II2 __last2)
 877       {
 878         typedef typename iterator_traits<_II1>::iterator_category _Category1;
 879         typedef typename iterator_traits<_II2>::iterator_category _Category2;
 880         typedef std::__lc_rai<_Category1, _Category2>   __rai_type;
 881
 882         __last1 = __rai_type::__newlast1(__first1, __last1,
 883                                          __first2, __last2);
 884         for (; __first1 != __last1 && __rai_type::__cnd2(__first2, __last2);
 885              ++__first1, ++__first2)
 886           {
 887             if (*__first1 < *__first2)
 888               return true;
 889             if (*__first2 < *__first1)
 890               return false;
 891           }
 892         return __first1 == __last1 && __first2 != __last2;
 893       }
 894
 895   template<>
 896     struct __lexicographical_compare<true>
 897     {
 898       template<typename _Tp, typename _Up>
 899         static bool
 900         __lc(const _Tp* __first1, const _Tp* __last1,
 901              const _Up* __first2, const _Up* __last2)
 902         {
 903           const size_t __len1 = __last1 - __first1;
 904           const size_t __len2 = __last2 - __first2;
 905           const int __result = __builtin_memcmp(__first1, __first2,
 906                                                 std::min(__len1, __len2));
 907           return __result != 0 ? __result < 0 : __len1 < __len2;
 908         }
 909     };
 910
 911   template<typename _II1, typename _II2>
 912     inline bool
 913     __lexicographical_compare_aux(_II1 __first1, _II1 __last1,
 914                                   _II2 __first2, _II2 __last2)
 915     {
 916       typedef typename iterator_traits<_II1>::value_type _ValueType1;
 917       typedef typename iterator_traits<_II2>::value_type _ValueType2;
 918       const bool __simple =
 919         (__is_byte<_ValueType1>::__value && __is_byte<_ValueType2>::__value
 920          && !__gnu_cxx::__numeric_traits<_ValueType1>::__is_signed
 921          && !__gnu_cxx::__numeric_traits<_ValueType2>::__is_signed
 922          && __is_pointer<_II1>::__value
 923          && __is_pointer<_II2>::__value);
 924
 925       return std::__lexicographical_compare<__simple>::__lc(__first1, __last1,
 926                                                             __first2, __last2);
 927     }
 928
 929   /**
 930    *  @brief Finds the first position in which @a val could be inserted
 931    *         without changing the ordering.
 932    *  @param  __first   An iterator.
 933    *  @param  __last    Another iterator.
 934    *  @param  __val     The search term.
 935    *  @return         An iterator pointing to the first element <em>not less
 936    *                  than</em> @a val, or end() if every element is less than
 937    *                  @a val.
 938    *  @ingroup binary_search_algorithms
 939   */
 940   template<typename _ForwardIterator, typename _Tp>
 941     _ForwardIterator
 942     lower_bound(_ForwardIterator __first, _ForwardIterator __last,
 943                 const _Tp& __val)
 944     {
 945 #ifdef _GLIBCXX_CONCEPT_CHECKS
 946       typedef typename iterator_traits<_ForwardIterator>::value_type
 947         _ValueType;
 948 #endif
 949       typedef typename iterator_traits<_ForwardIterator>::difference_type
 950         _DistanceType;
 951
 952       // concept requirements
 953       __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
 954       __glibcxx_function_requires(_LessThanOpConcept<_ValueType, _Tp>)
 955       __glibcxx_requires_partitioned_lower(__first, __last, __val);
 956
 957       _DistanceType __len = std::distance(__first, __last);
 958
 959       while (__len > 0)
 960         {
 961           _DistanceType __half = __len >> 1;
 962           _ForwardIterator __middle = __first;
 963           std::advance(__middle, __half);
 964           if (*__middle < __val)
 965             {
 966               __first = __middle;
 967               ++__first;
 968               __len = __len - __half - 1;
 969             }
 970           else
 971             __len = __half;
 972         }
 973       return __first;
 974     }
 975
 976   /// This is a helper function for the sort routines and for random.tcc.
 977   //  Precondition: __n > 0.
 978   inline _GLIBCXX_CONSTEXPR int
 979   __lg(int __n)
 980   { return sizeof(int) * __CHAR_BIT__  - 1 - __builtin_clz(__n); }
 981
 982   inline _GLIBCXX_CONSTEXPR unsigned
 983   __lg(unsigned __n)
 984   { return sizeof(int) * __CHAR_BIT__  - 1 - __builtin_clz(__n); }
 985
 986   inline _GLIBCXX_CONSTEXPR long
 987   __lg(long __n)
 988   { return sizeof(long) * __CHAR_BIT__ - 1 - __builtin_clzl(__n); }
 989
 990   inline _GLIBCXX_CONSTEXPR unsigned long
 991   __lg(unsigned long __n)
 992   { return sizeof(long) * __CHAR_BIT__ - 1 - __builtin_clzl(__n); }
 993
 994   inline _GLIBCXX_CONSTEXPR long long
 995   __lg(long long __n)
 996   { return sizeof(long long) * __CHAR_BIT__ - 1 - __builtin_clzll(__n); }
 997
 998   inline _GLIBCXX_CONSTEXPR unsigned long long
 999   __lg(unsigned long long __n)
1000   { return sizeof(long long) * __CHAR_BIT__ - 1 - __builtin_clzll(__n); }
1001
1002 _GLIBCXX_END_NAMESPACE_VERSION
1003
1004 _GLIBCXX_BEGIN_NAMESPACE_ALGO
1005
1006   /**
1007    *  @brief Tests a range for element-wise equality.
1008    *  @ingroup non_mutating_algorithms
1009    *  @param  __first1  An input iterator.
1010    *  @param  __last1   An input iterator.
1011    *  @param  __first2  An input iterator.
1012    *  @return   A boolean true or false.
1013    *
1014    *  This compares the elements of two ranges using @c == and returns true or
1015    *  false depending on whether all of the corresponding elements of the
1016    *  ranges are equal.
1017   */
1018   template<typename _II1, typename _II2>
1019     inline bool
1020     equal(_II1 __first1, _II1 __last1, _II2 __first2)
1021     {
1022       // concept requirements
1023       __glibcxx_function_requires(_InputIteratorConcept<_II1>)
1024       __glibcxx_function_requires(_InputIteratorConcept<_II2>)
1025       __glibcxx_function_requires(_EqualOpConcept<
1026             typename iterator_traits<_II1>::value_type,
1027             typename iterator_traits<_II2>::value_type>)
1028       __glibcxx_requires_valid_range(__first1, __last1);
1029
1030       return std::__equal_aux(std::__niter_base(__first1),
1031                               std::__niter_base(__last1),
1032                               std::__niter_base(__first2));
1033     }
1034
1035   /**
1036    *  @brief Tests a range for element-wise equality.
1037    *  @ingroup non_mutating_algorithms
1038    *  @param  __first1  An input iterator.
1039    *  @param  __last1   An input iterator.
1040    *  @param  __first2  An input iterator.
1041    *  @param __binary_pred A binary predicate @link functors
1042    *                  functor@endlink.
1043    *  @return         A boolean true or false.
1044    *
1045    *  This compares the elements of two ranges using the binary_pred
1046    *  parameter, and returns true or
1047    *  false depending on whether all of the corresponding elements of the
1048    *  ranges are equal.
1049   */
1050   template<typename _IIter1, typename _IIter2, typename _BinaryPredicate>
1051     inline bool
1052     equal(_IIter1 __first1, _IIter1 __last1,
1053           _IIter2 __first2, _BinaryPredicate __binary_pred)
1054     {
1055       // concept requirements
1056       __glibcxx_function_requires(_InputIteratorConcept<_IIter1>)
1057       __glibcxx_function_requires(_InputIteratorConcept<_IIter2>)
1058       __glibcxx_requires_valid_range(__first1, __last1);
1059
1060       for (; __first1 != __last1; ++__first1, ++__first2)
1061         if (!bool(__binary_pred(*__first1, *__first2)))
1062           return false;
1063       return true;
1064     }
1065
1066 #if __cplusplus > 201103L
1067   /**
1068    *  @brief Tests a range for element-wise equality.
1069    *  @ingroup non_mutating_algorithms
1070    *  @param  __first1  An input iterator.
1071    *  @param  __last1   An input iterator.
1072    *  @param  __first2  An input iterator.
1073    *  @param  __last2   An input iterator.
1074    *  @return   A boolean true or false.
1075    *
1076    *  This compares the elements of two ranges using @c == and returns true or
1077    *  false depending on whether all of the corresponding elements of the
1078    *  ranges are equal.
1079   */
1080   template<typename _II1, typename _II2>
1081     inline bool
1082     equal(_II1 __first1, _II1 __last1, _II2 __first2, _II2 __last2)
1083     {
1084       // concept requirements
1085       __glibcxx_function_requires(_InputIteratorConcept<_II1>)
1086       __glibcxx_function_requires(_InputIteratorConcept<_II2>)
1087       __glibcxx_function_requires(_EqualOpConcept<
1088             typename iterator_traits<_II1>::value_type,
1089             typename iterator_traits<_II2>::value_type>)
1090       __glibcxx_requires_valid_range(__first1, __last1);
1091       __glibcxx_requires_valid_range(__first2, __last2);
1092
1093       using _RATag = random_access_iterator_tag;
1094       using _Cat1 = typename iterator_traits<_II1>::iterator_category;
1095       using _Cat2 = typename iterator_traits<_II2>::iterator_category;
1096       using _RAIters = __and_<is_same<_Cat1, _RATag>, is_same<_Cat2, _RATag>>;
1097       if (_RAIters())
1098         {
1099           auto __d1 = std::distance(__first1, __last1);
1100           auto __d2 = std::distance(__first2, __last2);
1101           if (__d1 != __d2)
1102             return false;
1103           return std::equal(__first1, __last1, __first2);
1104         }
1105
1106       for (; __first1 != __last1 && __first2 != __last2; ++__first1, ++__first2)
1107         if (!(*__first1 == *__first2))
1108           return false;
1109       return __first1 == __last1 && __first2 == __last2;
1110     }
1111
1112   /**
1113    *  @brief Tests a range for element-wise equality.
1114    *  @ingroup non_mutating_algorithms
1115    *  @param  __first1  An input iterator.
1116    *  @param  __last1   An input iterator.
1117    *  @param  __first2  An input iterator.
1118    *  @param  __last2   An input iterator.
1119    *  @param __binary_pred A binary predicate @link functors
1120    *                  functor@endlink.
1121    *  @return         A boolean true or false.
1122    *
1123    *  This compares the elements of two ranges using the binary_pred
1124    *  parameter, and returns true or
1125    *  false depending on whether all of the corresponding elements of the
1126    *  ranges are equal.
1127   */
1128   template<typename _IIter1, typename _IIter2, typename _BinaryPredicate>
1129     inline bool
1130     equal(_IIter1 __first1, _IIter1 __last1,
1131           _IIter2 __first2, _IIter2 __last2, _BinaryPredicate __binary_pred)
1132     {
1133       // concept requirements
1134       __glibcxx_function_requires(_InputIteratorConcept<_IIter1>)
1135       __glibcxx_function_requires(_InputIteratorConcept<_IIter2>)
1136       __glibcxx_requires_valid_range(__first1, __last1);
1137       __glibcxx_requires_valid_range(__first2, __last2);
1138
1139       using _RATag = random_access_iterator_tag;
1140       using _Cat1 = typename iterator_traits<_IIter1>::iterator_category;
1141       using _Cat2 = typename iterator_traits<_IIter2>::iterator_category;
1142       using _RAIters = __and_<is_same<_Cat1, _RATag>, is_same<_Cat2, _RATag>>;
1143       if (_RAIters())
1144         {
1145           auto __d1 = std::distance(__first1, __last1);
1146           auto __d2 = std::distance(__first2, __last2);
1147           if (__d1 != __d2)
1148             return false;
1149           return std::equal(__first1, __last1, __first2, __binary_pred);
1150         }
1151
1152       for (; __first1 != __last1 && __first2 != __last2; ++__first1, ++__first2)
1153         if (!bool(__binary_pred(*__first1, *__first2)))
1154           return false;
1155       return __first1 == __last1 && __first2 == __last2;
1156     }
1157 #endif
1158
1159   /**
1160    *  @brief Performs @b dictionary comparison on ranges.
1161    *  @ingroup sorting_algorithms
1162    *  @param  __first1  An input iterator.
1163    *  @param  __last1   An input iterator.
1164    *  @param  __first2  An input iterator.
1165    *  @param  __last2   An input iterator.
1166    *  @return   A boolean true or false.
1167    *
1168    *  <em>Returns true if the sequence of elements defined by the range
1169    *  [first1,last1) is lexicographically less than the sequence of elements
1170    *  defined by the range [first2,last2).  Returns false otherwise.</em>
1171    *  (Quoted from [25.3.8]/1.)  If the iterators are all character pointers,
1172    *  then this is an inline call to @c memcmp.
1173   */
1174   template<typename _II1, typename _II2>
1175     inline bool
1176     lexicographical_compare(_II1 __first1, _II1 __last1,
1177                             _II2 __first2, _II2 __last2)
1178     {
1179 #ifdef _GLIBCXX_CONCEPT_CHECKS
1180       // concept requirements
1181       typedef typename iterator_traits<_II1>::value_type _ValueType1;
1182       typedef typename iterator_traits<_II2>::value_type _ValueType2;
1183 #endif
1184       __glibcxx_function_requires(_InputIteratorConcept<_II1>)
1185       __glibcxx_function_requires(_InputIteratorConcept<_II2>)
1186       __glibcxx_function_requires(_LessThanOpConcept<_ValueType1, _ValueType2>)
1187       __glibcxx_function_requires(_LessThanOpConcept<_ValueType2, _ValueType1>)
1188       __glibcxx_requires_valid_range(__first1, __last1);
1189       __glibcxx_requires_valid_range(__first2, __last2);
1190
1191       return std::__lexicographical_compare_aux(std::__niter_base(__first1),
1192                                                 std::__niter_base(__last1),
1193                                                 std::__niter_base(__first2),
1194                                                 std::__niter_base(__last2));
1195     }
1196
1197   /**
1198    *  @brief Performs @b dictionary comparison on ranges.
1199    *  @ingroup sorting_algorithms
1200    *  @param  __first1  An input iterator.
1201    *  @param  __last1   An input iterator.
1202    *  @param  __first2  An input iterator.
1203    *  @param  __last2   An input iterator.
1204    *  @param  __comp  A @link comparison_functors comparison functor@endlink.
1205    *  @return   A boolean true or false.
1206    *
1207    *  The same as the four-parameter @c lexicographical_compare, but uses the
1208    *  comp parameter instead of @c <.
1209   */
1210   template<typename _II1, typename _II2, typename _Compare>
1211     bool
1212     lexicographical_compare(_II1 __first1, _II1 __last1,
1213                             _II2 __first2, _II2 __last2, _Compare __comp)
1214     {
1215       typedef typename iterator_traits<_II1>::iterator_category _Category1;
1216       typedef typename iterator_traits<_II2>::iterator_category _Category2;
1217       typedef std::__lc_rai<_Category1, _Category2>     __rai_type;
1218
1219       // concept requirements
1220       __glibcxx_function_requires(_InputIteratorConcept<_II1>)
1221       __glibcxx_function_requires(_InputIteratorConcept<_II2>)
1222       __glibcxx_requires_valid_range(__first1, __last1);
1223       __glibcxx_requires_valid_range(__first2, __last2);
1224
1225       __last1 = __rai_type::__newlast1(__first1, __last1, __first2, __last2);
1226       for (; __first1 != __last1 && __rai_type::__cnd2(__first2, __last2);
1227            ++__first1, ++__first2)
1228         {
1229           if (__comp(*__first1, *__first2))
1230             return true;
1231           if (__comp(*__first2, *__first1))
1232             return false;
1233         }
1234       return __first1 == __last1 && __first2 != __last2;
1235     }
1236
1237   /**
1238    *  @brief Finds the places in ranges which don't match.
1239    *  @ingroup non_mutating_algorithms
1240    *  @param  __first1  An input iterator.
1241    *  @param  __last1   An input iterator.
1242    *  @param  __first2  An input iterator.
1243    *  @return   A pair of iterators pointing to the first mismatch.
1244    *
1245    *  This compares the elements of two ranges using @c == and returns a pair
1246    *  of iterators.  The first iterator points into the first range, the
1247    *  second iterator points into the second range, and the elements pointed
1248    *  to by the iterators are not equal.
1249   */
1250   template<typename _InputIterator1, typename _InputIterator2>
1251     pair<_InputIterator1, _InputIterator2>
1252     mismatch(_InputIterator1 __first1, _InputIterator1 __last1,
1253              _InputIterator2 __first2)
1254     {
1255       // concept requirements
1256       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
1257       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
1258       __glibcxx_function_requires(_EqualOpConcept<
1259             typename iterator_traits<_InputIterator1>::value_type,
1260             typename iterator_traits<_InputIterator2>::value_type>)
1261       __glibcxx_requires_valid_range(__first1, __last1);
1262
1263       while (__first1 != __last1 && *__first1 == *__first2)
1264         {
1265           ++__first1;
1266           ++__first2;
1267         }
1268       return pair<_InputIterator1, _InputIterator2>(__first1, __first2);
1269     }
1270
1271   /**
1272    *  @brief Finds the places in ranges which don't match.
1273    *  @ingroup non_mutating_algorithms
1274    *  @param  __first1  An input iterator.
1275    *  @param  __last1   An input iterator.
1276    *  @param  __first2  An input iterator.
1277    *  @param __binary_pred A binary predicate @link functors
1278    *         functor@endlink.
1279    *  @return   A pair of iterators pointing to the first mismatch.
1280    *
1281    *  This compares the elements of two ranges using the binary_pred
1282    *  parameter, and returns a pair
1283    *  of iterators.  The first iterator points into the first range, the
1284    *  second iterator points into the second range, and the elements pointed
1285    *  to by the iterators are not equal.
1286   */
1287   template<typename _InputIterator1, typename _InputIterator2,
1288            typename _BinaryPredicate>
1289     pair<_InputIterator1, _InputIterator2>
1290     mismatch(_InputIterator1 __first1, _InputIterator1 __last1,
1291              _InputIterator2 __first2, _BinaryPredicate __binary_pred)
1292     {
1293       // concept requirements
1294       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
1295       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
1296       __glibcxx_requires_valid_range(__first1, __last1);
1297
1298       while (__first1 != __last1 && bool(__binary_pred(*__first1, *__first2)))
1299         {
1300           ++__first1;
1301           ++__first2;
1302         }
1303       return pair<_InputIterator1, _InputIterator2>(__first1, __first2);
1304     }
1305
1306 #if __cplusplus > 201103L
1307   /**
1308    *  @brief Finds the places in ranges which don't match.
1309    *  @ingroup non_mutating_algorithms
1310    *  @param  __first1  An input iterator.
1311    *  @param  __last1   An input iterator.
1312    *  @param  __first2  An input iterator.
1313    *  @param  __last2   An input iterator.
1314    *  @return   A pair of iterators pointing to the first mismatch.
1315    *
1316    *  This compares the elements of two ranges using @c == and returns a pair
1317    *  of iterators.  The first iterator points into the first range, the
1318    *  second iterator points into the second range, and the elements pointed
1319    *  to by the iterators are not equal.
1320   */
1321   template<typename _InputIterator1, typename _InputIterator2>
1322     pair<_InputIterator1, _InputIterator2>
1323     mismatch(_InputIterator1 __first1, _InputIterator1 __last1,
1324              _InputIterator2 __first2, _InputIterator2 __last2)
1325     {
1326       // concept requirements
1327       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
1328       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
1329       __glibcxx_function_requires(_EqualOpConcept<
1330             typename iterator_traits<_InputIterator1>::value_type,
1331             typename iterator_traits<_InputIterator2>::value_type>)
1332       __glibcxx_requires_valid_range(__first1, __last1);
1333       __glibcxx_requires_valid_range(__first2, __last2);
1334
1335       while (__first1 != __last1 && __first2 != __last2
1336           && *__first1 == *__first2)
1337         {
1338           ++__first1;
1339           ++__first2;
1340         }
1341       return pair<_InputIterator1, _InputIterator2>(__first1, __first2);
1342     }
1343
1344   /**
1345    *  @brief Finds the places in ranges which don't match.
1346    *  @ingroup non_mutating_algorithms
1347    *  @param  __first1  An input iterator.
1348    *  @param  __last1   An input iterator.
1349    *  @param  __first2  An input iterator.
1350    *  @param  __last2   An input iterator.
1351    *  @param __binary_pred A binary predicate @link functors
1352    *         functor@endlink.
1353    *  @return   A pair of iterators pointing to the first mismatch.
1354    *
1355    *  This compares the elements of two ranges using the binary_pred
1356    *  parameter, and returns a pair
1357    *  of iterators.  The first iterator points into the first range, the
1358    *  second iterator points into the second range, and the elements pointed
1359    *  to by the iterators are not equal.
1360   */
1361   template<typename _InputIterator1, typename _InputIterator2,
1362            typename _BinaryPredicate>
1363     pair<_InputIterator1, _InputIterator2>
1364     mismatch(_InputIterator1 __first1, _InputIterator1 __last1,
1365              _InputIterator2 __first2, _InputIterator2 __last2,
1366              _BinaryPredicate __binary_pred)
1367     {
1368       // concept requirements
1369       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
1370       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
1371       __glibcxx_requires_valid_range(__first1, __last1);
1372       __glibcxx_requires_valid_range(__first2, __last2);
1373
1374       while (__first1 != __last1 && __first2 != __last2
1375           && bool(__binary_pred(*__first1, *__first2)))
1376         {
1377           ++__first1;
1378           ++__first2;
1379         }
1380       return pair<_InputIterator1, _InputIterator2>(__first1, __first2);
1381     }
1382 #endif
1383
1384 _GLIBCXX_END_NAMESPACE_ALGO
1385 } // namespace std
1386
1387 // NB: This file is included within many other C++ includes, as a way
1388 // of getting the base algorithms. So, make sure that parallel bits
1389 // come in too if requested.
1390 #ifdef _GLIBCXX_PARALLEL
1391 # include <parallel/algobase.h>
1392 #endif
1393
1394 #endif