stl_algobase.h

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00001 // Core algorithmic facilities -*- C++ -*-
00002 
00003 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
00004 // Free Software Foundation, Inc.
00005 //
00006 // This file is part of the GNU ISO C++ Library.  This library is free
00007 // software; you can redistribute it and/or modify it under the
00008 // terms of the GNU General Public License as published by the
00009 // Free Software Foundation; either version 3, or (at your option)
00010 // any later version.
00011 
00012 // This library is distributed in the hope that it will be useful,
00013 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00014 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015 // GNU General Public License for more details.
00016 
00017 // Under Section 7 of GPL version 3, you are granted additional
00018 // permissions described in the GCC Runtime Library Exception, version
00019 // 3.1, as published by the Free Software Foundation.
00020 
00021 // You should have received a copy of the GNU General Public License and
00022 // a copy of the GCC Runtime Library Exception along with this program;
00023 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00024 // <http://www.gnu.org/licenses/>.
00025 
00026 /*
00027  *
00028  * Copyright (c) 1994
00029  * Hewlett-Packard Company
00030  *
00031  * Permission to use, copy, modify, distribute and sell this software
00032  * and its documentation for any purpose is hereby granted without fee,
00033  * provided that the above copyright notice appear in all copies and
00034  * that both that copyright notice and this permission notice appear
00035  * in supporting documentation.  Hewlett-Packard Company makes no
00036  * representations about the suitability of this software for any
00037  * purpose.  It is provided "as is" without express or implied warranty.
00038  *
00039  *
00040  * Copyright (c) 1996-1998
00041  * Silicon Graphics Computer Systems, Inc.
00042  *
00043  * Permission to use, copy, modify, distribute and sell this software
00044  * and its documentation for any purpose is hereby granted without fee,
00045  * provided that the above copyright notice appear in all copies and
00046  * that both that copyright notice and this permission notice appear
00047  * in supporting documentation.  Silicon Graphics makes no
00048  * representations about the suitability of this software for any
00049  * purpose.  It is provided "as is" without express or implied warranty.
00050  */
00051 
00052 /** @file stl_algobase.h
00053  *  This is an internal header file, included by other library headers.
00054  *  You should not attempt to use it directly.
00055  */
00056 
00057 #ifndef _STL_ALGOBASE_H
00058 #define _STL_ALGOBASE_H 1
00059 
00060 #include <bits/c++config.h>
00061 #include <cstddef>
00062 #include <bits/functexcept.h>
00063 #include <bits/cpp_type_traits.h>
00064 #include <ext/type_traits.h>
00065 #include <ext/numeric_traits.h>
00066 #include <bits/stl_pair.h>
00067 #include <bits/stl_iterator_base_types.h>
00068 #include <bits/stl_iterator_base_funcs.h>
00069 #include <bits/stl_iterator.h>
00070 #include <bits/concept_check.h>
00071 #include <debug/debug.h>
00072 #include <bits/move.h> // For std::swap and _GLIBCXX_MOVE
00073 
00074 _GLIBCXX_BEGIN_NAMESPACE(std)
00075 
00076   // See http://gcc.gnu.org/ml/libstdc++/2004-08/msg00167.html: in a
00077   // nutshell, we are partially implementing the resolution of DR 187,
00078   // when it's safe, i.e., the value_types are equal.
00079   template<bool _BoolType>
00080     struct __iter_swap
00081     {
00082       template<typename _ForwardIterator1, typename _ForwardIterator2>
00083         static void
00084         iter_swap(_ForwardIterator1 __a, _ForwardIterator2 __b)
00085         {
00086           typedef typename iterator_traits<_ForwardIterator1>::value_type
00087             _ValueType1;
00088           _ValueType1 __tmp = _GLIBCXX_MOVE(*__a);
00089           *__a = _GLIBCXX_MOVE(*__b);
00090           *__b = _GLIBCXX_MOVE(__tmp);
00091     }
00092     };
00093 
00094   template<>
00095     struct __iter_swap<true>
00096     {
00097       template<typename _ForwardIterator1, typename _ForwardIterator2>
00098         static void 
00099         iter_swap(_ForwardIterator1 __a, _ForwardIterator2 __b)
00100         {
00101           swap(*__a, *__b);
00102         }
00103     };
00104 
00105   /**
00106    *  @brief Swaps the contents of two iterators.
00107    *  @ingroup mutating_algorithms
00108    *  @param  a  An iterator.
00109    *  @param  b  Another iterator.
00110    *  @return   Nothing.
00111    *
00112    *  This function swaps the values pointed to by two iterators, not the
00113    *  iterators themselves.
00114   */
00115   template<typename _ForwardIterator1, typename _ForwardIterator2>
00116     inline void
00117     iter_swap(_ForwardIterator1 __a, _ForwardIterator2 __b)
00118     {
00119       typedef typename iterator_traits<_ForwardIterator1>::value_type
00120     _ValueType1;
00121       typedef typename iterator_traits<_ForwardIterator2>::value_type
00122     _ValueType2;
00123 
00124       // concept requirements
00125       __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
00126                   _ForwardIterator1>)
00127       __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
00128                   _ForwardIterator2>)
00129       __glibcxx_function_requires(_ConvertibleConcept<_ValueType1,
00130                   _ValueType2>)
00131       __glibcxx_function_requires(_ConvertibleConcept<_ValueType2,
00132                   _ValueType1>)
00133 
00134       typedef typename iterator_traits<_ForwardIterator1>::reference
00135     _ReferenceType1;
00136       typedef typename iterator_traits<_ForwardIterator2>::reference
00137     _ReferenceType2;
00138       std::__iter_swap<__are_same<_ValueType1, _ValueType2>::__value
00139     && __are_same<_ValueType1&, _ReferenceType1>::__value
00140     && __are_same<_ValueType2&, _ReferenceType2>::__value>::
00141     iter_swap(__a, __b);
00142     }
00143 
00144   /**
00145    *  @brief Swap the elements of two sequences.
00146    *  @ingroup mutating_algorithms
00147    *  @param  first1  A forward iterator.
00148    *  @param  last1   A forward iterator.
00149    *  @param  first2  A forward iterator.
00150    *  @return   An iterator equal to @p first2+(last1-first1).
00151    *
00152    *  Swaps each element in the range @p [first1,last1) with the
00153    *  corresponding element in the range @p [first2,(last1-first1)).
00154    *  The ranges must not overlap.
00155   */
00156   template<typename _ForwardIterator1, typename _ForwardIterator2>
00157     _ForwardIterator2
00158     swap_ranges(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
00159         _ForwardIterator2 __first2)
00160     {
00161       // concept requirements
00162       __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
00163                   _ForwardIterator1>)
00164       __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
00165                   _ForwardIterator2>)
00166       __glibcxx_requires_valid_range(__first1, __last1);
00167 
00168       for (; __first1 != __last1; ++__first1, ++__first2)
00169     std::iter_swap(__first1, __first2);
00170       return __first2;
00171     }
00172 
00173   /**
00174    *  @brief This does what you think it does.
00175    *  @ingroup sorting_algorithms
00176    *  @param  a  A thing of arbitrary type.
00177    *  @param  b  Another thing of arbitrary type.
00178    *  @return   The lesser of the parameters.
00179    *
00180    *  This is the simple classic generic implementation.  It will work on
00181    *  temporary expressions, since they are only evaluated once, unlike a
00182    *  preprocessor macro.
00183   */
00184   template<typename _Tp>
00185     inline const _Tp&
00186     min(const _Tp& __a, const _Tp& __b)
00187     {
00188       // concept requirements
00189       __glibcxx_function_requires(_LessThanComparableConcept<_Tp>)
00190       //return __b < __a ? __b : __a;
00191       if (__b < __a)
00192     return __b;
00193       return __a;
00194     }
00195 
00196   /**
00197    *  @brief This does what you think it does.
00198    *  @ingroup sorting_algorithms
00199    *  @param  a  A thing of arbitrary type.
00200    *  @param  b  Another thing of arbitrary type.
00201    *  @return   The greater of the parameters.
00202    *
00203    *  This is the simple classic generic implementation.  It will work on
00204    *  temporary expressions, since they are only evaluated once, unlike a
00205    *  preprocessor macro.
00206   */
00207   template<typename _Tp>
00208     inline const _Tp&
00209     max(const _Tp& __a, const _Tp& __b)
00210     {
00211       // concept requirements
00212       __glibcxx_function_requires(_LessThanComparableConcept<_Tp>)
00213       //return  __a < __b ? __b : __a;
00214       if (__a < __b)
00215     return __b;
00216       return __a;
00217     }
00218 
00219   /**
00220    *  @brief This does what you think it does.
00221    *  @ingroup sorting_algorithms
00222    *  @param  a  A thing of arbitrary type.
00223    *  @param  b  Another thing of arbitrary type.
00224    *  @param  comp  A @link comparison_functors comparison functor@endlink.
00225    *  @return   The lesser of the parameters.
00226    *
00227    *  This will work on temporary expressions, since they are only evaluated
00228    *  once, unlike a preprocessor macro.
00229   */
00230   template<typename _Tp, typename _Compare>
00231     inline const _Tp&
00232     min(const _Tp& __a, const _Tp& __b, _Compare __comp)
00233     {
00234       //return __comp(__b, __a) ? __b : __a;
00235       if (__comp(__b, __a))
00236     return __b;
00237       return __a;
00238     }
00239 
00240   /**
00241    *  @brief This does what you think it does.
00242    *  @ingroup sorting_algorithms
00243    *  @param  a  A thing of arbitrary type.
00244    *  @param  b  Another thing of arbitrary type.
00245    *  @param  comp  A @link comparison_functors comparison functor@endlink.
00246    *  @return   The greater of the parameters.
00247    *
00248    *  This will work on temporary expressions, since they are only evaluated
00249    *  once, unlike a preprocessor macro.
00250   */
00251   template<typename _Tp, typename _Compare>
00252     inline const _Tp&
00253     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
00254     {
00255       //return __comp(__a, __b) ? __b : __a;
00256       if (__comp(__a, __b))
00257     return __b;
00258       return __a;
00259     }
00260 
00261 
00262   // If _Iterator has a base returns it otherwise _Iterator is returned
00263   // untouched
00264   template<typename _Iterator, bool _HasBase>
00265     struct _Iter_base
00266     {
00267       typedef _Iterator iterator_type;
00268       static iterator_type
00269       _S_base(_Iterator __it)
00270       { return __it; }
00271     };
00272 
00273   template<typename _Iterator>
00274     struct _Iter_base<_Iterator, true>
00275     {
00276       typedef typename _Iterator::iterator_type iterator_type;
00277       static iterator_type
00278       _S_base(_Iterator __it)
00279       { return __it.base(); }
00280     };
00281 
00282   // If _Iterator is a __normal_iterator return its base (a plain pointer,
00283   // normally) otherwise return it untouched.  See copy, fill, ... 
00284   template<typename _Iterator>
00285     struct _Niter_base
00286     : _Iter_base<_Iterator, __is_normal_iterator<_Iterator>::__value>
00287     { };
00288 
00289   template<typename _Iterator>
00290     inline typename _Niter_base<_Iterator>::iterator_type
00291     __niter_base(_Iterator __it)
00292     { return std::_Niter_base<_Iterator>::_S_base(__it); }
00293 
00294   // Likewise, for move_iterator.
00295   template<typename _Iterator>
00296     struct _Miter_base
00297     : _Iter_base<_Iterator, __is_move_iterator<_Iterator>::__value>
00298     { };
00299 
00300   template<typename _Iterator>
00301     inline typename _Miter_base<_Iterator>::iterator_type
00302     __miter_base(_Iterator __it)
00303     { return std::_Miter_base<_Iterator>::_S_base(__it); }
00304 
00305   // All of these auxiliary structs serve two purposes.  (1) Replace
00306   // calls to copy with memmove whenever possible.  (Memmove, not memcpy,
00307   // because the input and output ranges are permitted to overlap.)
00308   // (2) If we're using random access iterators, then write the loop as
00309   // a for loop with an explicit count.
00310 
00311   template<bool, bool, typename>
00312     struct __copy_move
00313     {
00314       template<typename _II, typename _OI>
00315         static _OI
00316         __copy_m(_II __first, _II __last, _OI __result)
00317         {
00318       for (; __first != __last; ++__result, ++__first)
00319         *__result = *__first;
00320       return __result;
00321     }
00322     };
00323 
00324 #ifdef __GXX_EXPERIMENTAL_CXX0X__
00325   template<typename _Category>
00326     struct __copy_move<true, false, _Category>
00327     {
00328       template<typename _II, typename _OI>
00329         static _OI
00330         __copy_m(_II __first, _II __last, _OI __result)
00331         {
00332       for (; __first != __last; ++__result, ++__first)
00333         *__result = std::move(*__first);
00334       return __result;
00335     }
00336     };
00337 #endif
00338 
00339   template<>
00340     struct __copy_move<false, false, random_access_iterator_tag>
00341     {
00342       template<typename _II, typename _OI>
00343         static _OI
00344         __copy_m(_II __first, _II __last, _OI __result)
00345         { 
00346       typedef typename iterator_traits<_II>::difference_type _Distance;
00347       for(_Distance __n = __last - __first; __n > 0; --__n)
00348         {
00349           *__result = *__first;
00350           ++__first;
00351           ++__result;
00352         }
00353       return __result;
00354     }
00355     };
00356 
00357 #ifdef __GXX_EXPERIMENTAL_CXX0X__
00358   template<>
00359     struct __copy_move<true, false, random_access_iterator_tag>
00360     {
00361       template<typename _II, typename _OI>
00362         static _OI
00363         __copy_m(_II __first, _II __last, _OI __result)
00364         { 
00365       typedef typename iterator_traits<_II>::difference_type _Distance;
00366       for(_Distance __n = __last - __first; __n > 0; --__n)
00367         {
00368           *__result = std::move(*__first);
00369           ++__first;
00370           ++__result;
00371         }
00372       return __result;
00373     }
00374     };
00375 #endif
00376 
00377   template<bool _IsMove>
00378     struct __copy_move<_IsMove, true, random_access_iterator_tag>
00379     {
00380       template<typename _Tp>
00381         static _Tp*
00382         __copy_m(const _Tp* __first, const _Tp* __last, _Tp* __result)
00383         {
00384       const ptrdiff_t _Num = __last - __first;
00385       if (_Num)
00386         __builtin_memmove(__result, __first, sizeof(_Tp) * _Num);
00387       return __result + _Num;
00388     }
00389     };
00390 
00391   template<bool _IsMove, typename _II, typename _OI>
00392     inline _OI
00393     __copy_move_a(_II __first, _II __last, _OI __result)
00394     {
00395       typedef typename iterator_traits<_II>::value_type _ValueTypeI;
00396       typedef typename iterator_traits<_OI>::value_type _ValueTypeO;
00397       typedef typename iterator_traits<_II>::iterator_category _Category;
00398       const bool __simple = (__is_pod(_ValueTypeI)
00399                          && __is_pointer<_II>::__value
00400                          && __is_pointer<_OI>::__value
00401                  && __are_same<_ValueTypeI, _ValueTypeO>::__value);
00402 
00403       return std::__copy_move<_IsMove, __simple,
00404                           _Category>::__copy_m(__first, __last, __result);
00405     }
00406 
00407   // Helpers for streambuf iterators (either istream or ostream).
00408   // NB: avoid including <iosfwd>, relatively large.
00409   template<typename _CharT>
00410     struct char_traits;
00411 
00412   template<typename _CharT, typename _Traits>
00413     class istreambuf_iterator;
00414 
00415   template<typename _CharT, typename _Traits>
00416     class ostreambuf_iterator;
00417 
00418   template<bool _IsMove, typename _CharT>
00419     typename __gnu_cxx::__enable_if<__is_char<_CharT>::__value, 
00420          ostreambuf_iterator<_CharT, char_traits<_CharT> > >::__type
00421     __copy_move_a2(_CharT*, _CharT*,
00422            ostreambuf_iterator<_CharT, char_traits<_CharT> >);
00423 
00424   template<bool _IsMove, typename _CharT>
00425     typename __gnu_cxx::__enable_if<__is_char<_CharT>::__value, 
00426          ostreambuf_iterator<_CharT, char_traits<_CharT> > >::__type
00427     __copy_move_a2(const _CharT*, const _CharT*,
00428            ostreambuf_iterator<_CharT, char_traits<_CharT> >);
00429 
00430   template<bool _IsMove, typename _CharT>
00431     typename __gnu_cxx::__enable_if<__is_char<_CharT>::__value,
00432                     _CharT*>::__type
00433     __copy_move_a2(istreambuf_iterator<_CharT, char_traits<_CharT> >,
00434            istreambuf_iterator<_CharT, char_traits<_CharT> >, _CharT*);
00435 
00436   template<bool _IsMove, typename _II, typename _OI>
00437     inline _OI
00438     __copy_move_a2(_II __first, _II __last, _OI __result)
00439     {
00440       return _OI(std::__copy_move_a<_IsMove>(std::__niter_base(__first),
00441                          std::__niter_base(__last),
00442                          std::__niter_base(__result)));
00443     }
00444 
00445   /**
00446    *  @brief Copies the range [first,last) into result.
00447    *  @ingroup mutating_algorithms
00448    *  @param  first  An input iterator.
00449    *  @param  last   An input iterator.
00450    *  @param  result An output iterator.
00451    *  @return   result + (first - last)
00452    *
00453    *  This inline function will boil down to a call to @c memmove whenever
00454    *  possible.  Failing that, if random access iterators are passed, then the
00455    *  loop count will be known (and therefore a candidate for compiler
00456    *  optimizations such as unrolling).  Result may not be contained within
00457    *  [first,last); the copy_backward function should be used instead.
00458    *
00459    *  Note that the end of the output range is permitted to be contained
00460    *  within [first,last).
00461   */
00462   template<typename _II, typename _OI>
00463     inline _OI
00464     copy(_II __first, _II __last, _OI __result)
00465     {
00466       // concept requirements
00467       __glibcxx_function_requires(_InputIteratorConcept<_II>)
00468       __glibcxx_function_requires(_OutputIteratorConcept<_OI,
00469         typename iterator_traits<_II>::value_type>)
00470       __glibcxx_requires_valid_range(__first, __last);
00471 
00472       return (std::__copy_move_a2<__is_move_iterator<_II>::__value>
00473           (std::__miter_base(__first), std::__miter_base(__last),
00474            __result));
00475     }
00476 
00477 #ifdef __GXX_EXPERIMENTAL_CXX0X__
00478   /**
00479    *  @brief Moves the range [first,last) into result.
00480    *  @ingroup mutating_algorithms
00481    *  @param  first  An input iterator.
00482    *  @param  last   An input iterator.
00483    *  @param  result An output iterator.
00484    *  @return   result + (first - last)
00485    *
00486    *  This inline function will boil down to a call to @c memmove whenever
00487    *  possible.  Failing that, if random access iterators are passed, then the
00488    *  loop count will be known (and therefore a candidate for compiler
00489    *  optimizations such as unrolling).  Result may not be contained within
00490    *  [first,last); the move_backward function should be used instead.
00491    *
00492    *  Note that the end of the output range is permitted to be contained
00493    *  within [first,last).
00494   */
00495   template<typename _II, typename _OI>
00496     inline _OI
00497     move(_II __first, _II __last, _OI __result)
00498     {
00499       // concept requirements
00500       __glibcxx_function_requires(_InputIteratorConcept<_II>)
00501       __glibcxx_function_requires(_OutputIteratorConcept<_OI,
00502         typename iterator_traits<_II>::value_type>)
00503       __glibcxx_requires_valid_range(__first, __last);
00504 
00505       return std::__copy_move_a2<true>(std::__miter_base(__first),
00506                        std::__miter_base(__last), __result);
00507     }
00508 
00509 #define _GLIBCXX_MOVE3(_Tp, _Up, _Vp) std::move(_Tp, _Up, _Vp)
00510 #else
00511 #define _GLIBCXX_MOVE3(_Tp, _Up, _Vp) std::copy(_Tp, _Up, _Vp)
00512 #endif
00513 
00514   template<bool, bool, typename>
00515     struct __copy_move_backward
00516     {
00517       template<typename _BI1, typename _BI2>
00518         static _BI2
00519         __copy_move_b(_BI1 __first, _BI1 __last, _BI2 __result)
00520         {
00521       while (__first != __last)
00522         *--__result = *--__last;
00523       return __result;
00524     }
00525     };
00526 
00527 #ifdef __GXX_EXPERIMENTAL_CXX0X__
00528   template<typename _Category>
00529     struct __copy_move_backward<true, false, _Category>
00530     {
00531       template<typename _BI1, typename _BI2>
00532         static _BI2
00533         __copy_move_b(_BI1 __first, _BI1 __last, _BI2 __result)
00534         {
00535       while (__first != __last)
00536         *--__result = std::move(*--__last);
00537       return __result;
00538     }
00539     };
00540 #endif
00541 
00542   template<>
00543     struct __copy_move_backward<false, false, random_access_iterator_tag>
00544     {
00545       template<typename _BI1, typename _BI2>
00546         static _BI2
00547         __copy_move_b(_BI1 __first, _BI1 __last, _BI2 __result)
00548         {
00549       typename iterator_traits<_BI1>::difference_type __n;
00550       for (__n = __last - __first; __n > 0; --__n)
00551         *--__result = *--__last;
00552       return __result;
00553     }
00554     };
00555 
00556 #ifdef __GXX_EXPERIMENTAL_CXX0X__
00557   template<>
00558     struct __copy_move_backward<true, false, random_access_iterator_tag>
00559     {
00560       template<typename _BI1, typename _BI2>
00561         static _BI2
00562         __copy_move_b(_BI1 __first, _BI1 __last, _BI2 __result)
00563         {
00564       typename iterator_traits<_BI1>::difference_type __n;
00565       for (__n = __last - __first; __n > 0; --__n)
00566         *--__result = std::move(*--__last);
00567       return __result;
00568     }
00569     };
00570 #endif
00571 
00572   template<bool _IsMove>
00573     struct __copy_move_backward<_IsMove, true, random_access_iterator_tag>
00574     {
00575       template<typename _Tp>
00576         static _Tp*
00577         __copy_move_b(const _Tp* __first, const _Tp* __last, _Tp* __result)
00578         {
00579       const ptrdiff_t _Num = __last - __first;
00580       if (_Num)
00581         __builtin_memmove(__result - _Num, __first, sizeof(_Tp) * _Num);
00582       return __result - _Num;
00583     }
00584     };
00585 
00586   template<bool _IsMove, typename _BI1, typename _BI2>
00587     inline _BI2
00588     __copy_move_backward_a(_BI1 __first, _BI1 __last, _BI2 __result)
00589     {
00590       typedef typename iterator_traits<_BI1>::value_type _ValueType1;
00591       typedef typename iterator_traits<_BI2>::value_type _ValueType2;
00592       typedef typename iterator_traits<_BI1>::iterator_category _Category;
00593       const bool __simple = (__is_pod(_ValueType1)
00594                          && __is_pointer<_BI1>::__value
00595                          && __is_pointer<_BI2>::__value
00596                  && __are_same<_ValueType1, _ValueType2>::__value);
00597 
00598       return std::__copy_move_backward<_IsMove, __simple,
00599                                    _Category>::__copy_move_b(__first,
00600                                  __last,
00601                                  __result);
00602     }
00603 
00604   template<bool _IsMove, typename _BI1, typename _BI2>
00605     inline _BI2
00606     __copy_move_backward_a2(_BI1 __first, _BI1 __last, _BI2 __result)
00607     {
00608       return _BI2(std::__copy_move_backward_a<_IsMove>
00609           (std::__niter_base(__first), std::__niter_base(__last),
00610            std::__niter_base(__result)));
00611     }
00612 
00613   /**
00614    *  @brief Copies the range [first,last) into result.
00615    *  @ingroup mutating_algorithms
00616    *  @param  first  A bidirectional iterator.
00617    *  @param  last   A bidirectional iterator.
00618    *  @param  result A bidirectional iterator.
00619    *  @return   result - (first - last)
00620    *
00621    *  The function has the same effect as copy, but starts at the end of the
00622    *  range and works its way to the start, returning the start of the result.
00623    *  This inline function will boil down to a call to @c memmove whenever
00624    *  possible.  Failing that, if random access iterators are passed, then the
00625    *  loop count will be known (and therefore a candidate for compiler
00626    *  optimizations such as unrolling).
00627    *
00628    *  Result may not be in the range [first,last).  Use copy instead.  Note
00629    *  that the start of the output range may overlap [first,last).
00630   */
00631   template<typename _BI1, typename _BI2>
00632     inline _BI2
00633     copy_backward(_BI1 __first, _BI1 __last, _BI2 __result)
00634     {
00635       // concept requirements
00636       __glibcxx_function_requires(_BidirectionalIteratorConcept<_BI1>)
00637       __glibcxx_function_requires(_Mutable_BidirectionalIteratorConcept<_BI2>)
00638       __glibcxx_function_requires(_ConvertibleConcept<
00639         typename iterator_traits<_BI1>::value_type,
00640         typename iterator_traits<_BI2>::value_type>)
00641       __glibcxx_requires_valid_range(__first, __last);
00642 
00643       return (std::__copy_move_backward_a2<__is_move_iterator<_BI1>::__value>
00644           (std::__miter_base(__first), std::__miter_base(__last),
00645            __result));
00646     }
00647 
00648 #ifdef __GXX_EXPERIMENTAL_CXX0X__
00649   /**
00650    *  @brief Moves the range [first,last) into result.
00651    *  @ingroup mutating_algorithms
00652    *  @param  first  A bidirectional iterator.
00653    *  @param  last   A bidirectional iterator.
00654    *  @param  result A bidirectional iterator.
00655    *  @return   result - (first - last)
00656    *
00657    *  The function has the same effect as move, but starts at the end of the
00658    *  range and works its way to the start, returning the start of the result.
00659    *  This inline function will boil down to a call to @c memmove whenever
00660    *  possible.  Failing that, if random access iterators are passed, then the
00661    *  loop count will be known (and therefore a candidate for compiler
00662    *  optimizations such as unrolling).
00663    *
00664    *  Result may not be in the range [first,last).  Use move instead.  Note
00665    *  that the start of the output range may overlap [first,last).
00666   */
00667   template<typename _BI1, typename _BI2>
00668     inline _BI2
00669     move_backward(_BI1 __first, _BI1 __last, _BI2 __result)
00670     {
00671       // concept requirements
00672       __glibcxx_function_requires(_BidirectionalIteratorConcept<_BI1>)
00673       __glibcxx_function_requires(_Mutable_BidirectionalIteratorConcept<_BI2>)
00674       __glibcxx_function_requires(_ConvertibleConcept<
00675         typename iterator_traits<_BI1>::value_type,
00676         typename iterator_traits<_BI2>::value_type>)
00677       __glibcxx_requires_valid_range(__first, __last);
00678 
00679       return std::__copy_move_backward_a2<true>(std::__miter_base(__first),
00680                         std::__miter_base(__last),
00681                         __result);
00682     }
00683 
00684 #define _GLIBCXX_MOVE_BACKWARD3(_Tp, _Up, _Vp) std::move_backward(_Tp, _Up, _Vp)
00685 #else
00686 #define _GLIBCXX_MOVE_BACKWARD3(_Tp, _Up, _Vp) std::copy_backward(_Tp, _Up, _Vp)
00687 #endif
00688 
00689   template<typename _ForwardIterator, typename _Tp>
00690     inline typename
00691     __gnu_cxx::__enable_if<!__is_scalar<_Tp>::__value, void>::__type
00692     __fill_a(_ForwardIterator __first, _ForwardIterator __last,
00693          const _Tp& __value)
00694     {
00695       for (; __first != __last; ++__first)
00696     *__first = __value;
00697     }
00698     
00699   template<typename _ForwardIterator, typename _Tp>
00700     inline typename
00701     __gnu_cxx::__enable_if<__is_scalar<_Tp>::__value, void>::__type
00702     __fill_a(_ForwardIterator __first, _ForwardIterator __last,
00703          const _Tp& __value)
00704     {
00705       const _Tp __tmp = __value;
00706       for (; __first != __last; ++__first)
00707     *__first = __tmp;
00708     }
00709 
00710   // Specialization: for char types we can use memset.
00711   template<typename _Tp>
00712     inline typename
00713     __gnu_cxx::__enable_if<__is_byte<_Tp>::__value, void>::__type
00714     __fill_a(_Tp* __first, _Tp* __last, const _Tp& __c)
00715     {
00716       const _Tp __tmp = __c;
00717       __builtin_memset(__first, static_cast<unsigned char>(__tmp),
00718                __last - __first);
00719     }
00720 
00721   /**
00722    *  @brief Fills the range [first,last) with copies of value.
00723    *  @ingroup mutating_algorithms
00724    *  @param  first  A forward iterator.
00725    *  @param  last   A forward iterator.
00726    *  @param  value  A reference-to-const of arbitrary type.
00727    *  @return   Nothing.
00728    *
00729    *  This function fills a range with copies of the same value.  For char
00730    *  types filling contiguous areas of memory, this becomes an inline call
00731    *  to @c memset or @c wmemset.
00732   */
00733   template<typename _ForwardIterator, typename _Tp>
00734     inline void
00735     fill(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value)
00736     {
00737       // concept requirements
00738       __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
00739                   _ForwardIterator>)
00740       __glibcxx_requires_valid_range(__first, __last);
00741 
00742       std::__fill_a(std::__niter_base(__first), std::__niter_base(__last),
00743             __value);
00744     }
00745 
00746   template<typename _OutputIterator, typename _Size, typename _Tp>
00747     inline typename
00748     __gnu_cxx::__enable_if<!__is_scalar<_Tp>::__value, _OutputIterator>::__type
00749     __fill_n_a(_OutputIterator __first, _Size __n, const _Tp& __value)
00750     {
00751       for (; __n > 0; --__n, ++__first)
00752     *__first = __value;
00753       return __first;
00754     }
00755 
00756   template<typename _OutputIterator, typename _Size, typename _Tp>
00757     inline typename
00758     __gnu_cxx::__enable_if<__is_scalar<_Tp>::__value, _OutputIterator>::__type
00759     __fill_n_a(_OutputIterator __first, _Size __n, const _Tp& __value)
00760     {
00761       const _Tp __tmp = __value;
00762       for (; __n > 0; --__n, ++__first)
00763     *__first = __tmp;
00764       return __first;
00765     }
00766 
00767   template<typename _Size, typename _Tp>
00768     inline typename
00769     __gnu_cxx::__enable_if<__is_byte<_Tp>::__value, _Tp*>::__type
00770     __fill_n_a(_Tp* __first, _Size __n, const _Tp& __c)
00771     {
00772       std::__fill_a(__first, __first + __n, __c);
00773       return __first + __n;
00774     }
00775 
00776   /**
00777    *  @brief Fills the range [first,first+n) with copies of value.
00778    *  @ingroup mutating_algorithms
00779    *  @param  first  An output iterator.
00780    *  @param  n      The count of copies to perform.
00781    *  @param  value  A reference-to-const of arbitrary type.
00782    *  @return   The iterator at first+n.
00783    *
00784    *  This function fills a range with copies of the same value.  For char
00785    *  types filling contiguous areas of memory, this becomes an inline call
00786    *  to @c memset or @ wmemset.
00787    *
00788    *  _GLIBCXX_RESOLVE_LIB_DEFECTS
00789    *  DR 865. More algorithms that throw away information
00790   */
00791   template<typename _OI, typename _Size, typename _Tp>
00792     inline _OI
00793     fill_n(_OI __first, _Size __n, const _Tp& __value)
00794     {
00795       // concept requirements
00796       __glibcxx_function_requires(_OutputIteratorConcept<_OI, _Tp>)
00797 
00798       return _OI(std::__fill_n_a(std::__niter_base(__first), __n, __value));
00799     }
00800 
00801   template<bool _BoolType>
00802     struct __equal
00803     {
00804       template<typename _II1, typename _II2>
00805         static bool
00806         equal(_II1 __first1, _II1 __last1, _II2 __first2)
00807         {
00808       for (; __first1 != __last1; ++__first1, ++__first2)
00809         if (!(*__first1 == *__first2))
00810           return false;
00811       return true;
00812     }
00813     };
00814 
00815   template<>
00816     struct __equal<true>
00817     {
00818       template<typename _Tp>
00819         static bool
00820         equal(const _Tp* __first1, const _Tp* __last1, const _Tp* __first2)
00821         {
00822       return !__builtin_memcmp(__first1, __first2, sizeof(_Tp)
00823                    * (__last1 - __first1));
00824     }
00825     };
00826 
00827   template<typename _II1, typename _II2>
00828     inline bool
00829     __equal_aux(_II1 __first1, _II1 __last1, _II2 __first2)
00830     {
00831       typedef typename iterator_traits<_II1>::value_type _ValueType1;
00832       typedef typename iterator_traits<_II2>::value_type _ValueType2;
00833       const bool __simple = (__is_integer<_ValueType1>::__value
00834                          && __is_pointer<_II1>::__value
00835                          && __is_pointer<_II2>::__value
00836                  && __are_same<_ValueType1, _ValueType2>::__value);
00837 
00838       return std::__equal<__simple>::equal(__first1, __last1, __first2);
00839     }
00840 
00841 
00842   template<typename, typename>
00843     struct __lc_rai
00844     {
00845       template<typename _II1, typename _II2>
00846         static _II1
00847         __newlast1(_II1, _II1 __last1, _II2, _II2)
00848         { return __last1; }
00849 
00850       template<typename _II>
00851         static bool
00852         __cnd2(_II __first, _II __last)
00853         { return __first != __last; }
00854     };
00855 
00856   template<>
00857     struct __lc_rai<random_access_iterator_tag, random_access_iterator_tag>
00858     {
00859       template<typename _RAI1, typename _RAI2>
00860         static _RAI1
00861         __newlast1(_RAI1 __first1, _RAI1 __last1,
00862            _RAI2 __first2, _RAI2 __last2)
00863         {
00864       const typename iterator_traits<_RAI1>::difference_type
00865         __diff1 = __last1 - __first1;
00866       const typename iterator_traits<_RAI2>::difference_type
00867         __diff2 = __last2 - __first2;
00868       return __diff2 < __diff1 ? __first1 + __diff2 : __last1;
00869     }
00870 
00871       template<typename _RAI>
00872         static bool
00873         __cnd2(_RAI, _RAI)
00874         { return true; }
00875     };
00876 
00877   template<bool _BoolType>
00878     struct __lexicographical_compare
00879     {
00880       template<typename _II1, typename _II2>
00881         static bool __lc(_II1, _II1, _II2, _II2);
00882     };
00883 
00884   template<bool _BoolType>
00885     template<typename _II1, typename _II2>
00886       bool
00887       __lexicographical_compare<_BoolType>::
00888       __lc(_II1 __first1, _II1 __last1, _II2 __first2, _II2 __last2)
00889       {
00890     typedef typename iterator_traits<_II1>::iterator_category _Category1;
00891     typedef typename iterator_traits<_II2>::iterator_category _Category2;
00892     typedef std::__lc_rai<_Category1, _Category2>   __rai_type;
00893     
00894     __last1 = __rai_type::__newlast1(__first1, __last1,
00895                      __first2, __last2);
00896     for (; __first1 != __last1 && __rai_type::__cnd2(__first2, __last2);
00897          ++__first1, ++__first2)
00898       {
00899         if (*__first1 < *__first2)
00900           return true;
00901         if (*__first2 < *__first1)
00902           return false;
00903       }
00904     return __first1 == __last1 && __first2 != __last2;
00905       }
00906 
00907   template<>
00908     struct __lexicographical_compare<true>
00909     {
00910       template<typename _Tp, typename _Up>
00911         static bool
00912         __lc(const _Tp* __first1, const _Tp* __last1,
00913          const _Up* __first2, const _Up* __last2)
00914     {
00915       const size_t __len1 = __last1 - __first1;
00916       const size_t __len2 = __last2 - __first2;
00917       const int __result = __builtin_memcmp(__first1, __first2,
00918                         std::min(__len1, __len2));
00919       return __result != 0 ? __result < 0 : __len1 < __len2;
00920     }
00921     };
00922 
00923   template<typename _II1, typename _II2>
00924     inline bool
00925     __lexicographical_compare_aux(_II1 __first1, _II1 __last1,
00926                   _II2 __first2, _II2 __last2)
00927     {
00928       typedef typename iterator_traits<_II1>::value_type _ValueType1;
00929       typedef typename iterator_traits<_II2>::value_type _ValueType2;
00930       const bool __simple =
00931     (__is_byte<_ValueType1>::__value && __is_byte<_ValueType2>::__value
00932      && !__gnu_cxx::__numeric_traits<_ValueType1>::__is_signed
00933      && !__gnu_cxx::__numeric_traits<_ValueType2>::__is_signed
00934      && __is_pointer<_II1>::__value
00935      && __is_pointer<_II2>::__value);
00936 
00937       return std::__lexicographical_compare<__simple>::__lc(__first1, __last1,
00938                                 __first2, __last2);
00939     }
00940 
00941   /**
00942    *  @brief Finds the first position in which @a val could be inserted
00943    *         without changing the ordering.
00944    *  @param  first   An iterator.
00945    *  @param  last    Another iterator.
00946    *  @param  val     The search term.
00947    *  @return         An iterator pointing to the first element <em>not less
00948    *                  than</em> @a val, or end() if every element is less than 
00949    *                  @a val.
00950    *  @ingroup binary_search_algorithms
00951   */
00952   template<typename _ForwardIterator, typename _Tp>
00953     _ForwardIterator
00954     lower_bound(_ForwardIterator __first, _ForwardIterator __last,
00955         const _Tp& __val)
00956     {
00957       typedef typename iterator_traits<_ForwardIterator>::value_type
00958     _ValueType;
00959       typedef typename iterator_traits<_ForwardIterator>::difference_type
00960     _DistanceType;
00961 
00962       // concept requirements
00963       __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
00964       __glibcxx_function_requires(_LessThanOpConcept<_ValueType, _Tp>)
00965       __glibcxx_requires_partitioned_lower(__first, __last, __val);
00966 
00967       _DistanceType __len = std::distance(__first, __last);
00968       _DistanceType __half;
00969       _ForwardIterator __middle;
00970 
00971       while (__len > 0)
00972     {
00973       __half = __len >> 1;
00974       __middle = __first;
00975       std::advance(__middle, __half);
00976       if (*__middle < __val)
00977         {
00978           __first = __middle;
00979           ++__first;
00980           __len = __len - __half - 1;
00981         }
00982       else
00983         __len = __half;
00984     }
00985       return __first;
00986     }
00987 
00988   /// This is a helper function for the sort routines and for random.tcc.
00989   //  Precondition: __n > 0.
00990   template<typename _Size>
00991     inline _Size
00992     __lg(_Size __n)
00993     {
00994       _Size __k;
00995       for (__k = 0; __n != 0; __n >>= 1)
00996     ++__k;
00997       return __k - 1;
00998     }
00999 
01000   inline int
01001   __lg(int __n)
01002   { return sizeof(int) * __CHAR_BIT__  - 1 - __builtin_clz(__n); }
01003 
01004   inline long
01005   __lg(long __n)
01006   { return sizeof(long) * __CHAR_BIT__ - 1 - __builtin_clzl(__n); }
01007 
01008   inline long long
01009   __lg(long long __n)
01010   { return sizeof(long long) * __CHAR_BIT__ - 1 - __builtin_clzll(__n); }
01011 
01012 _GLIBCXX_END_NAMESPACE
01013 
01014 _GLIBCXX_BEGIN_NESTED_NAMESPACE(std, _GLIBCXX_STD_P)
01015 
01016   /**
01017    *  @brief Tests a range for element-wise equality.
01018    *  @ingroup non_mutating_algorithms
01019    *  @param  first1  An input iterator.
01020    *  @param  last1   An input iterator.
01021    *  @param  first2  An input iterator.
01022    *  @return   A boolean true or false.
01023    *
01024    *  This compares the elements of two ranges using @c == and returns true or
01025    *  false depending on whether all of the corresponding elements of the
01026    *  ranges are equal.
01027   */
01028   template<typename _II1, typename _II2>
01029     inline bool
01030     equal(_II1 __first1, _II1 __last1, _II2 __first2)
01031     {
01032       // concept requirements
01033       __glibcxx_function_requires(_InputIteratorConcept<_II1>)
01034       __glibcxx_function_requires(_InputIteratorConcept<_II2>)
01035       __glibcxx_function_requires(_EqualOpConcept<
01036         typename iterator_traits<_II1>::value_type,
01037         typename iterator_traits<_II2>::value_type>)
01038       __glibcxx_requires_valid_range(__first1, __last1);
01039 
01040       return std::__equal_aux(std::__niter_base(__first1),
01041                   std::__niter_base(__last1),
01042                   std::__niter_base(__first2));
01043     }
01044 
01045   /**
01046    *  @brief Tests a range for element-wise equality.
01047    *  @ingroup non_mutating_algorithms
01048    *  @param  first1  An input iterator.
01049    *  @param  last1   An input iterator.
01050    *  @param  first2  An input iterator.
01051    *  @param binary_pred A binary predicate @link functors
01052    *                  functor@endlink.
01053    *  @return         A boolean true or false.
01054    *
01055    *  This compares the elements of two ranges using the binary_pred
01056    *  parameter, and returns true or
01057    *  false depending on whether all of the corresponding elements of the
01058    *  ranges are equal.
01059   */
01060   template<typename _IIter1, typename _IIter2, typename _BinaryPredicate>
01061     inline bool
01062     equal(_IIter1 __first1, _IIter1 __last1,
01063       _IIter2 __first2, _BinaryPredicate __binary_pred)
01064     {
01065       // concept requirements
01066       __glibcxx_function_requires(_InputIteratorConcept<_IIter1>)
01067       __glibcxx_function_requires(_InputIteratorConcept<_IIter2>)
01068       __glibcxx_requires_valid_range(__first1, __last1);
01069 
01070       for (; __first1 != __last1; ++__first1, ++__first2)
01071     if (!bool(__binary_pred(*__first1, *__first2)))
01072       return false;
01073       return true;
01074     }
01075 
01076   /**
01077    *  @brief Performs @b dictionary comparison on ranges.
01078    *  @ingroup sorting_algorithms
01079    *  @param  first1  An input iterator.
01080    *  @param  last1   An input iterator.
01081    *  @param  first2  An input iterator.
01082    *  @param  last2   An input iterator.
01083    *  @return   A boolean true or false.
01084    *
01085    *  <em>Returns true if the sequence of elements defined by the range
01086    *  [first1,last1) is lexicographically less than the sequence of elements
01087    *  defined by the range [first2,last2).  Returns false otherwise.</em>
01088    *  (Quoted from [25.3.8]/1.)  If the iterators are all character pointers,
01089    *  then this is an inline call to @c memcmp.
01090   */
01091   template<typename _II1, typename _II2>
01092     inline bool
01093     lexicographical_compare(_II1 __first1, _II1 __last1,
01094                 _II2 __first2, _II2 __last2)
01095     {
01096       // concept requirements
01097       typedef typename iterator_traits<_II1>::value_type _ValueType1;
01098       typedef typename iterator_traits<_II2>::value_type _ValueType2;
01099       __glibcxx_function_requires(_InputIteratorConcept<_II1>)
01100       __glibcxx_function_requires(_InputIteratorConcept<_II2>)
01101       __glibcxx_function_requires(_LessThanOpConcept<_ValueType1, _ValueType2>)
01102       __glibcxx_function_requires(_LessThanOpConcept<_ValueType2, _ValueType1>)
01103       __glibcxx_requires_valid_range(__first1, __last1);
01104       __glibcxx_requires_valid_range(__first2, __last2);
01105 
01106       return std::__lexicographical_compare_aux(std::__niter_base(__first1),
01107                         std::__niter_base(__last1),
01108                         std::__niter_base(__first2),
01109                         std::__niter_base(__last2));
01110     }
01111 
01112   /**
01113    *  @brief Performs @b dictionary comparison on ranges.
01114    *  @ingroup sorting_algorithms
01115    *  @param  first1  An input iterator.
01116    *  @param  last1   An input iterator.
01117    *  @param  first2  An input iterator.
01118    *  @param  last2   An input iterator.
01119    *  @param  comp  A @link comparison_functors comparison functor@endlink.
01120    *  @return   A boolean true or false.
01121    *
01122    *  The same as the four-parameter @c lexicographical_compare, but uses the
01123    *  comp parameter instead of @c <.
01124   */
01125   template<typename _II1, typename _II2, typename _Compare>
01126     bool
01127     lexicographical_compare(_II1 __first1, _II1 __last1,
01128                 _II2 __first2, _II2 __last2, _Compare __comp)
01129     {
01130       typedef typename iterator_traits<_II1>::iterator_category _Category1;
01131       typedef typename iterator_traits<_II2>::iterator_category _Category2;
01132       typedef std::__lc_rai<_Category1, _Category2>     __rai_type;
01133 
01134       // concept requirements
01135       __glibcxx_function_requires(_InputIteratorConcept<_II1>)
01136       __glibcxx_function_requires(_InputIteratorConcept<_II2>)
01137       __glibcxx_requires_valid_range(__first1, __last1);
01138       __glibcxx_requires_valid_range(__first2, __last2);
01139 
01140       __last1 = __rai_type::__newlast1(__first1, __last1, __first2, __last2);
01141       for (; __first1 != __last1 && __rai_type::__cnd2(__first2, __last2);
01142        ++__first1, ++__first2)
01143     {
01144       if (__comp(*__first1, *__first2))
01145         return true;
01146       if (__comp(*__first2, *__first1))
01147         return false;
01148     }
01149       return __first1 == __last1 && __first2 != __last2;
01150     }
01151 
01152   /**
01153    *  @brief Finds the places in ranges which don't match.
01154    *  @ingroup non_mutating_algorithms
01155    *  @param  first1  An input iterator.
01156    *  @param  last1   An input iterator.
01157    *  @param  first2  An input iterator.
01158    *  @return   A pair of iterators pointing to the first mismatch.
01159    *
01160    *  This compares the elements of two ranges using @c == and returns a pair
01161    *  of iterators.  The first iterator points into the first range, the
01162    *  second iterator points into the second range, and the elements pointed
01163    *  to by the iterators are not equal.
01164   */
01165   template<typename _InputIterator1, typename _InputIterator2>
01166     pair<_InputIterator1, _InputIterator2>
01167     mismatch(_InputIterator1 __first1, _InputIterator1 __last1,
01168          _InputIterator2 __first2)
01169     {
01170       // concept requirements
01171       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
01172       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
01173       __glibcxx_function_requires(_EqualOpConcept<
01174         typename iterator_traits<_InputIterator1>::value_type,
01175         typename iterator_traits<_InputIterator2>::value_type>)
01176       __glibcxx_requires_valid_range(__first1, __last1);
01177 
01178       while (__first1 != __last1 && *__first1 == *__first2)
01179         {
01180       ++__first1;
01181       ++__first2;
01182         }
01183       return pair<_InputIterator1, _InputIterator2>(__first1, __first2);
01184     }
01185 
01186   /**
01187    *  @brief Finds the places in ranges which don't match.
01188    *  @ingroup non_mutating_algorithms
01189    *  @param  first1  An input iterator.
01190    *  @param  last1   An input iterator.
01191    *  @param  first2  An input iterator.
01192    *  @param binary_pred A binary predicate @link functors
01193    *         functor@endlink.
01194    *  @return   A pair of iterators pointing to the first mismatch.
01195    *
01196    *  This compares the elements of two ranges using the binary_pred
01197    *  parameter, and returns a pair
01198    *  of iterators.  The first iterator points into the first range, the
01199    *  second iterator points into the second range, and the elements pointed
01200    *  to by the iterators are not equal.
01201   */
01202   template<typename _InputIterator1, typename _InputIterator2,
01203        typename _BinaryPredicate>
01204     pair<_InputIterator1, _InputIterator2>
01205     mismatch(_InputIterator1 __first1, _InputIterator1 __last1,
01206          _InputIterator2 __first2, _BinaryPredicate __binary_pred)
01207     {
01208       // concept requirements
01209       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
01210       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
01211       __glibcxx_requires_valid_range(__first1, __last1);
01212 
01213       while (__first1 != __last1 && bool(__binary_pred(*__first1, *__first2)))
01214         {
01215       ++__first1;
01216       ++__first2;
01217         }
01218       return pair<_InputIterator1, _InputIterator2>(__first1, __first2);
01219     }
01220 
01221 _GLIBCXX_END_NESTED_NAMESPACE
01222 
01223 // NB: This file is included within many other C++ includes, as a way
01224 // of getting the base algorithms. So, make sure that parallel bits
01225 // come in too if requested. 
01226 #ifdef _GLIBCXX_PARALLEL
01227 # include <parallel/algobase.h>
01228 #endif
01229 
01230 #endif