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1 //===----------------------------------------------------------------------===//
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2 //
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3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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4 // See https://llvm.org/LICENSE.txt for license information.
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5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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6 //
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7 //===----------------------------------------------------------------------===//
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8
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9 #ifndef _LIBCPP___ALGORITHM_STABLE_PARTITION_H
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10 #define _LIBCPP___ALGORITHM_STABLE_PARTITION_H
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11
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236
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12 #include <__algorithm/iterator_operations.h>
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13 #include <__algorithm/rotate.h>
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221
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14 #include <__config>
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236
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15 #include <__iterator/advance.h>
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16 #include <__iterator/distance.h>
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221
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17 #include <__iterator/iterator_traits.h>
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236
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18 #include <__memory/destruct_n.h>
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19 #include <__memory/temporary_buffer.h>
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20 #include <__memory/unique_ptr.h>
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21 #include <__utility/move.h>
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22 #include <__utility/pair.h>
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23 #include <new>
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24 #include <type_traits>
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221
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25
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26 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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236
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27 # pragma GCC system_header
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221
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28 #endif
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29
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30 _LIBCPP_BEGIN_NAMESPACE_STD
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31
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236
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32 template <class _AlgPolicy, class _Predicate, class _ForwardIterator, class _Distance, class _Pair>
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33 _LIBCPP_HIDE_FROM_ABI _ForwardIterator
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34 __stable_partition_impl(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred,
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221
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35 _Distance __len, _Pair __p, forward_iterator_tag __fit)
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36 {
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236
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37 using _Ops = _IterOps<_AlgPolicy>;
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38
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221
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39 // *__first is known to be false
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40 // __len >= 1
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41 if (__len == 1)
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42 return __first;
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43 if (__len == 2)
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44 {
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45 _ForwardIterator __m = __first;
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46 if (__pred(*++__m))
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47 {
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236
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48 _Ops::iter_swap(__first, __m);
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221
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49 return __m;
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50 }
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51 return __first;
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52 }
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53 if (__len <= __p.second)
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54 { // The buffer is big enough to use
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55 typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
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56 __destruct_n __d(0);
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57 unique_ptr<value_type, __destruct_n&> __h(__p.first, __d);
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58 // Move the falses into the temporary buffer, and the trues to the front of the line
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59 // Update __first to always point to the end of the trues
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60 value_type* __t = __p.first;
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236
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61 ::new ((void*)__t) value_type(_Ops::__iter_move(__first));
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221
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62 __d.template __incr<value_type>();
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63 ++__t;
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64 _ForwardIterator __i = __first;
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65 while (++__i != __last)
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66 {
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67 if (__pred(*__i))
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68 {
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236
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69 *__first = _Ops::__iter_move(__i);
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221
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70 ++__first;
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71 }
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72 else
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73 {
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236
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74 ::new ((void*)__t) value_type(_Ops::__iter_move(__i));
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221
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75 __d.template __incr<value_type>();
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76 ++__t;
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77 }
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78 }
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79 // All trues now at start of range, all falses in buffer
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80 // Move falses back into range, but don't mess up __first which points to first false
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81 __i = __first;
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82 for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, (void) ++__i)
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236
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83 *__i = _Ops::__iter_move(__t2);
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221
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84 // __h destructs moved-from values out of the temp buffer, but doesn't deallocate buffer
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85 return __first;
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86 }
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87 // Else not enough buffer, do in place
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88 // __len >= 3
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89 _ForwardIterator __m = __first;
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90 _Distance __len2 = __len / 2; // __len2 >= 2
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236
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91 _Ops::advance(__m, __len2);
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221
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92 // recurse on [__first, __m), *__first know to be false
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93 // F?????????????????
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94 // f m l
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236
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95 _ForwardIterator __first_false = std::__stable_partition_impl<_AlgPolicy, _Predicate&>(
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96 __first, __m, __pred, __len2, __p, __fit);
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221
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97 // TTTFFFFF??????????
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98 // f ff m l
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99 // recurse on [__m, __last], except increase __m until *(__m) is false, *__last know to be true
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100 _ForwardIterator __m1 = __m;
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101 _ForwardIterator __second_false = __last;
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102 _Distance __len_half = __len - __len2;
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103 while (__pred(*__m1))
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104 {
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105 if (++__m1 == __last)
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106 goto __second_half_done;
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107 --__len_half;
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108 }
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109 // TTTFFFFFTTTF??????
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110 // f ff m m1 l
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236
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111 __second_false = std::__stable_partition_impl<_AlgPolicy, _Predicate&>(
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112 __m1, __last, __pred, __len_half, __p, __fit);
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221
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113 __second_half_done:
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114 // TTTFFFFFTTTTTFFFFF
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115 // f ff m sf l
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236
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116 return std::__rotate<_AlgPolicy>(__first_false, __m, __second_false).first;
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221
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117 // TTTTTTTTFFFFFFFFFF
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118 // |
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119 }
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120
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236
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121 template <class _AlgPolicy, class _Predicate, class _ForwardIterator>
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122 _LIBCPP_HIDE_FROM_ABI _ForwardIterator
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123 __stable_partition_impl(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred,
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221
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124 forward_iterator_tag)
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125 {
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126 const unsigned __alloc_limit = 3; // might want to make this a function of trivial assignment
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127 // Either prove all true and return __first or point to first false
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128 while (true)
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129 {
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130 if (__first == __last)
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131 return __first;
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132 if (!__pred(*__first))
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133 break;
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134 ++__first;
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135 }
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136 // We now have a reduced range [__first, __last)
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137 // *__first is known to be false
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138 typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
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139 typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
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236
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140 difference_type __len = _IterOps<_AlgPolicy>::distance(__first, __last);
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221
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141 pair<value_type*, ptrdiff_t> __p(0, 0);
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142 unique_ptr<value_type, __return_temporary_buffer> __h;
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143 if (__len >= __alloc_limit)
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144 {
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236
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145 // TODO: Remove the use of std::get_temporary_buffer
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146 _LIBCPP_SUPPRESS_DEPRECATED_PUSH
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221
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147 __p = _VSTD::get_temporary_buffer<value_type>(__len);
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236
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148 _LIBCPP_SUPPRESS_DEPRECATED_POP
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221
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149 __h.reset(__p.first);
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150 }
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236
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151 return std::__stable_partition_impl<_AlgPolicy, _Predicate&>(
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152 std::move(__first), std::move(__last), __pred, __len, __p, forward_iterator_tag());
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221
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153 }
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154
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236
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155 template <class _AlgPolicy, class _Predicate, class _BidirectionalIterator, class _Distance, class _Pair>
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221
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156 _BidirectionalIterator
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236
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157 __stable_partition_impl(_BidirectionalIterator __first, _BidirectionalIterator __last, _Predicate __pred,
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221
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158 _Distance __len, _Pair __p, bidirectional_iterator_tag __bit)
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159 {
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236
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160 using _Ops = _IterOps<_AlgPolicy>;
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161
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221
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162 // *__first is known to be false
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163 // *__last is known to be true
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164 // __len >= 2
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165 if (__len == 2)
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166 {
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236
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167 _Ops::iter_swap(__first, __last);
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221
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168 return __last;
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169 }
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170 if (__len == 3)
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171 {
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172 _BidirectionalIterator __m = __first;
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173 if (__pred(*++__m))
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174 {
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236
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175 _Ops::iter_swap(__first, __m);
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176 _Ops::iter_swap(__m, __last);
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221
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177 return __last;
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178 }
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236
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179 _Ops::iter_swap(__m, __last);
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180 _Ops::iter_swap(__first, __m);
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221
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181 return __m;
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182 }
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183 if (__len <= __p.second)
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184 { // The buffer is big enough to use
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185 typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
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186 __destruct_n __d(0);
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187 unique_ptr<value_type, __destruct_n&> __h(__p.first, __d);
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188 // Move the falses into the temporary buffer, and the trues to the front of the line
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189 // Update __first to always point to the end of the trues
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190 value_type* __t = __p.first;
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236
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191 ::new ((void*)__t) value_type(_Ops::__iter_move(__first));
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221
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192 __d.template __incr<value_type>();
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193 ++__t;
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194 _BidirectionalIterator __i = __first;
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195 while (++__i != __last)
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196 {
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197 if (__pred(*__i))
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198 {
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236
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199 *__first = _Ops::__iter_move(__i);
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221
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200 ++__first;
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201 }
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202 else
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203 {
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236
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204 ::new ((void*)__t) value_type(_Ops::__iter_move(__i));
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221
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205 __d.template __incr<value_type>();
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206 ++__t;
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207 }
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208 }
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209 // move *__last, known to be true
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236
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210 *__first = _Ops::__iter_move(__i);
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221
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211 __i = ++__first;
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212 // All trues now at start of range, all falses in buffer
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213 // Move falses back into range, but don't mess up __first which points to first false
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214 for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, (void) ++__i)
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236
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215 *__i = _Ops::__iter_move(__t2);
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221
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216 // __h destructs moved-from values out of the temp buffer, but doesn't deallocate buffer
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217 return __first;
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218 }
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219 // Else not enough buffer, do in place
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220 // __len >= 4
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221 _BidirectionalIterator __m = __first;
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222 _Distance __len2 = __len / 2; // __len2 >= 2
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236
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223 _Ops::advance(__m, __len2);
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221
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224 // recurse on [__first, __m-1], except reduce __m-1 until *(__m-1) is true, *__first know to be false
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225 // F????????????????T
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226 // f m l
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227 _BidirectionalIterator __m1 = __m;
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228 _BidirectionalIterator __first_false = __first;
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229 _Distance __len_half = __len2;
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230 while (!__pred(*--__m1))
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231 {
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232 if (__m1 == __first)
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233 goto __first_half_done;
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234 --__len_half;
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235 }
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236 // F???TFFF?????????T
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237 // f m1 m l
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236
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238 __first_false = std::__stable_partition_impl<_AlgPolicy, _Predicate&>(
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239 __first, __m1, __pred, __len_half, __p, __bit);
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221
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240 __first_half_done:
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241 // TTTFFFFF?????????T
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242 // f ff m l
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243 // recurse on [__m, __last], except increase __m until *(__m) is false, *__last know to be true
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244 __m1 = __m;
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245 _BidirectionalIterator __second_false = __last;
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246 ++__second_false;
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247 __len_half = __len - __len2;
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248 while (__pred(*__m1))
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249 {
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250 if (++__m1 == __last)
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251 goto __second_half_done;
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252 --__len_half;
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253 }
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254 // TTTFFFFFTTTF?????T
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255 // f ff m m1 l
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236
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256 __second_false = std::__stable_partition_impl<_AlgPolicy, _Predicate&>(
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257 __m1, __last, __pred, __len_half, __p, __bit);
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221
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258 __second_half_done:
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259 // TTTFFFFFTTTTTFFFFF
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260 // f ff m sf l
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236
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261 return std::__rotate<_AlgPolicy>(__first_false, __m, __second_false).first;
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221
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262 // TTTTTTTTFFFFFFFFFF
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263 // |
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264 }
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265
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236
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266 template <class _AlgPolicy, class _Predicate, class _BidirectionalIterator>
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267 _LIBCPP_HIDE_FROM_ABI _BidirectionalIterator
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268 __stable_partition_impl(_BidirectionalIterator __first, _BidirectionalIterator __last, _Predicate __pred,
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221
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269 bidirectional_iterator_tag)
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270 {
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271 typedef typename iterator_traits<_BidirectionalIterator>::difference_type difference_type;
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272 typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
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273 const difference_type __alloc_limit = 4; // might want to make this a function of trivial assignment
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274 // Either prove all true and return __first or point to first false
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275 while (true)
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276 {
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277 if (__first == __last)
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278 return __first;
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279 if (!__pred(*__first))
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280 break;
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281 ++__first;
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282 }
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283 // __first points to first false, everything prior to __first is already set.
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284 // Either prove [__first, __last) is all false and return __first, or point __last to last true
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285 do
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286 {
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287 if (__first == --__last)
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288 return __first;
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289 } while (!__pred(*__last));
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290 // We now have a reduced range [__first, __last]
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291 // *__first is known to be false
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292 // *__last is known to be true
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293 // __len >= 2
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236
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294 difference_type __len = _IterOps<_AlgPolicy>::distance(__first, __last) + 1;
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221
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295 pair<value_type*, ptrdiff_t> __p(0, 0);
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296 unique_ptr<value_type, __return_temporary_buffer> __h;
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297 if (__len >= __alloc_limit)
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298 {
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236
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299 // TODO: Remove the use of std::get_temporary_buffer
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300 _LIBCPP_SUPPRESS_DEPRECATED_PUSH
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221
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301 __p = _VSTD::get_temporary_buffer<value_type>(__len);
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236
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302 _LIBCPP_SUPPRESS_DEPRECATED_POP
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221
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303 __h.reset(__p.first);
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304 }
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236
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305 return std::__stable_partition_impl<_AlgPolicy, _Predicate&>(
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306 std::move(__first), std::move(__last), __pred, __len, __p, bidirectional_iterator_tag());
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307 }
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308
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309 template <class _AlgPolicy, class _Predicate, class _ForwardIterator, class _IterCategory>
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310 _LIBCPP_HIDE_FROM_ABI
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311 _ForwardIterator __stable_partition(
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312 _ForwardIterator __first, _ForwardIterator __last, _Predicate&& __pred, _IterCategory __iter_category) {
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313 return std::__stable_partition_impl<_AlgPolicy, __remove_cvref_t<_Predicate>&>(
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314 std::move(__first), std::move(__last), __pred, __iter_category);
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221
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315 }
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316
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317 template <class _ForwardIterator, class _Predicate>
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318 inline _LIBCPP_INLINE_VISIBILITY
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319 _ForwardIterator
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320 stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred)
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321 {
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236
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322 using _IterCategory = typename iterator_traits<_ForwardIterator>::iterator_category;
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323 return std::__stable_partition<_ClassicAlgPolicy, _Predicate&>(
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324 std::move(__first), std::move(__last), __pred, _IterCategory());
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221
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325 }
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326
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327 _LIBCPP_END_NAMESPACE_STD
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328
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329 #endif // _LIBCPP___ALGORITHM_STABLE_PARTITION_H
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