1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef _LIBCPP___ALGORITHM_PARTITION_H
10 #define _LIBCPP___ALGORITHM_PARTITION_H
11 
12 #include <__algorithm/iterator_operations.h>
13 #include <__config>
14 #include <__iterator/iterator_traits.h>
15 #include <__utility/move.h>
16 #include <__utility/pair.h>
17 
18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
19 #  pragma GCC system_header
20 #endif
21 
22 _LIBCPP_BEGIN_NAMESPACE_STD
23 
24 template <class _Predicate, class _AlgPolicy, class _ForwardIterator, class _Sentinel>
25 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_ForwardIterator, _ForwardIterator>
26 __partition_impl(_ForwardIterator __first, _Sentinel __last, _Predicate __pred, forward_iterator_tag)
27 {
28     while (true)
29     {
30         if (__first == __last)
31             return std::make_pair(std::move(__first), std::move(__first));
32         if (!__pred(*__first))
33             break;
34         ++__first;
35     }
36 
37     _ForwardIterator __p = __first;
38     while (++__p != __last)
39     {
40         if (__pred(*__p))
41         {
42             _IterOps<_AlgPolicy>::iter_swap(__first, __p);
43             ++__first;
44         }
45     }
46     return std::make_pair(std::move(__first), std::move(__p));
47 }
48 
49 template <class _Predicate, class _AlgPolicy, class _BidirectionalIterator, class _Sentinel>
50 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator, _BidirectionalIterator>
51 __partition_impl(_BidirectionalIterator __first, _Sentinel __sentinel, _Predicate __pred,
52             bidirectional_iterator_tag)
53 {
54     _BidirectionalIterator __original_last = _IterOps<_AlgPolicy>::next(__first, __sentinel);
55     _BidirectionalIterator __last = __original_last;
56 
57     while (true)
58     {
59         while (true)
60         {
61             if (__first == __last)
62                 return std::make_pair(std::move(__first), std::move(__original_last));
63             if (!__pred(*__first))
64                 break;
65             ++__first;
66         }
67         do
68         {
69             if (__first == --__last)
70                 return std::make_pair(std::move(__first), std::move(__original_last));
71         } while (!__pred(*__last));
72         _IterOps<_AlgPolicy>::iter_swap(__first, __last);
73         ++__first;
74     }
75 }
76 
77 template <class _AlgPolicy, class _ForwardIterator, class _Sentinel, class _Predicate, class _IterCategory>
78 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
79 pair<_ForwardIterator, _ForwardIterator> __partition(
80     _ForwardIterator __first, _Sentinel __last, _Predicate&& __pred, _IterCategory __iter_category) {
81   return std::__partition_impl<__remove_cvref_t<_Predicate>&, _AlgPolicy>(
82       std::move(__first), std::move(__last), __pred, __iter_category);
83 }
84 
85 template <class _ForwardIterator, class _Predicate>
86 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
87 _ForwardIterator
88 partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred)
89 {
90   using _IterCategory = typename iterator_traits<_ForwardIterator>::iterator_category;
91   auto __result = std::__partition<_ClassicAlgPolicy>(std::move(__first), std::move(__last), __pred, _IterCategory());
92   return __result.first;
93 }
94 
95 _LIBCPP_END_NAMESPACE_STD
96 
97 #endif // _LIBCPP___ALGORITHM_PARTITION_H
98