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 <__type_traits/remove_cvref.h>
16#include <__utility/move.h>
17#include <__utility/pair.h>
18
19#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
20#  pragma GCC system_header
21#endif
22
23_LIBCPP_PUSH_MACROS
24#include <__undef_macros>
25
26_LIBCPP_BEGIN_NAMESPACE_STD
27
28template <class _Predicate, class _AlgPolicy, class _ForwardIterator, class _Sentinel>
29_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_ForwardIterator, _ForwardIterator>
30__partition_impl(_ForwardIterator __first, _Sentinel __last, _Predicate __pred, forward_iterator_tag) {
31  while (true) {
32    if (__first == __last)
33      return std::make_pair(__first, __first);
34    if (!__pred(*__first))
35      break;
36    ++__first;
37  }
38
39  _ForwardIterator __p = __first;
40  while (++__p != __last) {
41    if (__pred(*__p)) {
42      _IterOps<_AlgPolicy>::iter_swap(__first, __p);
43      ++__first;
44    }
45  }
46  return std::make_pair(std::move(__first), std::move(__p));
47}
48
49template <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, bidirectional_iterator_tag) {
52  _BidirectionalIterator __original_last = _IterOps<_AlgPolicy>::next(__first, __sentinel);
53  _BidirectionalIterator __last          = __original_last;
54
55  while (true) {
56    while (true) {
57      if (__first == __last)
58        return std::make_pair(std::move(__first), std::move(__original_last));
59      if (!__pred(*__first))
60        break;
61      ++__first;
62    }
63    do {
64      if (__first == --__last)
65        return std::make_pair(std::move(__first), std::move(__original_last));
66    } while (!__pred(*__last));
67    _IterOps<_AlgPolicy>::iter_swap(__first, __last);
68    ++__first;
69  }
70}
71
72template <class _AlgPolicy, class _ForwardIterator, class _Sentinel, class _Predicate, class _IterCategory>
73inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_ForwardIterator, _ForwardIterator>
74__partition(_ForwardIterator __first, _Sentinel __last, _Predicate&& __pred, _IterCategory __iter_category) {
75  return std::__partition_impl<__remove_cvref_t<_Predicate>&, _AlgPolicy>(
76      std::move(__first), std::move(__last), __pred, __iter_category);
77}
78
79template <class _ForwardIterator, class _Predicate>
80inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
81partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
82  using _IterCategory = typename iterator_traits<_ForwardIterator>::iterator_category;
83  auto __result = std::__partition<_ClassicAlgPolicy>(std::move(__first), std::move(__last), __pred, _IterCategory());
84  return __result.first;
85}
86
87_LIBCPP_END_NAMESPACE_STD
88
89_LIBCPP_POP_MACROS
90
91#endif // _LIBCPP___ALGORITHM_PARTITION_H