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_RANGES_PARTITION_POINT_H
10#define _LIBCPP___ALGORITHM_RANGES_PARTITION_POINT_H
11
12#include <__algorithm/half_positive.h>
13#include <__config>
14#include <__functional/identity.h>
15#include <__functional/invoke.h>
16#include <__iterator/concepts.h>
17#include <__iterator/distance.h>
18#include <__iterator/iterator_traits.h>
19#include <__iterator/next.h>
20#include <__iterator/projected.h>
21#include <__ranges/access.h>
22#include <__ranges/concepts.h>
23#include <__ranges/dangling.h>
24#include <__utility/move.h>
25
26#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
27# pragma GCC system_header
28#endif
29
30_LIBCPP_PUSH_MACROS
31#include <__undef_macros>
32
33#if _LIBCPP_STD_VER >= 20
34
35_LIBCPP_BEGIN_NAMESPACE_STD
36
37namespace ranges {
38struct __partition_point {
39 // TODO(ranges): delegate to the classic algorithm.
40 template <class _Iter, class _Sent, class _Proj, class _Pred>
41 constexpr static _Iter __partition_point_fn_impl(_Iter&& __first, _Sent&& __last, _Pred& __pred, _Proj& __proj) {
42 auto __len = ranges::distance(__first, __last);
43
44 while (__len != 0) {
45 auto __half_len = std::__half_positive(__len);
46 auto __mid = ranges::next(__first, __half_len);
47
48 if (std::invoke(__pred, std::invoke(__proj, *__mid))) {
49 __first = ++__mid;
50 __len -= __half_len + 1;
51
52 } else {
53 __len = __half_len;
54 }
55 }
56
57 return __first;
58 }
59
60 template <forward_iterator _Iter,
61 sentinel_for<_Iter> _Sent,
62 class _Proj = identity,
63 indirect_unary_predicate<projected<_Iter, _Proj>> _Pred>
64 constexpr _Iter operator()(_Iter __first, _Sent __last, _Pred __pred, _Proj __proj = {}) const {
65 return __partition_point_fn_impl(std::move(__first), std::move(__last), __pred, __proj);
66 }
67
68 template <forward_range _Range,
69 class _Proj = identity,
70 indirect_unary_predicate<projected<iterator_t<_Range>, _Proj>> _Pred>
71 constexpr borrowed_iterator_t<_Range> operator()(_Range&& __range, _Pred __pred, _Proj __proj = {}) const {
72 return __partition_point_fn_impl(ranges::begin(__range), ranges::end(__range), __pred, __proj);
73 }
74};
75
76inline namespace __cpo {
77inline constexpr auto partition_point = __partition_point{};
78} // namespace __cpo
79} // namespace ranges
80
81_LIBCPP_END_NAMESPACE_STD
82
83#endif // _LIBCPP_STD_VER >= 20
84
85_LIBCPP_POP_MACROS
86
87#endif // _LIBCPP___ALGORITHM_RANGES_PARTITION_POINT_H
88