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  _LIBCPP_HIDE_FROM_ABI constexpr static _Iter
42  __partition_point_fn_impl(_Iter&& __first, _Sent&& __last, _Pred& __pred, _Proj& __proj) {
43    auto __len = ranges::distance(__first, __last);
44
45    while (__len != 0) {
46      auto __half_len = std::__half_positive(__len);
47      auto __mid      = ranges::next(__first, __half_len);
48
49      if (std::invoke(__pred, std::invoke(__proj, *__mid))) {
50        __first = ++__mid;
51        __len -= __half_len + 1;
52
53      } else {
54        __len = __half_len;
55      }
56    }
57
58    return __first;
59  }
60
61  template <forward_iterator _Iter,
62            sentinel_for<_Iter> _Sent,
63            class _Proj = identity,
64            indirect_unary_predicate<projected<_Iter, _Proj>> _Pred>
65  _LIBCPP_HIDE_FROM_ABI constexpr _Iter operator()(_Iter __first, _Sent __last, _Pred __pred, _Proj __proj = {}) const {
66    return __partition_point_fn_impl(std::move(__first), std::move(__last), __pred, __proj);
67  }
68
69  template <forward_range _Range,
70            class _Proj = identity,
71            indirect_unary_predicate<projected<iterator_t<_Range>, _Proj>> _Pred>
72  _LIBCPP_HIDE_FROM_ABI constexpr borrowed_iterator_t<_Range>
73  operator()(_Range&& __range, _Pred __pred, _Proj __proj = {}) const {
74    return __partition_point_fn_impl(ranges::begin(__range), ranges::end(__range), __pred, __proj);
75  }
76};
77
78inline namespace __cpo {
79inline constexpr auto partition_point = __partition_point{};
80} // namespace __cpo
81} // namespace ranges
82
83_LIBCPP_END_NAMESPACE_STD
84
85#endif // _LIBCPP_STD_VER >= 20
86
87_LIBCPP_POP_MACROS
88
89#endif // _LIBCPP___ALGORITHM_RANGES_PARTITION_POINT_H