xref: /freebsd-src/contrib/llvm-project/libcxx/include/__algorithm/ranges_partition_point.h (revision b3edf4467982447620505a28fc82e38a414c07dc)
1753f127fSDimitry Andric //===----------------------------------------------------------------------===//
2753f127fSDimitry Andric //
3753f127fSDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4753f127fSDimitry Andric // See https://llvm.org/LICENSE.txt for license information.
5753f127fSDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6753f127fSDimitry Andric //
7753f127fSDimitry Andric //===----------------------------------------------------------------------===//
8753f127fSDimitry Andric 
9753f127fSDimitry Andric #ifndef _LIBCPP___ALGORITHM_RANGES_PARTITION_POINT_H
10753f127fSDimitry Andric #define _LIBCPP___ALGORITHM_RANGES_PARTITION_POINT_H
11753f127fSDimitry Andric 
12fcaf7f86SDimitry Andric #include <__algorithm/half_positive.h>
13753f127fSDimitry Andric #include <__config>
14753f127fSDimitry Andric #include <__functional/identity.h>
15753f127fSDimitry Andric #include <__functional/invoke.h>
16753f127fSDimitry Andric #include <__iterator/concepts.h>
17fcaf7f86SDimitry Andric #include <__iterator/distance.h>
18753f127fSDimitry Andric #include <__iterator/iterator_traits.h>
19fcaf7f86SDimitry Andric #include <__iterator/next.h>
20753f127fSDimitry Andric #include <__iterator/projected.h>
21753f127fSDimitry Andric #include <__ranges/access.h>
22753f127fSDimitry Andric #include <__ranges/concepts.h>
23753f127fSDimitry Andric #include <__ranges/dangling.h>
24753f127fSDimitry Andric #include <__utility/move.h>
25753f127fSDimitry Andric 
26753f127fSDimitry Andric #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
27753f127fSDimitry Andric #  pragma GCC system_header
28753f127fSDimitry Andric #endif
29753f127fSDimitry Andric 
30*b3edf446SDimitry Andric _LIBCPP_PUSH_MACROS
31*b3edf446SDimitry Andric #include <__undef_macros>
32*b3edf446SDimitry Andric 
3306c3fb27SDimitry Andric #if _LIBCPP_STD_VER >= 20
34753f127fSDimitry Andric 
35753f127fSDimitry Andric _LIBCPP_BEGIN_NAMESPACE_STD
36753f127fSDimitry Andric 
37753f127fSDimitry Andric namespace ranges {
38753f127fSDimitry Andric namespace __partition_point {
39753f127fSDimitry Andric 
40753f127fSDimitry Andric struct __fn {
41fcaf7f86SDimitry Andric   // TODO(ranges): delegate to the classic algorithm.
42fcaf7f86SDimitry Andric   template <class _Iter, class _Sent, class _Proj, class _Pred>
4306c3fb27SDimitry Andric   _LIBCPP_HIDE_FROM_ABI constexpr static _Iter
__partition_point_fn_impl__fn4406c3fb27SDimitry Andric   __partition_point_fn_impl(_Iter&& __first, _Sent&& __last, _Pred& __pred, _Proj& __proj) {
45fcaf7f86SDimitry Andric     auto __len = ranges::distance(__first, __last);
46fcaf7f86SDimitry Andric 
47fcaf7f86SDimitry Andric     while (__len != 0) {
48fcaf7f86SDimitry Andric       auto __half_len = std::__half_positive(__len);
49fcaf7f86SDimitry Andric       auto __mid      = ranges::next(__first, __half_len);
50fcaf7f86SDimitry Andric 
51fcaf7f86SDimitry Andric       if (std::invoke(__pred, std::invoke(__proj, *__mid))) {
52fcaf7f86SDimitry Andric         __first = ++__mid;
53fcaf7f86SDimitry Andric         __len -= __half_len + 1;
54fcaf7f86SDimitry Andric 
55fcaf7f86SDimitry Andric       } else {
56fcaf7f86SDimitry Andric         __len = __half_len;
57fcaf7f86SDimitry Andric       }
58fcaf7f86SDimitry Andric     }
59fcaf7f86SDimitry Andric 
60fcaf7f86SDimitry Andric     return __first;
61fcaf7f86SDimitry Andric   }
62fcaf7f86SDimitry Andric 
6306c3fb27SDimitry Andric   template <forward_iterator _Iter,
6406c3fb27SDimitry Andric             sentinel_for<_Iter> _Sent,
6506c3fb27SDimitry Andric             class _Proj = identity,
66753f127fSDimitry Andric             indirect_unary_predicate<projected<_Iter, _Proj>> _Pred>
operator__fn6706c3fb27SDimitry Andric   _LIBCPP_HIDE_FROM_ABI constexpr _Iter operator()(_Iter __first, _Sent __last, _Pred __pred, _Proj __proj = {}) const {
68fcaf7f86SDimitry Andric     return __partition_point_fn_impl(std::move(__first), std::move(__last), __pred, __proj);
69753f127fSDimitry Andric   }
70753f127fSDimitry Andric 
7106c3fb27SDimitry Andric   template <forward_range _Range,
7206c3fb27SDimitry Andric             class _Proj = identity,
73753f127fSDimitry Andric             indirect_unary_predicate<projected<iterator_t<_Range>, _Proj>> _Pred>
7406c3fb27SDimitry Andric   _LIBCPP_HIDE_FROM_ABI constexpr borrowed_iterator_t<_Range>
operator__fn7506c3fb27SDimitry Andric   operator()(_Range&& __range, _Pred __pred, _Proj __proj = {}) const {
76fcaf7f86SDimitry Andric     return __partition_point_fn_impl(ranges::begin(__range), ranges::end(__range), __pred, __proj);
77753f127fSDimitry Andric   }
78753f127fSDimitry Andric };
79753f127fSDimitry Andric 
80753f127fSDimitry Andric } // namespace __partition_point
81753f127fSDimitry Andric 
82753f127fSDimitry Andric inline namespace __cpo {
83753f127fSDimitry Andric inline constexpr auto partition_point = __partition_point::__fn{};
84753f127fSDimitry Andric } // namespace __cpo
85753f127fSDimitry Andric } // namespace ranges
86753f127fSDimitry Andric 
87753f127fSDimitry Andric _LIBCPP_END_NAMESPACE_STD
88753f127fSDimitry Andric 
8906c3fb27SDimitry Andric #endif // _LIBCPP_STD_VER >= 20
90753f127fSDimitry Andric 
91*b3edf446SDimitry Andric _LIBCPP_POP_MACROS
92*b3edf446SDimitry Andric 
93753f127fSDimitry Andric #endif // _LIBCPP___ALGORITHM_RANGES_PARTITION_POINT_H
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