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_NTH_ELEMENT_H
10 #define _LIBCPP___ALGORITHM_RANGES_NTH_ELEMENT_H
11 
12 #include <__algorithm/iterator_operations.h>
13 #include <__algorithm/make_projected.h>
14 #include <__algorithm/nth_element.h>
15 #include <__config>
16 #include <__functional/identity.h>
17 #include <__functional/invoke.h>
18 #include <__functional/ranges_operations.h>
19 #include <__iterator/concepts.h>
20 #include <__iterator/iterator_traits.h>
21 #include <__iterator/next.h>
22 #include <__iterator/projected.h>
23 #include <__iterator/sortable.h>
24 #include <__ranges/access.h>
25 #include <__ranges/concepts.h>
26 #include <__ranges/dangling.h>
27 #include <__utility/forward.h>
28 #include <__utility/move.h>
29 
30 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
31 #  pragma GCC system_header
32 #endif
33 
34 _LIBCPP_PUSH_MACROS
35 #include <__undef_macros>
36 
37 #if _LIBCPP_STD_VER >= 20
38 
39 _LIBCPP_BEGIN_NAMESPACE_STD
40 
41 namespace ranges {
42 namespace __nth_element {
43 
44 struct __fn {
45   template <class _Iter, class _Sent, class _Comp, class _Proj>
46   _LIBCPP_HIDE_FROM_ABI constexpr static _Iter
__nth_element_fn_impl__fn47   __nth_element_fn_impl(_Iter __first, _Iter __nth, _Sent __last, _Comp& __comp, _Proj& __proj) {
48     auto __last_iter = ranges::next(__first, __last);
49 
50     auto&& __projected_comp = std::__make_projected(__comp, __proj);
51     std::__nth_element_impl<_RangeAlgPolicy>(std::move(__first), std::move(__nth), __last_iter, __projected_comp);
52 
53     return __last_iter;
54   }
55 
56   template <random_access_iterator _Iter, sentinel_for<_Iter> _Sent, class _Comp = ranges::less, class _Proj = identity>
57     requires sortable<_Iter, _Comp, _Proj>
58   _LIBCPP_HIDE_FROM_ABI constexpr _Iter
operator__fn59   operator()(_Iter __first, _Iter __nth, _Sent __last, _Comp __comp = {}, _Proj __proj = {}) const {
60     return __nth_element_fn_impl(std::move(__first), std::move(__nth), std::move(__last), __comp, __proj);
61   }
62 
63   template <random_access_range _Range, class _Comp = ranges::less, class _Proj = identity>
64     requires sortable<iterator_t<_Range>, _Comp, _Proj>
65   _LIBCPP_HIDE_FROM_ABI constexpr borrowed_iterator_t<_Range>
operator__fn66   operator()(_Range&& __r, iterator_t<_Range> __nth, _Comp __comp = {}, _Proj __proj = {}) const {
67     return __nth_element_fn_impl(ranges::begin(__r), std::move(__nth), ranges::end(__r), __comp, __proj);
68   }
69 };
70 
71 } // namespace __nth_element
72 
73 inline namespace __cpo {
74 inline constexpr auto nth_element = __nth_element::__fn{};
75 } // namespace __cpo
76 } // namespace ranges
77 
78 _LIBCPP_END_NAMESPACE_STD
79 
80 #endif // _LIBCPP_STD_VER >= 20
81 
82 _LIBCPP_POP_MACROS
83 
84 #endif // _LIBCPP___ALGORITHM_RANGES_NTH_ELEMENT_H
85