libcxx/include/__algorithm/ranges_nth_element.h

   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 struct __nth_element {
  43   template <class _Iter, class _Sent, class _Comp, class _Proj>
  44   _LIBCPP_HIDE_FROM_ABI constexpr static _Iter
  45   __nth_element_fn_impl(_Iter __first, _Iter __nth, _Sent __last, _Comp& __comp, _Proj& __proj) {
  46     auto __last_iter = ranges::next(__first, __last);
  47
  48     auto&& __projected_comp = std::__make_projected(__comp, __proj);
  49     std::__nth_element_impl<_RangeAlgPolicy>(std::move(__first), std::move(__nth), __last_iter, __projected_comp);
  50
  51     return __last_iter;
  52   }
  53
  54   template <random_access_iterator _Iter, sentinel_for<_Iter> _Sent, class _Comp = ranges::less, class _Proj = identity>
  55     requires sortable<_Iter, _Comp, _Proj>
  56   _LIBCPP_HIDE_FROM_ABI constexpr _Iter
  57   operator()(_Iter __first, _Iter __nth, _Sent __last, _Comp __comp = {}, _Proj __proj = {}) const {
  58     return __nth_element_fn_impl(std::move(__first), std::move(__nth), std::move(__last), __comp, __proj);
  59   }
  60
  61   template <random_access_range _Range, class _Comp = ranges::less, class _Proj = identity>
  62     requires sortable<iterator_t<_Range>, _Comp, _Proj>
  63   _LIBCPP_HIDE_FROM_ABI constexpr borrowed_iterator_t<_Range>
  64   operator()(_Range&& __r, iterator_t<_Range> __nth, _Comp __comp = {}, _Proj __proj = {}) const {
  65     return __nth_element_fn_impl(ranges::begin(__r), std::move(__nth), ranges::end(__r), __comp, __proj);
  66   }
  67 };
  68
  69 inline namespace __cpo {
  70 inline constexpr auto nth_element = __nth_element{};
  71 } // namespace __cpo
  72 } // namespace ranges
  73
  74 _LIBCPP_END_NAMESPACE_STD
  75
  76 #endif // _LIBCPP_STD_VER >= 20
  77
  78 _LIBCPP_POP_MACROS
  79
  80 #endif // _LIBCPP___ALGORITHM_RANGES_NTH_ELEMENT_H