libcxx/include/__algorithm/ranges_partition_point.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_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
  37 namespace ranges {
  38 struct __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
  78 inline namespace __cpo {
  79 inline 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