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 #if _LIBCPP_STD_VER >= 20 31 32 _LIBCPP_BEGIN_NAMESPACE_STD 33 34 namespace ranges { 35 namespace __partition_point { 36 37 struct __fn { 38 // TODO(ranges): delegate to the classic algorithm. 39 template <class _Iter, class _Sent, class _Proj, class _Pred> 40 _LIBCPP_HIDE_FROM_ABI constexpr static _Iter 41 __partition_point_fn_impl(_Iter&& __first, _Sent&& __last, _Pred& __pred, _Proj& __proj) { 42 auto __len = ranges::distance(__first, __last); 43 44 while (__len != 0) { 45 auto __half_len = std::__half_positive(__len); 46 auto __mid = ranges::next(__first, __half_len); 47 48 if (std::invoke(__pred, std::invoke(__proj, *__mid))) { 49 __first = ++__mid; 50 __len -= __half_len + 1; 51 52 } else { 53 __len = __half_len; 54 } 55 } 56 57 return __first; 58 } 59 60 template <forward_iterator _Iter, 61 sentinel_for<_Iter> _Sent, 62 class _Proj = identity, 63 indirect_unary_predicate<projected<_Iter, _Proj>> _Pred> 64 _LIBCPP_HIDE_FROM_ABI constexpr _Iter operator()(_Iter __first, _Sent __last, _Pred __pred, _Proj __proj = {}) const { 65 return __partition_point_fn_impl(std::move(__first), std::move(__last), __pred, __proj); 66 } 67 68 template <forward_range _Range, 69 class _Proj = identity, 70 indirect_unary_predicate<projected<iterator_t<_Range>, _Proj>> _Pred> 71 _LIBCPP_HIDE_FROM_ABI constexpr borrowed_iterator_t<_Range> 72 operator()(_Range&& __range, _Pred __pred, _Proj __proj = {}) const { 73 return __partition_point_fn_impl(ranges::begin(__range), ranges::end(__range), __pred, __proj); 74 } 75 }; 76 77 } // namespace __partition_point 78 79 inline namespace __cpo { 80 inline constexpr auto partition_point = __partition_point::__fn{}; 81 } // namespace __cpo 82 } // namespace ranges 83 84 _LIBCPP_END_NAMESPACE_STD 85 86 #endif // _LIBCPP_STD_VER >= 20 87 88 #endif // _LIBCPP___ALGORITHM_RANGES_PARTITION_POINT_H 89