1 // -*- C++ -*- 2 //===----------------------------------------------------------------------===// 3 // 4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 5 // See https://llvm.org/LICENSE.txt for license information. 6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 7 // 8 //===----------------------------------------------------------------------===// 9 10 #ifndef _LIBCPP___RANGES_TAKE_WHILE_VIEW_H 11 #define _LIBCPP___RANGES_TAKE_WHILE_VIEW_H 12 13 #include <__concepts/constructible.h> 14 #include <__concepts/convertible_to.h> 15 #include <__config> 16 #include <__functional/bind_back.h> 17 #include <__functional/invoke.h> 18 #include <__iterator/concepts.h> 19 #include <__memory/addressof.h> 20 #include <__ranges/access.h> 21 #include <__ranges/all.h> 22 #include <__ranges/concepts.h> 23 #include <__ranges/movable_box.h> 24 #include <__ranges/range_adaptor.h> 25 #include <__ranges/view_interface.h> 26 #include <__type_traits/decay.h> 27 #include <__type_traits/is_nothrow_constructible.h> 28 #include <__type_traits/is_object.h> 29 #include <__type_traits/maybe_const.h> 30 #include <__utility/forward.h> 31 #include <__utility/in_place.h> 32 #include <__utility/move.h> 33 34 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 35 # pragma GCC system_header 36 #endif 37 38 _LIBCPP_BEGIN_NAMESPACE_STD 39 40 #if _LIBCPP_STD_VER >= 20 41 42 namespace ranges { 43 44 // The spec uses the unnamed requirement inside the `begin` and `end` member functions: 45 // constexpr auto begin() const 46 // requires range<const V> && indirect_unary_predicate<const Pred, iterator_t<const V>> 47 // However, due to a clang-14 and clang-15 bug, the above produces a hard error when `const V` is not a range. 48 // The workaround is to create a named concept and use the concept instead. 49 // As of take_while_view is implemented, the clang-trunk has already fixed the bug. 50 // It is OK to remove the workaround once our CI no longer uses clang-14, clang-15 based compilers, 51 // because we don't actually expect a lot of vendors to ship a new libc++ with an old clang. 52 template <class _View, class _Pred> 53 concept __take_while_const_is_range = 54 range<const _View> && indirect_unary_predicate<const _Pred, iterator_t<const _View>>; 55 56 template <view _View, class _Pred> 57 requires input_range<_View> && is_object_v<_Pred> && indirect_unary_predicate<const _Pred, iterator_t<_View>> 58 class take_while_view : public view_interface<take_while_view<_View, _Pred>> { 59 template <bool> 60 class __sentinel; 61 62 _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View(); 63 _LIBCPP_NO_UNIQUE_ADDRESS __movable_box<_Pred> __pred_; 64 65 public: 66 _LIBCPP_HIDE_FROM_ABI take_while_view() 67 requires default_initializable<_View> && default_initializable<_Pred> 68 = default; 69 70 _LIBCPP_HIDE_FROM_ABI constexpr _LIBCPP_EXPLICIT_SINCE_CXX23 take_while_view(_View __base, _Pred __pred) 71 : __base_(std::move(__base)), __pred_(std::in_place, std::move(__pred)) {} 72 73 _LIBCPP_HIDE_FROM_ABI constexpr _View base() const& 74 requires copy_constructible<_View> 75 { 76 return __base_; 77 } 78 79 _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); } 80 81 _LIBCPP_HIDE_FROM_ABI constexpr const _Pred& pred() const { return *__pred_; } 82 83 _LIBCPP_HIDE_FROM_ABI constexpr auto begin() 84 requires(!__simple_view<_View>) 85 { 86 return ranges::begin(__base_); 87 } 88 89 _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const 90 requires __take_while_const_is_range<_View, _Pred> 91 { 92 return ranges::begin(__base_); 93 } 94 95 _LIBCPP_HIDE_FROM_ABI constexpr auto end() 96 requires(!__simple_view<_View>) 97 { 98 return __sentinel</*_Const=*/false>(ranges::end(__base_), std::addressof(*__pred_)); 99 } 100 101 _LIBCPP_HIDE_FROM_ABI constexpr auto end() const 102 requires __take_while_const_is_range<_View, _Pred> 103 { 104 return __sentinel</*_Const=*/true>(ranges::end(__base_), std::addressof(*__pred_)); 105 } 106 }; 107 108 template <class _Range, class _Pred> 109 take_while_view(_Range&&, _Pred) -> take_while_view<views::all_t<_Range>, _Pred>; 110 111 template <view _View, class _Pred> 112 requires input_range<_View> && is_object_v<_Pred> && indirect_unary_predicate<const _Pred, iterator_t<_View>> 113 template <bool _Const> 114 class take_while_view<_View, _Pred>::__sentinel { 115 using _Base = __maybe_const<_Const, _View>; 116 117 sentinel_t<_Base> __end_ = sentinel_t<_Base>(); 118 const _Pred* __pred_ = nullptr; 119 120 friend class __sentinel<!_Const>; 121 122 public: 123 _LIBCPP_HIDE_FROM_ABI __sentinel() = default; 124 125 _LIBCPP_HIDE_FROM_ABI constexpr explicit __sentinel(sentinel_t<_Base> __end, const _Pred* __pred) 126 : __end_(std::move(__end)), __pred_(__pred) {} 127 128 _LIBCPP_HIDE_FROM_ABI constexpr __sentinel(__sentinel<!_Const> __s) 129 requires _Const && convertible_to<sentinel_t<_View>, sentinel_t<_Base>> 130 : __end_(std::move(__s.__end_)), __pred_(__s.__pred_) {} 131 132 _LIBCPP_HIDE_FROM_ABI constexpr sentinel_t<_Base> base() const { return __end_; } 133 134 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const iterator_t<_Base>& __x, const __sentinel& __y) { 135 return __x == __y.__end_ || !std::invoke(*__y.__pred_, *__x); 136 } 137 138 template <bool _OtherConst = !_Const> 139 requires sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>> 140 _LIBCPP_HIDE_FROM_ABI friend constexpr bool 141 operator==(const iterator_t<__maybe_const<_OtherConst, _View>>& __x, const __sentinel& __y) { 142 return __x == __y.__end_ || !std::invoke(*__y.__pred_, *__x); 143 } 144 }; 145 146 namespace views { 147 namespace __take_while { 148 149 struct __fn { 150 template <class _Range, class _Pred> 151 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Pred&& __pred) const 152 noexcept(noexcept(/**/ take_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred)))) 153 -> decltype(/*--*/ take_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))) { 154 return /*-------------*/ take_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred)); 155 } 156 157 template <class _Pred> 158 requires constructible_from<decay_t<_Pred>, _Pred> 159 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Pred&& __pred) const 160 noexcept(is_nothrow_constructible_v<decay_t<_Pred>, _Pred>) { 161 return __range_adaptor_closure_t(std::__bind_back(*this, std::forward<_Pred>(__pred))); 162 } 163 }; 164 165 } // namespace __take_while 166 167 inline namespace __cpo { 168 inline constexpr auto take_while = __take_while::__fn{}; 169 } // namespace __cpo 170 } // namespace views 171 } // namespace ranges 172 173 #endif // _LIBCPP_STD_VER >= 20 174 175 _LIBCPP_END_NAMESPACE_STD 176 177 #endif // _LIBCPP___RANGES_TAKE_WHILE_VIEW_H 178