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_DROP_WHILE_VIEW_H 11 #define _LIBCPP___RANGES_DROP_WHILE_VIEW_H 12 13 #include <__algorithm/ranges_find_if_not.h> 14 #include <__assert> 15 #include <__concepts/constructible.h> 16 #include <__config> 17 #include <__functional/bind_back.h> 18 #include <__functional/reference_wrapper.h> 19 #include <__iterator/concepts.h> 20 #include <__ranges/access.h> 21 #include <__ranges/all.h> 22 #include <__ranges/concepts.h> 23 #include <__ranges/enable_borrowed_range.h> 24 #include <__ranges/movable_box.h> 25 #include <__ranges/non_propagating_cache.h> 26 #include <__ranges/range_adaptor.h> 27 #include <__ranges/view_interface.h> 28 #include <__type_traits/conditional.h> 29 #include <__type_traits/decay.h> 30 #include <__type_traits/is_nothrow_constructible.h> 31 #include <__type_traits/is_object.h> 32 #include <__utility/forward.h> 33 #include <__utility/in_place.h> 34 #include <__utility/move.h> 35 36 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 37 # pragma GCC system_header 38 #endif 39 40 _LIBCPP_BEGIN_NAMESPACE_STD 41 42 #if _LIBCPP_STD_VER >= 20 43 44 namespace ranges { 45 46 template <view _View, class _Pred> 47 requires input_range<_View> && is_object_v<_Pred> && indirect_unary_predicate<const _Pred, iterator_t<_View>> 48 class _LIBCPP_ABI_2023_OVERLAPPING_SUBOBJECT_FIX_TAG drop_while_view 49 : public view_interface<drop_while_view<_View, _Pred>> { 50 public: 51 _LIBCPP_HIDE_FROM_ABI drop_while_view() 52 requires default_initializable<_View> && default_initializable<_Pred> 53 = default; 54 55 _LIBCPP_HIDE_FROM_ABI constexpr _LIBCPP_EXPLICIT_SINCE_CXX23 drop_while_view(_View __base, _Pred __pred) 56 : __base_(std::move(__base)), __pred_(std::in_place, std::move(__pred)) {} 57 58 _LIBCPP_HIDE_FROM_ABI constexpr _View base() const& 59 requires copy_constructible<_View> 60 { 61 return __base_; 62 } 63 64 _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); } 65 66 _LIBCPP_HIDE_FROM_ABI constexpr const _Pred& pred() const { return *__pred_; } 67 68 _LIBCPP_HIDE_FROM_ABI constexpr auto begin() { 69 // Note: this duplicates a check in `optional` but provides a better error message. 70 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 71 __pred_.__has_value(), 72 "drop_while_view needs to have a non-empty predicate before calling begin() -- did a previous " 73 "assignment to this drop_while_view fail?"); 74 if constexpr (_UseCache) { 75 if (!__cached_begin_.__has_value()) { 76 __cached_begin_.__emplace(ranges::find_if_not(__base_, std::cref(*__pred_))); 77 } 78 return *__cached_begin_; 79 } else { 80 return ranges::find_if_not(__base_, std::cref(*__pred_)); 81 } 82 } 83 84 _LIBCPP_HIDE_FROM_ABI constexpr auto end() { return ranges::end(__base_); } 85 86 private: 87 _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View(); 88 _LIBCPP_NO_UNIQUE_ADDRESS __movable_box<_Pred> __pred_; 89 90 static constexpr bool _UseCache = forward_range<_View>; 91 using _Cache = _If<_UseCache, __non_propagating_cache<iterator_t<_View>>, __empty_cache>; 92 _LIBCPP_NO_UNIQUE_ADDRESS _Cache __cached_begin_ = _Cache(); 93 }; 94 95 template <class _View, class _Pred> 96 inline constexpr bool enable_borrowed_range<drop_while_view<_View, _Pred>> = enable_borrowed_range<_View>; 97 98 template <class _Range, class _Pred> 99 drop_while_view(_Range&&, _Pred) -> drop_while_view<views::all_t<_Range>, _Pred>; 100 101 namespace views { 102 namespace __drop_while { 103 104 struct __fn { 105 template <class _Range, class _Pred> 106 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Pred&& __pred) const 107 noexcept(noexcept(/**/ drop_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred)))) 108 -> decltype(/*--*/ drop_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))) { 109 return /*-------------*/ drop_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred)); 110 } 111 112 template <class _Pred> 113 requires constructible_from<decay_t<_Pred>, _Pred> 114 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Pred&& __pred) const 115 noexcept(is_nothrow_constructible_v<decay_t<_Pred>, _Pred>) { 116 return __range_adaptor_closure_t(std::__bind_back(*this, std::forward<_Pred>(__pred))); 117 } 118 }; 119 120 } // namespace __drop_while 121 122 inline namespace __cpo { 123 inline constexpr auto drop_while = __drop_while::__fn{}; 124 } // namespace __cpo 125 } // namespace views 126 } // namespace ranges 127 128 #endif // _LIBCPP_STD_VER >= 20 129 130 _LIBCPP_END_NAMESPACE_STD 131 132 #endif // _LIBCPP___RANGES_DROP_WHILE_VIEW_H 133