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_PUSH_MACROS
41 #include <__undef_macros>
42 
43 _LIBCPP_BEGIN_NAMESPACE_STD
44 
45 #if _LIBCPP_STD_VER >= 20
46 
47 namespace ranges {
48 
49 template <view _View, class _Pred>
50   requires input_range<_View> && is_object_v<_Pred> && indirect_unary_predicate<const _Pred, iterator_t<_View>>
51 class _LIBCPP_ABI_LLVM18_NO_UNIQUE_ADDRESS drop_while_view : public view_interface<drop_while_view<_View, _Pred>> {
52 public:
53   _LIBCPP_HIDE_FROM_ABI drop_while_view()
54     requires default_initializable<_View> && default_initializable<_Pred>
55   = default;
56 
57   _LIBCPP_HIDE_FROM_ABI constexpr _LIBCPP_EXPLICIT_SINCE_CXX23 drop_while_view(_View __base, _Pred __pred)
58       : __base_(std::move(__base)), __pred_(std::in_place, std::move(__pred)) {}
59 
60   _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
61     requires copy_constructible<_View>
62   {
63     return __base_;
64   }
65 
66   _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
67 
68   _LIBCPP_HIDE_FROM_ABI constexpr const _Pred& pred() const { return *__pred_; }
69 
70   _LIBCPP_HIDE_FROM_ABI constexpr auto begin() {
71     // Note: this duplicates a check in `optional` but provides a better error message.
72     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
73         __pred_.__has_value(),
74         "drop_while_view needs to have a non-empty predicate before calling begin() -- did a previous "
75         "assignment to this drop_while_view fail?");
76     if constexpr (_UseCache) {
77       if (!__cached_begin_.__has_value()) {
78         __cached_begin_.__emplace(ranges::find_if_not(__base_, std::cref(*__pred_)));
79       }
80       return *__cached_begin_;
81     } else {
82       return ranges::find_if_not(__base_, std::cref(*__pred_));
83     }
84   }
85 
86   _LIBCPP_HIDE_FROM_ABI constexpr auto end() { return ranges::end(__base_); }
87 
88 private:
89   _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
90   _LIBCPP_NO_UNIQUE_ADDRESS __movable_box<_Pred> __pred_;
91 
92   static constexpr bool _UseCache = forward_range<_View>;
93   using _Cache                    = _If<_UseCache, __non_propagating_cache<iterator_t<_View>>, __empty_cache>;
94   _LIBCPP_NO_UNIQUE_ADDRESS _Cache __cached_begin_ = _Cache();
95 };
96 
97 template <class _View, class _Pred>
98 inline constexpr bool enable_borrowed_range<drop_while_view<_View, _Pred>> = enable_borrowed_range<_View>;
99 
100 template <class _Range, class _Pred>
101 drop_while_view(_Range&&, _Pred) -> drop_while_view<views::all_t<_Range>, _Pred>;
102 
103 namespace views {
104 namespace __drop_while {
105 
106 struct __fn {
107   template <class _Range, class _Pred>
108   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Pred&& __pred) const
109       noexcept(noexcept(/**/ drop_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))))
110           -> decltype(/*--*/ drop_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))) {
111     return /*-------------*/ drop_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred));
112   }
113 
114   template <class _Pred>
115     requires constructible_from<decay_t<_Pred>, _Pred>
116   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Pred&& __pred) const
117       noexcept(is_nothrow_constructible_v<decay_t<_Pred>, _Pred>) {
118     return __range_adaptor_closure_t(std::__bind_back(*this, std::forward<_Pred>(__pred)));
119   }
120 };
121 
122 } // namespace __drop_while
123 
124 inline namespace __cpo {
125 inline constexpr auto drop_while = __drop_while::__fn{};
126 } // namespace __cpo
127 } // namespace views
128 } // namespace ranges
129 
130 #endif // _LIBCPP_STD_VER >= 20
131 
132 _LIBCPP_END_NAMESPACE_STD
133 
134 _LIBCPP_POP_MACROS
135 
136 #endif // _LIBCPP___RANGES_DROP_WHILE_VIEW_H
137