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
47namespace ranges {
48
49template <view _View, class _Pred>
50 requires input_range<_View> && is_object_v<_Pred> && indirect_unary_predicate<const _Pred, iterator_t<_View>>
51class _LIBCPP_ABI_LLVM18_NO_UNIQUE_ADDRESS drop_while_view : public view_interface<drop_while_view<_View, _Pred>> {
52public:
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
88private:
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 _LIBCPP_NODEBUG = _If<_UseCache, __non_propagating_cache<iterator_t<_View>>, __empty_cache>;
94 _LIBCPP_NO_UNIQUE_ADDRESS _Cache __cached_begin_ = _Cache();
95};
96
97template <class _View, class _Pred>
98inline constexpr bool enable_borrowed_range<drop_while_view<_View, _Pred>> = enable_borrowed_range<_View>;
99
100template <class _Range, class _Pred>
101drop_while_view(_Range&&, _Pred) -> drop_while_view<views::all_t<_Range>, _Pred>;
102
103namespace views {
104namespace __drop_while {
105
106struct __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 __pipeable(std::__bind_back(*this, std::forward<_Pred>(__pred)));
119 }
120};
121
122} // namespace __drop_while
123
124inline namespace __cpo {
125inline 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