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/copyable_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
42namespace 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.
52template <class _View, class _Pred>
53concept __take_while_const_is_range =
54    range<const _View> && indirect_unary_predicate<const _Pred, iterator_t<const _View>>;
55
56template <view _View, class _Pred>
57  requires input_range<_View> && is_object_v<_Pred> && indirect_unary_predicate<const _Pred, iterator_t<_View>>
58class 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 __copyable_box<_Pred> __pred_;
64
65public:
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 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
108template <class _Range, class _Pred>
109take_while_view(_Range&&, _Pred) -> take_while_view<views::all_t<_Range>, _Pred>;
110
111template <view _View, class _Pred>
112  requires input_range<_View> && is_object_v<_Pred> && indirect_unary_predicate<const _Pred, iterator_t<_View>>
113template <bool _Const>
114class 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
122public:
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
146namespace views {
147namespace __take_while {
148
149struct __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
167inline namespace __cpo {
168inline 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