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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_TO_H
11#define _LIBCPP___RANGES_TO_H
12
13#include <__concepts/constructible.h>
14#include <__concepts/convertible_to.h>
15#include <__concepts/derived_from.h>
16#include <__concepts/same_as.h>
17#include <__config>
18#include <__cstddef/ptrdiff_t.h>
19#include <__functional/bind_back.h>
20#include <__iterator/iterator_traits.h>
21#include <__ranges/access.h>
22#include <__ranges/concepts.h>
23#include <__ranges/from_range.h>
24#include <__ranges/range_adaptor.h>
25#include <__ranges/ref_view.h>
26#include <__ranges/size.h>
27#include <__ranges/transform_view.h>
28#include <__type_traits/add_pointer.h>
29#include <__type_traits/is_class.h>
30#include <__type_traits/is_const.h>
31#include <__type_traits/is_union.h>
32#include <__type_traits/is_volatile.h>
33#include <__type_traits/type_identity.h>
34#include <__utility/declval.h>
35#include <__utility/forward.h>
36
37#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
38# pragma GCC system_header
39#endif
40
41_LIBCPP_BEGIN_NAMESPACE_STD
42
43#if _LIBCPP_STD_VER >= 23
44
45namespace ranges {
46
47template <class _Container>
48constexpr bool __reservable_container =
49 sized_range<_Container> && requires(_Container& __c, range_size_t<_Container> __n) {
50 __c.reserve(__n);
51 { __c.capacity() } -> same_as<decltype(__n)>;
52 { __c.max_size() } -> same_as<decltype(__n)>;
53 };
54
55template <class _Container, class _Ref>
56constexpr bool __container_appendable = requires(_Container& __c, _Ref&& __ref) {
57 requires(
58 requires { __c.emplace_back(std::forward<_Ref>(__ref)); } ||
59 requires { __c.push_back(std::forward<_Ref>(__ref)); } ||
60 requires { __c.emplace(__c.end(), std::forward<_Ref>(__ref)); } ||
61 requires { __c.insert(__c.end(), std::forward<_Ref>(__ref)); });
62};
63
64// Note: making this a concept allows short-circuiting the second condition.
65template <class _Container, class _Range>
66concept __try_non_recursive_conversion =
67 !input_range<_Container> || convertible_to<range_reference_t<_Range>, range_value_t<_Container>>;
68
69template <class _Container, class _Range, class... _Args>
70concept __constructible_from_iter_pair =
71 common_range<_Range> && requires { typename iterator_traits<iterator_t<_Range>>::iterator_category; } &&
72 derived_from<typename iterator_traits<iterator_t<_Range>>::iterator_category, input_iterator_tag> &&
73 constructible_from<_Container, iterator_t<_Range>, sentinel_t<_Range>, _Args...>;
74
75template <class>
76concept __always_false = false;
77
78// `ranges::to` base template -- the `_Container` type is a simple type template parameter.
79template <class _Container, input_range _Range, class... _Args>
80 requires(!view<_Container>)
81[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Container to(_Range&& __range, _Args&&... __args) {
82 // Mandates: C is a cv-unqualified class type.
83 static_assert(!is_const_v<_Container>, "The target container cannot be const-qualified, please remove the const");
84 static_assert(
85 !is_volatile_v<_Container>, "The target container cannot be volatile-qualified, please remove the volatile");
86 static_assert(is_class_v<_Container> || is_union_v<_Container>, "The target must be a class type or union type");
87 // First see if the non-recursive case applies -- the conversion target is either:
88 // - a range with a convertible value type;
89 // - a non-range type which might support being created from the input argument(s) (e.g. an `optional`).
90 if constexpr (__try_non_recursive_conversion<_Container, _Range>) {
91 // Case 1 -- construct directly from the given range.
92 if constexpr (constructible_from<_Container, _Range, _Args...>) {
93 return _Container(std::forward<_Range>(__range), std::forward<_Args>(__args)...);
94 }
95
96 // Case 2 -- construct using the `from_range_t` tagged constructor.
97 else if constexpr (constructible_from<_Container, from_range_t, _Range, _Args...>) {
98 return _Container(from_range, std::forward<_Range>(__range), std::forward<_Args>(__args)...);
99 }
100
101 // Case 3 -- construct from a begin-end iterator pair.
102 else if constexpr (__constructible_from_iter_pair<_Container, _Range, _Args...>) {
103 return _Container(ranges::begin(__range), ranges::end(__range), std::forward<_Args>(__args)...);
104 }
105
106 // Case 4 -- default-construct (or construct from the extra arguments) and insert, reserving the size if possible.
107 else if constexpr (constructible_from<_Container, _Args...> &&
108 __container_appendable<_Container, range_reference_t<_Range>>) {
109 _Container __result(std::forward<_Args>(__args)...);
110 if constexpr (sized_range<_Range> && __reservable_container<_Container>) {
111 __result.reserve(static_cast<range_size_t<_Container>>(ranges::size(__range)));
112 }
113
114 for (auto&& __ref : __range) {
115 using _Ref = decltype(__ref);
116 if constexpr (requires { __result.emplace_back(std::declval<_Ref>()); }) {
117 __result.emplace_back(std::forward<_Ref>(__ref));
118 } else if constexpr (requires { __result.push_back(std::declval<_Ref>()); }) {
119 __result.push_back(std::forward<_Ref>(__ref));
120 } else if constexpr (requires { __result.emplace(__result.end(), std::declval<_Ref>()); }) {
121 __result.emplace(__result.end(), std::forward<_Ref>(__ref));
122 } else {
123 static_assert(requires { __result.insert(__result.end(), std::declval<_Ref>()); });
124 __result.insert(__result.end(), std::forward<_Ref>(__ref));
125 }
126 }
127 return __result;
128
129 } else {
130 static_assert(__always_false<_Container>, "ranges::to: unable to convert to the given container type.");
131 }
132
133 // Try the recursive case.
134 } else if constexpr (input_range<range_reference_t<_Range>>) {
135 return ranges::to<_Container>(
136 ref_view(__range) | views::transform([](auto&& __elem) {
137 return ranges::to<range_value_t<_Container>>(std::forward<decltype(__elem)>(__elem));
138 }),
139 std::forward<_Args>(__args)...);
140
141 } else {
142 static_assert(__always_false<_Container>, "ranges::to: unable to convert to the given container type.");
143 }
144}
145
146template <class _Range>
147struct __minimal_input_iterator {
148 using iterator_category = input_iterator_tag;
149 using value_type = range_value_t<_Range>;
150 using difference_type = ptrdiff_t;
151 using pointer = add_pointer_t<range_reference_t<_Range>>;
152 using reference = range_reference_t<_Range>;
153
154 reference operator*() const;
155 pointer operator->() const;
156 __minimal_input_iterator& operator++();
157 __minimal_input_iterator operator++(int);
158 bool operator==(const __minimal_input_iterator&) const;
159};
160
161// Deduces the full type of the container from the given template template parameter.
162template <template <class...> class _Container, input_range _Range, class... _Args>
163struct _Deducer {
164 _LIBCPP_HIDE_FROM_ABI static constexpr auto __deduce_func() {
165 using _InputIter = __minimal_input_iterator<_Range>;
166
167 // Case 1 -- can construct directly from the given range.
168 if constexpr (requires { _Container(std::declval<_Range>(), std::declval<_Args>()...); }) {
169 using _Result = decltype( //
170 _Container(std::declval<_Range>(), std::declval<_Args>()...));
171 return type_identity<_Result>{};
172
173 // Case 2 -- can construct from the given range using the `from_range_t` tagged constructor.
174 } else if constexpr ( //
175 requires { _Container(from_range, std::declval<_Range>(), std::declval<_Args>()...); }) {
176 using _Result = //
177 decltype(_Container(from_range, std::declval<_Range>(), std::declval<_Args>()...));
178 return type_identity<_Result>{};
179
180 // Case 3 -- can construct from a begin-end iterator pair.
181 } else if constexpr ( //
182 requires { _Container(std::declval<_InputIter>(), std::declval<_InputIter>(), std::declval<_Args>()...); }) {
183 using _Result =
184 decltype(_Container(std::declval<_InputIter>(), std::declval<_InputIter>(), std::declval<_Args>()...));
185 return type_identity<_Result>{};
186
187 } else {
188 static_assert(__always_false<_Range>,
189 "ranges::to: unable to deduce the container type from the template template argument.");
190 }
191 }
192
193 using type = typename decltype(__deduce_func())::type;
194};
195
196// `ranges::to` specialization -- `_Container` is a template template parameter requiring deduction to figure out the
197// container element type.
198template <template <class...> class _Container, input_range _Range, class... _Args>
199[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto to(_Range&& __range, _Args&&... __args) {
200 using _DeduceExpr = typename _Deducer<_Container, _Range, _Args...>::type;
201 return ranges::to<_DeduceExpr>(std::forward<_Range>(__range), std::forward<_Args>(__args)...);
202}
203
204// Range adaptor closure object 1 -- wrapping the `ranges::to` version where `_Container` is a simple type template
205// parameter.
206template <class _Container, class... _Args>
207 requires(!view<_Container>)
208[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto to(_Args&&... __args) {
209 // Mandates: C is a cv-unqualified class type.
210 static_assert(!is_const_v<_Container>, "The target container cannot be const-qualified, please remove the const");
211 static_assert(
212 !is_volatile_v<_Container>, "The target container cannot be volatile-qualified, please remove the volatile");
213 static_assert(is_class_v<_Container> || is_union_v<_Container>, "The target must be a class type or union type");
214 auto __to_func = []<input_range _Range, class... _Tail>(_Range&& __range, _Tail&&... __tail) static
215 requires requires { //
216 /**/ ranges::to<_Container>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...);
217 }
218 { return ranges::to<_Container>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...); };
219
220 return __pipeable(std::__bind_back(__to_func, std::forward<_Args>(__args)...));
221}
222
223// Range adaptor closure object 2 -- wrapping the `ranges::to` version where `_Container` is a template template
224// parameter.
225template <template <class...> class _Container, class... _Args>
226[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto to(_Args&&... __args) {
227 // clang-format off
228 auto __to_func = []<input_range _Range, class... _Tail,
229 class _DeducedExpr = typename _Deducer<_Container, _Range, _Tail...>::type>
230 (_Range&& __range, _Tail&& ... __tail) static
231 requires requires { //
232 /**/ ranges::to<_DeducedExpr>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...);
233 }
234 {
235 return ranges::to<_DeducedExpr>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...);
236 };
237 // clang-format on
238
239 return __pipeable(std::__bind_back(__to_func, std::forward<_Args>(__args)...));
240}
241
242} // namespace ranges
243
244#endif // _LIBCPP_STD_VER >= 23
245
246_LIBCPP_END_NAMESPACE_STD
247
248#endif // _LIBCPP___RANGES_TO_H