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_const.h>
30 #include <__type_traits/is_volatile.h>
31 #include <__type_traits/type_identity.h>
32 #include <__utility/declval.h>
33 #include <__utility/forward.h>
34
35 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
36 # pragma GCC system_header
37 #endif
38
39 _LIBCPP_BEGIN_NAMESPACE_STD
40
41 #if _LIBCPP_STD_VER >= 23
42
43 namespace ranges {
44
45 template <class _Container>
46 constexpr bool __reservable_container =
requires(_Container & __c,range_size_t<_Container> __n)47 sized_range<_Container> && requires(_Container& __c, range_size_t<_Container> __n) {
48 __c.reserve(__n);
49 { __c.capacity() } -> same_as<decltype(__n)>;
50 { __c.max_size() } -> same_as<decltype(__n)>;
51 };
52
53 template <class _Container, class _Ref>
requires(_Container & __c,_Ref && __ref)54 constexpr bool __container_appendable = requires(_Container& __c, _Ref&& __ref) {
55 requires(
56 requires { __c.emplace_back(std::forward<_Ref>(__ref)); } ||
57 requires { __c.push_back(std::forward<_Ref>(__ref)); } ||
58 requires { __c.emplace(__c.end(), std::forward<_Ref>(__ref)); } ||
59 requires { __c.insert(__c.end(), std::forward<_Ref>(__ref)); });
60 };
61
62 // Note: making this a concept allows short-circuiting the second condition.
63 template <class _Container, class _Range>
64 concept __try_non_recursive_conversion =
65 !input_range<_Container> || convertible_to<range_reference_t<_Range>, range_value_t<_Container>>;
66
67 template <class _Container, class _Range, class... _Args>
68 concept __constructible_from_iter_pair =
69 common_range<_Range> && requires { typename iterator_traits<iterator_t<_Range>>::iterator_category; } &&
70 derived_from<typename iterator_traits<iterator_t<_Range>>::iterator_category, input_iterator_tag> &&
71 constructible_from<_Container, iterator_t<_Range>, sentinel_t<_Range>, _Args...>;
72
73 template <class>
74 concept __always_false = false;
75
76 // `ranges::to` base template -- the `_Container` type is a simple type template parameter.
77 template <class _Container, input_range _Range, class... _Args>
78 requires(!view<_Container>)
to(_Range && __range,_Args &&...__args)79 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Container to(_Range&& __range, _Args&&... __args) {
80 // Mandates: C is a cv-unqualified class type.
81 static_assert(!is_const_v<_Container>, "The target container cannot be const-qualified, please remove the const");
82 static_assert(
83 !is_volatile_v<_Container>, "The target container cannot be volatile-qualified, please remove the volatile");
84
85 // First see if the non-recursive case applies -- the conversion target is either:
86 // - a range with a convertible value type;
87 // - a non-range type which might support being created from the input argument(s) (e.g. an `optional`).
88 if constexpr (__try_non_recursive_conversion<_Container, _Range>) {
89 // Case 1 -- construct directly from the given range.
90 if constexpr (constructible_from<_Container, _Range, _Args...>) {
91 return _Container(std::forward<_Range>(__range), std::forward<_Args>(__args)...);
92 }
93
94 // Case 2 -- construct using the `from_range_t` tagged constructor.
95 else if constexpr (constructible_from<_Container, from_range_t, _Range, _Args...>) {
96 return _Container(from_range, std::forward<_Range>(__range), std::forward<_Args>(__args)...);
97 }
98
99 // Case 3 -- construct from a begin-end iterator pair.
100 else if constexpr (__constructible_from_iter_pair<_Container, _Range, _Args...>) {
101 return _Container(ranges::begin(__range), ranges::end(__range), std::forward<_Args>(__args)...);
102 }
103
104 // Case 4 -- default-construct (or construct from the extra arguments) and insert, reserving the size if possible.
105 else if constexpr (constructible_from<_Container, _Args...> &&
106 __container_appendable<_Container, range_reference_t<_Range>>) {
107 _Container __result(std::forward<_Args>(__args)...);
108 if constexpr (sized_range<_Range> && __reservable_container<_Container>) {
109 __result.reserve(static_cast<range_size_t<_Container>>(ranges::size(__range)));
110 }
111
112 for (auto&& __ref : __range) {
113 using _Ref = decltype(__ref);
114 if constexpr (requires { __result.emplace_back(std::declval<_Ref>()); }) {
115 __result.emplace_back(std::forward<_Ref>(__ref));
116 } else if constexpr (requires { __result.push_back(std::declval<_Ref>()); }) {
117 __result.push_back(std::forward<_Ref>(__ref));
118 } else if constexpr (requires { __result.emplace(__result.end(), std::declval<_Ref>()); }) {
119 __result.emplace(__result.end(), std::forward<_Ref>(__ref));
120 } else {
121 static_assert(requires { __result.insert(__result.end(), std::declval<_Ref>()); });
122 __result.insert(__result.end(), std::forward<_Ref>(__ref));
123 }
124 }
125 return __result;
126
127 } else {
128 static_assert(__always_false<_Container>, "ranges::to: unable to convert to the given container type.");
129 }
130
131 // Try the recursive case.
132 } else if constexpr (input_range<range_reference_t<_Range>>) {
133 return ranges::to<_Container>(
134 ref_view(__range) | views::transform([](auto&& __elem) {
135 return ranges::to<range_value_t<_Container>>(std::forward<decltype(__elem)>(__elem));
136 }),
137 std::forward<_Args>(__args)...);
138
139 } else {
140 static_assert(__always_false<_Container>, "ranges::to: unable to convert to the given container type.");
141 }
142 }
143
144 template <class _Range>
145 struct __minimal_input_iterator {
146 using iterator_category = input_iterator_tag;
147 using value_type = range_value_t<_Range>;
148 using difference_type = ptrdiff_t;
149 using pointer = add_pointer_t<range_reference_t<_Range>>;
150 using reference = range_reference_t<_Range>;
151
152 reference operator*() const;
153 pointer operator->() const;
154 __minimal_input_iterator& operator++();
155 __minimal_input_iterator operator++(int);
156 bool operator==(const __minimal_input_iterator&) const;
157 };
158
159 // Deduces the full type of the container from the given template template parameter.
160 template <template <class...> class _Container, input_range _Range, class... _Args>
161 struct _Deducer {
__deduce_func_Deducer162 _LIBCPP_HIDE_FROM_ABI static constexpr auto __deduce_func() {
163 using _InputIter = __minimal_input_iterator<_Range>;
164
165 // Case 1 -- can construct directly from the given range.
166 if constexpr (requires { _Container(std::declval<_Range>(), std::declval<_Args>()...); }) {
167 using _Result = decltype( //
168 _Container(std::declval<_Range>(), std::declval<_Args>()...));
169 return type_identity<_Result>{};
170
171 // Case 2 -- can construct from the given range using the `from_range_t` tagged constructor.
172 } else if constexpr ( //
173 requires { _Container(from_range, std::declval<_Range>(), std::declval<_Args>()...); }) {
174 using _Result = //
175 decltype(_Container(from_range, std::declval<_Range>(), std::declval<_Args>()...));
176 return type_identity<_Result>{};
177
178 // Case 3 -- can construct from a begin-end iterator pair.
179 } else if constexpr ( //
180 requires { _Container(std::declval<_InputIter>(), std::declval<_InputIter>(), std::declval<_Args>()...); }) {
181 using _Result =
182 decltype(_Container(std::declval<_InputIter>(), std::declval<_InputIter>(), std::declval<_Args>()...));
183 return type_identity<_Result>{};
184
185 } else {
186 static_assert(__always_false<_Range>,
187 "ranges::to: unable to deduce the container type from the template template argument.");
188 }
189 }
190
191 using type = typename decltype(__deduce_func())::type;
192 };
193
194 // `ranges::to` specialization -- `_Container` is a template template parameter requiring deduction to figure out the
195 // container element type.
196 template <template <class...> class _Container, input_range _Range, class... _Args>
to(_Range && __range,_Args &&...__args)197 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto to(_Range&& __range, _Args&&... __args) {
198 using _DeduceExpr = typename _Deducer<_Container, _Range, _Args...>::type;
199 return ranges::to<_DeduceExpr>(std::forward<_Range>(__range), std::forward<_Args>(__args)...);
200 }
201
202 // Range adaptor closure object 1 -- wrapping the `ranges::to` version where `_Container` is a simple type template
203 // parameter.
204 template <class _Container, class... _Args>
205 requires(!view<_Container>)
to(_Args &&...__args)206 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto to(_Args&&... __args) {
207 // Mandates: C is a cv-unqualified class type.
208 static_assert(!is_const_v<_Container>, "The target container cannot be const-qualified, please remove the const");
209 static_assert(
210 !is_volatile_v<_Container>, "The target container cannot be volatile-qualified, please remove the volatile");
211
212 auto __to_func = []<input_range _Range, class... _Tail>(_Range&& __range, _Tail&&... __tail) static
213 requires requires { //
214 /**/ ranges::to<_Container>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...);
215 }
216 { return ranges::to<_Container>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...); };
217
218 return __pipeable(std::__bind_back(__to_func, std::forward<_Args>(__args)...));
219 }
220
221 // Range adaptor closure object 2 -- wrapping the `ranges::to` version where `_Container` is a template template
222 // parameter.
223 template <template <class...> class _Container, class... _Args>
to(_Args &&...__args)224 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto to(_Args&&... __args) {
225 // clang-format off
226 auto __to_func = []<input_range _Range, class... _Tail,
227 class _DeducedExpr = typename _Deducer<_Container, _Range, _Tail...>::type>
228 (_Range&& __range, _Tail&& ... __tail) static
229 requires requires { //
230 /**/ ranges::to<_DeducedExpr>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...);
231 }
232 {
233 return ranges::to<_DeducedExpr>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...);
234 };
235 // clang-format on
236
237 return __pipeable(std::__bind_back(__to_func, std::forward<_Args>(__args)...));
238 }
239
240 } // namespace ranges
241
242 #endif // _LIBCPP_STD_VER >= 23
243
244 _LIBCPP_END_NAMESPACE_STD
245
246 #endif // _LIBCPP___RANGES_TO_H
247