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