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 = 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> 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>) 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 { 162 _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> 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>) 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> 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