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