libcxx/include/__ranges/elements_view.h

   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_ELEMENTS_VIEW_H
  11 #define _LIBCPP___RANGES_ELEMENTS_VIEW_H
  12
  13 #include <__compare/three_way_comparable.h>
  14 #include <__concepts/constructible.h>
  15 #include <__concepts/convertible_to.h>
  16 #include <__concepts/derived_from.h>
  17 #include <__concepts/equality_comparable.h>
  18 #include <__config>
  19 #include <__fwd/get.h>
  20 #include <__iterator/concepts.h>
  21 #include <__iterator/iterator_traits.h>
  22 #include <__ranges/access.h>
  23 #include <__ranges/all.h>
  24 #include <__ranges/concepts.h>
  25 #include <__ranges/enable_borrowed_range.h>
  26 #include <__ranges/range_adaptor.h>
  27 #include <__ranges/size.h>
  28 #include <__ranges/view_interface.h>
  29 #include <__tuple/tuple_element.h>
  30 #include <__tuple/tuple_like.h>
  31 #include <__tuple/tuple_size.h>
  32 #include <__type_traits/is_reference.h>
  33 #include <__type_traits/maybe_const.h>
  34 #include <__type_traits/remove_cv.h>
  35 #include <__type_traits/remove_cvref.h>
  36 #include <__type_traits/remove_reference.h>
  37 #include <__utility/declval.h>
  38 #include <__utility/forward.h>
  39 #include <__utility/move.h>
  40 #include <cstddef>
  41
  42 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  43 #  pragma GCC system_header
  44 #endif
  45
  46 _LIBCPP_BEGIN_NAMESPACE_STD
  47
  48 #if _LIBCPP_STD_VER >= 20
  49
  50 namespace ranges {
  51
  52 template <class _Tp, size_t _Np>
  53 concept __has_tuple_element = __tuple_like<_Tp> && _Np < tuple_size<_Tp>::value;
  54
  55 template <class _Tp, size_t _Np>
  56 concept __returnable_element = is_reference_v<_Tp> || move_constructible<tuple_element_t<_Np, _Tp>>;
  57
  58 template <input_range _View, size_t _Np>
  59   requires view<_View> && __has_tuple_element<range_value_t<_View>, _Np> &&
  60            __has_tuple_element<remove_reference_t<range_reference_t<_View>>, _Np> &&
  61            __returnable_element<range_reference_t<_View>, _Np>
  62 class elements_view : public view_interface<elements_view<_View, _Np>> {
  63 private:
  64   template <bool>
  65   class __iterator;
  66
  67   template <bool>
  68   class __sentinel;
  69
  70 public:
  71   _LIBCPP_HIDE_FROM_ABI elements_view()
  72     requires default_initializable<_View>
  73   = default;
  74
  75   _LIBCPP_HIDE_FROM_ABI constexpr explicit elements_view(_View __base) : __base_(std::move(__base)) {}
  76
  77   _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
  78     requires copy_constructible<_View>
  79   {
  80     return __base_;
  81   }
  82
  83   _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
  84
  85   _LIBCPP_HIDE_FROM_ABI constexpr auto begin()
  86     requires(!__simple_view<_View>)
  87   {
  88     return __iterator</*_Const=*/false>(ranges::begin(__base_));
  89   }
  90
  91   _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
  92     requires range<const _View>
  93   {
  94     return __iterator</*_Const=*/true>(ranges::begin(__base_));
  95   }
  96
  97   _LIBCPP_HIDE_FROM_ABI constexpr auto end()
  98     requires(!__simple_view<_View> && !common_range<_View>)
  99   {
 100     return __sentinel</*_Const=*/false>{ranges::end(__base_)};
 101   }
 102
 103   _LIBCPP_HIDE_FROM_ABI constexpr auto end()
 104     requires(!__simple_view<_View> && common_range<_View>)
 105   {
 106     return __iterator</*_Const=*/false>{ranges::end(__base_)};
 107   }
 108
 109   _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
 110     requires range<const _View>
 111   {
 112     return __sentinel</*_Const=*/true>{ranges::end(__base_)};
 113   }
 114
 115   _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
 116     requires common_range<const _View>
 117   {
 118     return __iterator</*_Const=*/true>{ranges::end(__base_)};
 119   }
 120
 121   _LIBCPP_HIDE_FROM_ABI constexpr auto size()
 122     requires sized_range<_View>
 123   {
 124     return ranges::size(__base_);
 125   }
 126
 127   _LIBCPP_HIDE_FROM_ABI constexpr auto size() const
 128     requires sized_range<const _View>
 129   {
 130     return ranges::size(__base_);
 131   }
 132
 133 private:
 134   _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
 135 };
 136
 137 template <class, size_t>
 138 struct __elements_view_iterator_category_base {};
 139
 140 template <forward_range _Base, size_t _Np>
 141 struct __elements_view_iterator_category_base<_Base, _Np> {
 142   static consteval auto __get_iterator_category() {
 143     using _Result = decltype(std::get<_Np>(*std::declval<iterator_t<_Base>>()));
 144     using _Cat    = typename iterator_traits<iterator_t<_Base>>::iterator_category;
 145
 146     if constexpr (!is_lvalue_reference_v<_Result>) {
 147       return input_iterator_tag{};
 148     } else if constexpr (derived_from<_Cat, random_access_iterator_tag>) {
 149       return random_access_iterator_tag{};
 150     } else {
 151       return _Cat{};
 152     }
 153   }
 154
 155   using iterator_category = decltype(__get_iterator_category());
 156 };
 157
 158 template <input_range _View, size_t _Np>
 159   requires view<_View> && __has_tuple_element<range_value_t<_View>, _Np> &&
 160            __has_tuple_element<remove_reference_t<range_reference_t<_View>>, _Np> &&
 161            __returnable_element<range_reference_t<_View>, _Np>
 162 template <bool _Const>
 163 class elements_view<_View, _Np>::__iterator
 164     : public __elements_view_iterator_category_base<__maybe_const<_Const, _View>, _Np> {
 165   template <bool>
 166   friend class __iterator;
 167
 168   template <bool>
 169   friend class __sentinel;
 170
 171   using _Base = __maybe_const<_Const, _View>;
 172
 173   iterator_t<_Base> __current_ = iterator_t<_Base>();
 174
 175   _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto) __get_element(const iterator_t<_Base>& __i) {
 176     if constexpr (is_reference_v<range_reference_t<_Base>>) {
 177       return std::get<_Np>(*__i);
 178     } else {
 179       using _Element = remove_cv_t<tuple_element_t<_Np, range_reference_t<_Base>>>;
 180       return static_cast<_Element>(std::get<_Np>(*__i));
 181     }
 182   }
 183
 184   static consteval auto __get_iterator_concept() {
 185     if constexpr (random_access_range<_Base>) {
 186       return random_access_iterator_tag{};
 187     } else if constexpr (bidirectional_range<_Base>) {
 188       return bidirectional_iterator_tag{};
 189     } else if constexpr (forward_range<_Base>) {
 190       return forward_iterator_tag{};
 191     } else {
 192       return input_iterator_tag{};
 193     }
 194   }
 195
 196 public:
 197   using iterator_concept = decltype(__get_iterator_concept());
 198   using value_type       = remove_cvref_t<tuple_element_t<_Np, range_value_t<_Base>>>;
 199   using difference_type  = range_difference_t<_Base>;
 200
 201   _LIBCPP_HIDE_FROM_ABI __iterator()
 202     requires default_initializable<iterator_t<_Base>>
 203   = default;
 204
 205   _LIBCPP_HIDE_FROM_ABI constexpr explicit __iterator(iterator_t<_Base> __current) : __current_(std::move(__current)) {}
 206
 207   _LIBCPP_HIDE_FROM_ABI constexpr __iterator(__iterator<!_Const> __i)
 208     requires _Const && convertible_to<iterator_t<_View>, iterator_t<_Base>>
 209       : __current_(std::move(__i.__current_)) {}
 210
 211   _LIBCPP_HIDE_FROM_ABI constexpr const iterator_t<_Base>& base() const& noexcept { return __current_; }
 212
 213   _LIBCPP_HIDE_FROM_ABI constexpr iterator_t<_Base> base() && { return std::move(__current_); }
 214
 215   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator*() const { return __get_element(__current_); }
 216
 217   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator++() {
 218     ++__current_;
 219     return *this;
 220   }
 221
 222   _LIBCPP_HIDE_FROM_ABI constexpr void operator++(int) { ++__current_; }
 223
 224   _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator++(int)
 225     requires forward_range<_Base>
 226   {
 227     auto __temp = *this;
 228     ++__current_;
 229     return __temp;
 230   }
 231
 232   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator--()
 233     requires bidirectional_range<_Base>
 234   {
 235     --__current_;
 236     return *this;
 237   }
 238
 239   _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator--(int)
 240     requires bidirectional_range<_Base>
 241   {
 242     auto __temp = *this;
 243     --__current_;
 244     return __temp;
 245   }
 246
 247   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator+=(difference_type __n)
 248     requires random_access_range<_Base>
 249   {
 250     __current_ += __n;
 251     return *this;
 252   }
 253
 254   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator-=(difference_type __n)
 255     requires random_access_range<_Base>
 256   {
 257     __current_ -= __n;
 258     return *this;
 259   }
 260
 261   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator[](difference_type __n) const
 262     requires random_access_range<_Base>
 263   {
 264     return __get_element(__current_ + __n);
 265   }
 266
 267   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __iterator& __x, const __iterator& __y)
 268     requires equality_comparable<iterator_t<_Base>>
 269   {
 270     return __x.__current_ == __y.__current_;
 271   }
 272
 273   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<(const __iterator& __x, const __iterator& __y)
 274     requires random_access_range<_Base>
 275   {
 276     return __x.__current_ < __y.__current_;
 277   }
 278
 279   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>(const __iterator& __x, const __iterator& __y)
 280     requires random_access_range<_Base>
 281   {
 282     return __y < __x;
 283   }
 284
 285   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<=(const __iterator& __x, const __iterator& __y)
 286     requires random_access_range<_Base>
 287   {
 288     return !(__y < __x);
 289   }
 290
 291   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>=(const __iterator& __x, const __iterator& __y)
 292     requires random_access_range<_Base>
 293   {
 294     return !(__x < __y);
 295   }
 296
 297   _LIBCPP_HIDE_FROM_ABI friend constexpr auto operator<=>(const __iterator& __x, const __iterator& __y)
 298     requires random_access_range<_Base> && three_way_comparable<iterator_t<_Base>>
 299   {
 300     return __x.__current_ <=> __y.__current_;
 301   }
 302
 303   _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator+(const __iterator& __x, difference_type __y)
 304     requires random_access_range<_Base>
 305   {
 306     return __iterator{__x} += __y;
 307   }
 308
 309   _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator+(difference_type __x, const __iterator& __y)
 310     requires random_access_range<_Base>
 311   {
 312     return __y + __x;
 313   }
 314
 315   _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator-(const __iterator& __x, difference_type __y)
 316     requires random_access_range<_Base>
 317   {
 318     return __iterator{__x} -= __y;
 319   }
 320
 321   _LIBCPP_HIDE_FROM_ABI friend constexpr difference_type operator-(const __iterator& __x, const __iterator& __y)
 322     requires sized_sentinel_for<iterator_t<_Base>, iterator_t<_Base>>
 323   {
 324     return __x.__current_ - __y.__current_;
 325   }
 326 };
 327
 328 template <input_range _View, size_t _Np>
 329   requires view<_View> && __has_tuple_element<range_value_t<_View>, _Np> &&
 330            __has_tuple_element<remove_reference_t<range_reference_t<_View>>, _Np> &&
 331            __returnable_element<range_reference_t<_View>, _Np>
 332 template <bool _Const>
 333 class elements_view<_View, _Np>::__sentinel {
 334 private:
 335   using _Base                                        = __maybe_const<_Const, _View>;
 336   _LIBCPP_NO_UNIQUE_ADDRESS sentinel_t<_Base> __end_ = sentinel_t<_Base>();
 337
 338   template <bool>
 339   friend class __sentinel;
 340
 341   template <bool _AnyConst>
 342   _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto) __get_current(const __iterator<_AnyConst>& __iter) {
 343     return (__iter.__current_);
 344   }
 345
 346 public:
 347   _LIBCPP_HIDE_FROM_ABI __sentinel() = default;
 348
 349   _LIBCPP_HIDE_FROM_ABI constexpr explicit __sentinel(sentinel_t<_Base> __end) : __end_(std::move(__end)) {}
 350
 351   _LIBCPP_HIDE_FROM_ABI constexpr __sentinel(__sentinel<!_Const> __other)
 352     requires _Const && convertible_to<sentinel_t<_View>, sentinel_t<_Base>>
 353       : __end_(std::move(__other.__end_)) {}
 354
 355   _LIBCPP_HIDE_FROM_ABI constexpr sentinel_t<_Base> base() const { return __end_; }
 356
 357   template <bool _OtherConst>
 358     requires sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
 359   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __iterator<_OtherConst>& __x, const __sentinel& __y) {
 360     return __get_current(__x) == __y.__end_;
 361   }
 362
 363   template <bool _OtherConst>
 364     requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
 365   _LIBCPP_HIDE_FROM_ABI friend constexpr range_difference_t<__maybe_const<_OtherConst, _View>>
 366   operator-(const __iterator<_OtherConst>& __x, const __sentinel& __y) {
 367     return __get_current(__x) - __y.__end_;
 368   }
 369
 370   template <bool _OtherConst>
 371     requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
 372   _LIBCPP_HIDE_FROM_ABI friend constexpr range_difference_t<__maybe_const<_OtherConst, _View>>
 373   operator-(const __sentinel& __x, const __iterator<_OtherConst>& __y) {
 374     return __x.__end_ - __get_current(__y);
 375   }
 376 };
 377
 378 template <class _Tp, size_t _Np>
 379 inline constexpr bool enable_borrowed_range<elements_view<_Tp, _Np>> = enable_borrowed_range<_Tp>;
 380
 381 template <class _Tp>
 382 using keys_view = elements_view<_Tp, 0>;
 383 template <class _Tp>
 384 using values_view = elements_view<_Tp, 1>;
 385
 386 namespace views {
 387 namespace __elements {
 388
 389 template <size_t _Np>
 390 struct __fn : __range_adaptor_closure<__fn<_Np>> {
 391   template <class _Range>
 392   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range) const
 393       /**/ noexcept(noexcept(elements_view<all_t<_Range&&>, _Np>(std::forward<_Range>(__range))))
 394       /*------*/ -> decltype(elements_view<all_t<_Range&&>, _Np>(std::forward<_Range>(__range))) {
 395     /*-------------*/ return elements_view<all_t<_Range&&>, _Np>(std::forward<_Range>(__range));
 396   }
 397 };
 398 } // namespace __elements
 399
 400 inline namespace __cpo {
 401 template <size_t _Np>
 402 inline constexpr auto elements = __elements::__fn<_Np>{};
 403 inline constexpr auto keys     = elements<0>;
 404 inline constexpr auto values   = elements<1>;
 405 } // namespace __cpo
 406 } // namespace views
 407 } // namespace ranges
 408
 409 #endif // _LIBCPP_STD_VER >= 20
 410
 411 _LIBCPP_END_NAMESPACE_STD
 412
 413 #endif // _LIBCPP___RANGES_ELEMENTS_VIEW_H