v1/__ranges/elements_view.h

0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===----------------------------------------------------------------------===//
0009
0010 #ifndef _LIBCPP___RANGES_ELEMENTS_VIEW_H
0011 #define _LIBCPP___RANGES_ELEMENTS_VIEW_H
0012
0013 #include <__compare/three_way_comparable.h>
0014 #include <__concepts/constructible.h>
0015 #include <__concepts/convertible_to.h>
0016 #include <__concepts/derived_from.h>
0017 #include <__concepts/equality_comparable.h>
0018 #include <__config>
0019 #include <__fwd/get.h>
0020 #include <__iterator/concepts.h>
0021 #include <__iterator/iterator_traits.h>
0022 #include <__ranges/access.h>
0023 #include <__ranges/all.h>
0024 #include <__ranges/concepts.h>
0025 #include <__ranges/enable_borrowed_range.h>
0026 #include <__ranges/range_adaptor.h>
0027 #include <__ranges/size.h>
0028 #include <__ranges/view_interface.h>
0029 #include <__tuple/tuple_element.h>
0030 #include <__tuple/tuple_like.h>
0031 #include <__tuple/tuple_size.h>
0032 #include <__type_traits/is_reference.h>
0033 #include <__type_traits/maybe_const.h>
0034 #include <__type_traits/remove_cv.h>
0035 #include <__type_traits/remove_cvref.h>
0036 #include <__type_traits/remove_reference.h>
0037 #include <__utility/declval.h>
0038 #include <__utility/forward.h>
0039 #include <__utility/move.h>
0040 #include <tuple> // std::get
0041
0042 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0043 #  pragma GCC system_header
0044 #endif
0045
0046 _LIBCPP_PUSH_MACROS
0047 #include <__undef_macros>
0048
0049 _LIBCPP_BEGIN_NAMESPACE_STD
0050
0051 #if _LIBCPP_STD_VER >= 20
0052
0053 namespace ranges {
0054
0055 template <class _Tp, size_t _Np>
0056 concept __has_tuple_element = __tuple_like<_Tp> && _Np < tuple_size<_Tp>::value;
0057
0058 template <class _Tp, size_t _Np>
0059 concept __returnable_element = is_reference_v<_Tp> || move_constructible<tuple_element_t<_Np, _Tp>>;
0060
0061 template <input_range _View, size_t _Np>
0062   requires view<_View> && __has_tuple_element<range_value_t<_View>, _Np> &&
0063            __has_tuple_element<remove_reference_t<range_reference_t<_View>>, _Np> &&
0064            __returnable_element<range_reference_t<_View>, _Np>
0065 class elements_view : public view_interface<elements_view<_View, _Np>> {
0066 private:
0067   template <bool>
0068   class __iterator;
0069
0070   template <bool>
0071   class __sentinel;
0072
0073 public:
0074   _LIBCPP_HIDE_FROM_ABI elements_view()
0075     requires default_initializable<_View>
0076   = default;
0077
0078   _LIBCPP_HIDE_FROM_ABI constexpr explicit elements_view(_View __base) : __base_(std::move(__base)) {}
0079
0080   _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
0081     requires copy_constructible<_View>
0082   {
0083     return __base_;
0084   }
0085
0086   _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
0087
0088   _LIBCPP_HIDE_FROM_ABI constexpr auto begin()
0089     requires(!__simple_view<_View>)
0090   {
0091     return __iterator</*_Const=*/false>(ranges::begin(__base_));
0092   }
0093
0094   _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
0095     requires range<const _View>
0096   {
0097     return __iterator</*_Const=*/true>(ranges::begin(__base_));
0098   }
0099
0100   _LIBCPP_HIDE_FROM_ABI constexpr auto end()
0101     requires(!__simple_view<_View> && !common_range<_View>)
0102   {
0103     return __sentinel</*_Const=*/false>{ranges::end(__base_)};
0104   }
0105
0106   _LIBCPP_HIDE_FROM_ABI constexpr auto end()
0107     requires(!__simple_view<_View> && common_range<_View>)
0108   {
0109     return __iterator</*_Const=*/false>{ranges::end(__base_)};
0110   }
0111
0112   _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
0113     requires range<const _View>
0114   {
0115     return __sentinel</*_Const=*/true>{ranges::end(__base_)};
0116   }
0117
0118   _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
0119     requires common_range<const _View>
0120   {
0121     return __iterator</*_Const=*/true>{ranges::end(__base_)};
0122   }
0123
0124   _LIBCPP_HIDE_FROM_ABI constexpr auto size()
0125     requires sized_range<_View>
0126   {
0127     return ranges::size(__base_);
0128   }
0129
0130   _LIBCPP_HIDE_FROM_ABI constexpr auto size() const
0131     requires sized_range<const _View>
0132   {
0133     return ranges::size(__base_);
0134   }
0135
0136 private:
0137   _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
0138 };
0139
0140 template <class, size_t>
0141 struct __elements_view_iterator_category_base {};
0142
0143 template <forward_range _Base, size_t _Np>
0144 struct __elements_view_iterator_category_base<_Base, _Np> {
0145   static consteval auto __get_iterator_category() {
0146     using _Result = decltype(std::get<_Np>(*std::declval<iterator_t<_Base>>()));
0147     using _Cat    = typename iterator_traits<iterator_t<_Base>>::iterator_category;
0148
0149     if constexpr (!is_lvalue_reference_v<_Result>) {
0150       return input_iterator_tag{};
0151     } else if constexpr (derived_from<_Cat, random_access_iterator_tag>) {
0152       return random_access_iterator_tag{};
0153     } else {
0154       return _Cat{};
0155     }
0156   }
0157
0158   using iterator_category = decltype(__get_iterator_category());
0159 };
0160
0161 template <input_range _View, size_t _Np>
0162   requires view<_View> && __has_tuple_element<range_value_t<_View>, _Np> &&
0163            __has_tuple_element<remove_reference_t<range_reference_t<_View>>, _Np> &&
0164            __returnable_element<range_reference_t<_View>, _Np>
0165 template <bool _Const>
0166 class elements_view<_View, _Np>::__iterator
0167     : public __elements_view_iterator_category_base<__maybe_const<_Const, _View>, _Np> {
0168   template <bool>
0169   friend class __iterator;
0170
0171   template <bool>
0172   friend class __sentinel;
0173
0174   using _Base _LIBCPP_NODEBUG = __maybe_const<_Const, _View>;
0175
0176   iterator_t<_Base> __current_ = iterator_t<_Base>();
0177
0178   _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto) __get_element(const iterator_t<_Base>& __i) {
0179     if constexpr (is_reference_v<range_reference_t<_Base>>) {
0180       return std::get<_Np>(*__i);
0181     } else {
0182       using _Element = remove_cv_t<tuple_element_t<_Np, range_reference_t<_Base>>>;
0183       return static_cast<_Element>(std::get<_Np>(*__i));
0184     }
0185   }
0186
0187   static consteval auto __get_iterator_concept() {
0188     if constexpr (random_access_range<_Base>) {
0189       return random_access_iterator_tag{};
0190     } else if constexpr (bidirectional_range<_Base>) {
0191       return bidirectional_iterator_tag{};
0192     } else if constexpr (forward_range<_Base>) {
0193       return forward_iterator_tag{};
0194     } else {
0195       return input_iterator_tag{};
0196     }
0197   }
0198
0199 public:
0200   using iterator_concept = decltype(__get_iterator_concept());
0201   using value_type       = remove_cvref_t<tuple_element_t<_Np, range_value_t<_Base>>>;
0202   using difference_type  = range_difference_t<_Base>;
0203
0204   _LIBCPP_HIDE_FROM_ABI __iterator()
0205     requires default_initializable<iterator_t<_Base>>
0206   = default;
0207
0208   _LIBCPP_HIDE_FROM_ABI constexpr explicit __iterator(iterator_t<_Base> __current) : __current_(std::move(__current)) {}
0209
0210   _LIBCPP_HIDE_FROM_ABI constexpr __iterator(__iterator<!_Const> __i)
0211     requires _Const && convertible_to<iterator_t<_View>, iterator_t<_Base>>
0212       : __current_(std::move(__i.__current_)) {}
0213
0214   _LIBCPP_HIDE_FROM_ABI constexpr const iterator_t<_Base>& base() const& noexcept { return __current_; }
0215
0216   _LIBCPP_HIDE_FROM_ABI constexpr iterator_t<_Base> base() && { return std::move(__current_); }
0217
0218   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator*() const { return __get_element(__current_); }
0219
0220   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator++() {
0221     ++__current_;
0222     return *this;
0223   }
0224
0225   _LIBCPP_HIDE_FROM_ABI constexpr void operator++(int) { ++__current_; }
0226
0227   _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator++(int)
0228     requires forward_range<_Base>
0229   {
0230     auto __temp = *this;
0231     ++__current_;
0232     return __temp;
0233   }
0234
0235   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator--()
0236     requires bidirectional_range<_Base>
0237   {
0238     --__current_;
0239     return *this;
0240   }
0241
0242   _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator--(int)
0243     requires bidirectional_range<_Base>
0244   {
0245     auto __temp = *this;
0246     --__current_;
0247     return __temp;
0248   }
0249
0250   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator+=(difference_type __n)
0251     requires random_access_range<_Base>
0252   {
0253     __current_ += __n;
0254     return *this;
0255   }
0256
0257   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator-=(difference_type __n)
0258     requires random_access_range<_Base>
0259   {
0260     __current_ -= __n;
0261     return *this;
0262   }
0263
0264   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator[](difference_type __n) const
0265     requires random_access_range<_Base>
0266   {
0267     return __get_element(__current_ + __n);
0268   }
0269
0270   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __iterator& __x, const __iterator& __y)
0271     requires equality_comparable<iterator_t<_Base>>
0272   {
0273     return __x.__current_ == __y.__current_;
0274   }
0275
0276   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<(const __iterator& __x, const __iterator& __y)
0277     requires random_access_range<_Base>
0278   {
0279     return __x.__current_ < __y.__current_;
0280   }
0281
0282   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>(const __iterator& __x, const __iterator& __y)
0283     requires random_access_range<_Base>
0284   {
0285     return __y < __x;
0286   }
0287
0288   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<=(const __iterator& __x, const __iterator& __y)
0289     requires random_access_range<_Base>
0290   {
0291     return !(__y < __x);
0292   }
0293
0294   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>=(const __iterator& __x, const __iterator& __y)
0295     requires random_access_range<_Base>
0296   {
0297     return !(__x < __y);
0298   }
0299
0300   _LIBCPP_HIDE_FROM_ABI friend constexpr auto operator<=>(const __iterator& __x, const __iterator& __y)
0301     requires random_access_range<_Base> && three_way_comparable<iterator_t<_Base>>
0302   {
0303     return __x.__current_ <=> __y.__current_;
0304   }
0305
0306   _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator+(const __iterator& __x, difference_type __y)
0307     requires random_access_range<_Base>
0308   {
0309     return __iterator{__x} += __y;
0310   }
0311
0312   _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator+(difference_type __x, const __iterator& __y)
0313     requires random_access_range<_Base>
0314   {
0315     return __y + __x;
0316   }
0317
0318   _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator-(const __iterator& __x, difference_type __y)
0319     requires random_access_range<_Base>
0320   {
0321     return __iterator{__x} -= __y;
0322   }
0323
0324   _LIBCPP_HIDE_FROM_ABI friend constexpr difference_type operator-(const __iterator& __x, const __iterator& __y)
0325     requires sized_sentinel_for<iterator_t<_Base>, iterator_t<_Base>>
0326   {
0327     return __x.__current_ - __y.__current_;
0328   }
0329 };
0330
0331 template <input_range _View, size_t _Np>
0332   requires view<_View> && __has_tuple_element<range_value_t<_View>, _Np> &&
0333            __has_tuple_element<remove_reference_t<range_reference_t<_View>>, _Np> &&
0334            __returnable_element<range_reference_t<_View>, _Np>
0335 template <bool _Const>
0336 class elements_view<_View, _Np>::__sentinel {
0337 private:
0338   using _Base _LIBCPP_NODEBUG                        = __maybe_const<_Const, _View>;
0339   _LIBCPP_NO_UNIQUE_ADDRESS sentinel_t<_Base> __end_ = sentinel_t<_Base>();
0340
0341   template <bool>
0342   friend class __sentinel;
0343
0344   template <bool _AnyConst>
0345   _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto) __get_current(const __iterator<_AnyConst>& __iter) {
0346     return (__iter.__current_);
0347   }
0348
0349 public:
0350   _LIBCPP_HIDE_FROM_ABI __sentinel() = default;
0351
0352   _LIBCPP_HIDE_FROM_ABI constexpr explicit __sentinel(sentinel_t<_Base> __end) : __end_(std::move(__end)) {}
0353
0354   _LIBCPP_HIDE_FROM_ABI constexpr __sentinel(__sentinel<!_Const> __other)
0355     requires _Const && convertible_to<sentinel_t<_View>, sentinel_t<_Base>>
0356       : __end_(std::move(__other.__end_)) {}
0357
0358   _LIBCPP_HIDE_FROM_ABI constexpr sentinel_t<_Base> base() const { return __end_; }
0359
0360   template <bool _OtherConst>
0361     requires sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
0362   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __iterator<_OtherConst>& __x, const __sentinel& __y) {
0363     return __get_current(__x) == __y.__end_;
0364   }
0365
0366   template <bool _OtherConst>
0367     requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
0368   _LIBCPP_HIDE_FROM_ABI friend constexpr range_difference_t<__maybe_const<_OtherConst, _View>>
0369   operator-(const __iterator<_OtherConst>& __x, const __sentinel& __y) {
0370     return __get_current(__x) - __y.__end_;
0371   }
0372
0373   template <bool _OtherConst>
0374     requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
0375   _LIBCPP_HIDE_FROM_ABI friend constexpr range_difference_t<__maybe_const<_OtherConst, _View>>
0376   operator-(const __sentinel& __x, const __iterator<_OtherConst>& __y) {
0377     return __x.__end_ - __get_current(__y);
0378   }
0379 };
0380
0381 template <class _Tp, size_t _Np>
0382 inline constexpr bool enable_borrowed_range<elements_view<_Tp, _Np>> = enable_borrowed_range<_Tp>;
0383
0384 template <class _Tp>
0385 using keys_view = elements_view<_Tp, 0>;
0386 template <class _Tp>
0387 using values_view = elements_view<_Tp, 1>;
0388
0389 namespace views {
0390 namespace __elements {
0391
0392 template <size_t _Np>
0393 struct __fn : __range_adaptor_closure<__fn<_Np>> {
0394   template <class _Range>
0395   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range) const
0396       /**/ noexcept(noexcept(elements_view<all_t<_Range&&>, _Np>(std::forward<_Range>(__range))))
0397       /*------*/ -> decltype(elements_view<all_t<_Range&&>, _Np>(std::forward<_Range>(__range))) {
0398     /*-------------*/ return elements_view<all_t<_Range&&>, _Np>(std::forward<_Range>(__range));
0399   }
0400 };
0401 } // namespace __elements
0402
0403 inline namespace __cpo {
0404 template <size_t _Np>
0405 inline constexpr auto elements = __elements::__fn<_Np>{};
0406 inline constexpr auto keys     = elements<0>;
0407 inline constexpr auto values   = elements<1>;
0408 } // namespace __cpo
0409 } // namespace views
0410 } // namespace ranges
0411
0412 #endif // _LIBCPP_STD_VER >= 20
0413
0414 _LIBCPP_END_NAMESPACE_STD
0415
0416 _LIBCPP_POP_MACROS
0417
0418 #endif // _LIBCPP___RANGES_ELEMENTS_VIEW_H