libcxx/include/__ranges/transform_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_TRANSFORM_VIEW_H
  11 #define _LIBCPP___RANGES_TRANSFORM_VIEW_H
  12
  13 #include <__compare/three_way_comparable.h>
  14 #include <__concepts/constructible.h>
  15 #include <__concepts/convertible_to.h>
  16 #include <__concepts/copyable.h>
  17 #include <__concepts/derived_from.h>
  18 #include <__concepts/equality_comparable.h>
  19 #include <__concepts/invocable.h>
  20 #include <__config>
  21 #include <__functional/bind_back.h>
  22 #include <__functional/invoke.h>
  23 #include <__functional/perfect_forward.h>
  24 #include <__iterator/concepts.h>
  25 #include <__iterator/iterator_traits.h>
  26 #include <__memory/addressof.h>
  27 #include <__ranges/access.h>
  28 #include <__ranges/all.h>
  29 #include <__ranges/concepts.h>
  30 #include <__ranges/empty.h>
  31 #include <__ranges/movable_box.h>
  32 #include <__ranges/range_adaptor.h>
  33 #include <__ranges/size.h>
  34 #include <__ranges/view_interface.h>
  35 #include <__type_traits/conditional.h>
  36 #include <__type_traits/decay.h>
  37 #include <__type_traits/invoke.h>
  38 #include <__type_traits/is_nothrow_constructible.h>
  39 #include <__type_traits/is_object.h>
  40 #include <__type_traits/is_reference.h>
  41 #include <__type_traits/maybe_const.h>
  42 #include <__type_traits/remove_cvref.h>
  43 #include <__utility/forward.h>
  44 #include <__utility/in_place.h>
  45 #include <__utility/move.h>
  46
  47 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  48 #  pragma GCC system_header
  49 #endif
  50
  51 _LIBCPP_PUSH_MACROS
  52 #include <__undef_macros>
  53
  54 _LIBCPP_BEGIN_NAMESPACE_STD
  55
  56 #if _LIBCPP_STD_VER >= 20
  57
  58 namespace ranges {
  59
  60 template <class _Fn, class _View>
  61 concept __regular_invocable_with_range_ref = regular_invocable<_Fn, range_reference_t<_View>>;
  62
  63 template <class _View, class _Fn>
  64 concept __transform_view_constraints =
  65     view<_View> && is_object_v<_Fn> && regular_invocable<_Fn&, range_reference_t<_View>> &&
  66     __can_reference<invoke_result_t<_Fn&, range_reference_t<_View>>>;
  67
  68 #  if _LIBCPP_STD_VER >= 23
  69 template <input_range _View, move_constructible _Fn>
  70 #  else
  71 template <input_range _View, copy_constructible _Fn>
  72 #  endif
  73   requires __transform_view_constraints<_View, _Fn>
  74 class _LIBCPP_ABI_LLVM18_NO_UNIQUE_ADDRESS transform_view : public view_interface<transform_view<_View, _Fn>> {
  75   template <bool>
  76   class __iterator;
  77   template <bool>
  78   class __sentinel;
  79
  80   _LIBCPP_NO_UNIQUE_ADDRESS __movable_box<_Fn> __func_;
  81   _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
  82
  83 public:
  84   _LIBCPP_HIDE_FROM_ABI transform_view()
  85     requires default_initializable<_View> && default_initializable<_Fn>
  86   = default;
  87
  88   _LIBCPP_HIDE_FROM_ABI constexpr _LIBCPP_EXPLICIT_SINCE_CXX23 transform_view(_View __base, _Fn __func)
  89       : __func_(std::in_place, std::move(__func)), __base_(std::move(__base)) {}
  90
  91   _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
  92     requires copy_constructible<_View>
  93   {
  94     return __base_;
  95   }
  96   _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
  97
  98   _LIBCPP_HIDE_FROM_ABI constexpr __iterator<false> begin() { return __iterator<false>{*this, ranges::begin(__base_)}; }
  99   _LIBCPP_HIDE_FROM_ABI constexpr __iterator<true> begin() const
 100     requires range<const _View> && __regular_invocable_with_range_ref<const _Fn&, const _View>
 101   {
 102     return __iterator<true>(*this, ranges::begin(__base_));
 103   }
 104
 105   _LIBCPP_HIDE_FROM_ABI constexpr __sentinel<false> end() { return __sentinel<false>(ranges::end(__base_)); }
 106   _LIBCPP_HIDE_FROM_ABI constexpr __iterator<false> end()
 107     requires common_range<_View>
 108   {
 109     return __iterator<false>(*this, ranges::end(__base_));
 110   }
 111   _LIBCPP_HIDE_FROM_ABI constexpr __sentinel<true> end() const
 112     requires range<const _View> && __regular_invocable_with_range_ref<const _Fn&, const _View>
 113   {
 114     return __sentinel<true>(ranges::end(__base_));
 115   }
 116   _LIBCPP_HIDE_FROM_ABI constexpr __iterator<true> end() const
 117     requires common_range<const _View> && __regular_invocable_with_range_ref<const _Fn&, const _View>
 118   {
 119     return __iterator<true>(*this, ranges::end(__base_));
 120   }
 121
 122   _LIBCPP_HIDE_FROM_ABI constexpr auto size()
 123     requires sized_range<_View>
 124   {
 125     return ranges::size(__base_);
 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
 134 template <class _Range, class _Fn>
 135 transform_view(_Range&&, _Fn) -> transform_view<views::all_t<_Range>, _Fn>;
 136
 137 template <class _View>
 138 struct __transform_view_iterator_concept {
 139   using type = input_iterator_tag;
 140 };
 141
 142 template <random_access_range _View>
 143 struct __transform_view_iterator_concept<_View> {
 144   using type = random_access_iterator_tag;
 145 };
 146
 147 template <bidirectional_range _View>
 148 struct __transform_view_iterator_concept<_View> {
 149   using type = bidirectional_iterator_tag;
 150 };
 151
 152 template <forward_range _View>
 153 struct __transform_view_iterator_concept<_View> {
 154   using type = forward_iterator_tag;
 155 };
 156
 157 template <class, class>
 158 struct __transform_view_iterator_category_base {};
 159
 160 template <forward_range _View, class _Fn>
 161 struct __transform_view_iterator_category_base<_View, _Fn> {
 162   using _Cat = typename iterator_traits<iterator_t<_View>>::iterator_category;
 163
 164   using iterator_category =
 165       conditional_t< is_reference_v<invoke_result_t<_Fn&, range_reference_t<_View>>>,
 166                      conditional_t< derived_from<_Cat, contiguous_iterator_tag>, random_access_iterator_tag, _Cat >,
 167                      input_iterator_tag >;
 168 };
 169
 170 #  if _LIBCPP_STD_VER >= 23
 171 template <input_range _View, move_constructible _Fn>
 172 #  else
 173 template <input_range _View, copy_constructible _Fn>
 174 #  endif
 175   requires __transform_view_constraints<_View, _Fn>
 176 template <bool _Const>
 177 class transform_view<_View, _Fn>::__iterator
 178     : public __transform_view_iterator_category_base<_View, __maybe_const<_Const, _Fn>> {
 179
 180   using _Parent = __maybe_const<_Const, transform_view>;
 181   using _Base   = __maybe_const<_Const, _View>;
 182
 183   _Parent* __parent_ = nullptr;
 184
 185   template <bool>
 186   friend class transform_view<_View, _Fn>::__iterator;
 187
 188   template <bool>
 189   friend class transform_view<_View, _Fn>::__sentinel;
 190
 191 public:
 192   iterator_t<_Base> __current_ = iterator_t<_Base>();
 193
 194   using iterator_concept = typename __transform_view_iterator_concept<_View>::type;
 195   using value_type       = remove_cvref_t<invoke_result_t<__maybe_const<_Const, _Fn>&, range_reference_t<_Base>>>;
 196   using difference_type  = range_difference_t<_Base>;
 197
 198   _LIBCPP_HIDE_FROM_ABI __iterator()
 199     requires default_initializable<iterator_t<_Base>>
 200   = default;
 201
 202   _LIBCPP_HIDE_FROM_ABI constexpr __iterator(_Parent& __parent, iterator_t<_Base> __current)
 203       : __parent_(std::addressof(__parent)), __current_(std::move(__current)) {}
 204
 205   // Note: `__i` should always be `__iterator<false>`, but directly using
 206   // `__iterator<false>` is ill-formed when `_Const` is false
 207   // (see http://wg21.link/class.copy.ctor#5).
 208   _LIBCPP_HIDE_FROM_ABI constexpr __iterator(__iterator<!_Const> __i)
 209     requires _Const && convertible_to<iterator_t<_View>, iterator_t<_Base>>
 210       : __parent_(__i.__parent_), __current_(std::move(__i.__current_)) {}
 211
 212   _LIBCPP_HIDE_FROM_ABI constexpr const iterator_t<_Base>& base() const& noexcept { return __current_; }
 213
 214   _LIBCPP_HIDE_FROM_ABI constexpr iterator_t<_Base> base() && { return std::move(__current_); }
 215
 216   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator*() const
 217       noexcept(noexcept(std::invoke(*__parent_->__func_, *__current_))) {
 218     return std::invoke(*__parent_->__func_, *__current_);
 219   }
 220
 221   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator++() {
 222     ++__current_;
 223     return *this;
 224   }
 225
 226   _LIBCPP_HIDE_FROM_ABI constexpr void operator++(int) { ++__current_; }
 227
 228   _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator++(int)
 229     requires forward_range<_Base>
 230   {
 231     auto __tmp = *this;
 232     ++*this;
 233     return __tmp;
 234   }
 235
 236   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator--()
 237     requires bidirectional_range<_Base>
 238   {
 239     --__current_;
 240     return *this;
 241   }
 242
 243   _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator--(int)
 244     requires bidirectional_range<_Base>
 245   {
 246     auto __tmp = *this;
 247     --*this;
 248     return __tmp;
 249   }
 250
 251   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator+=(difference_type __n)
 252     requires random_access_range<_Base>
 253   {
 254     __current_ += __n;
 255     return *this;
 256   }
 257
 258   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator-=(difference_type __n)
 259     requires random_access_range<_Base>
 260   {
 261     __current_ -= __n;
 262     return *this;
 263   }
 264
 265   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator[](difference_type __n) const
 266       noexcept(noexcept(std::invoke(*__parent_->__func_, __current_[__n])))
 267     requires random_access_range<_Base>
 268   {
 269     return std::invoke(*__parent_->__func_, __current_[__n]);
 270   }
 271
 272   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __iterator& __x, const __iterator& __y)
 273     requires equality_comparable<iterator_t<_Base>>
 274   {
 275     return __x.__current_ == __y.__current_;
 276   }
 277
 278   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<(const __iterator& __x, const __iterator& __y)
 279     requires random_access_range<_Base>
 280   {
 281     return __x.__current_ < __y.__current_;
 282   }
 283
 284   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>(const __iterator& __x, const __iterator& __y)
 285     requires random_access_range<_Base>
 286   {
 287     return __x.__current_ > __y.__current_;
 288   }
 289
 290   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<=(const __iterator& __x, const __iterator& __y)
 291     requires random_access_range<_Base>
 292   {
 293     return __x.__current_ <= __y.__current_;
 294   }
 295
 296   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>=(const __iterator& __x, const __iterator& __y)
 297     requires random_access_range<_Base>
 298   {
 299     return __x.__current_ >= __y.__current_;
 300   }
 301
 302   _LIBCPP_HIDE_FROM_ABI friend constexpr auto operator<=>(const __iterator& __x, const __iterator& __y)
 303     requires random_access_range<_Base> && three_way_comparable<iterator_t<_Base>>
 304   {
 305     return __x.__current_ <=> __y.__current_;
 306   }
 307
 308   _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator+(__iterator __i, difference_type __n)
 309     requires random_access_range<_Base>
 310   {
 311     return __iterator{*__i.__parent_, __i.__current_ + __n};
 312   }
 313
 314   _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator+(difference_type __n, __iterator __i)
 315     requires random_access_range<_Base>
 316   {
 317     return __iterator{*__i.__parent_, __i.__current_ + __n};
 318   }
 319
 320   _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator-(__iterator __i, difference_type __n)
 321     requires random_access_range<_Base>
 322   {
 323     return __iterator{*__i.__parent_, __i.__current_ - __n};
 324   }
 325
 326   _LIBCPP_HIDE_FROM_ABI friend constexpr difference_type operator-(const __iterator& __x, const __iterator& __y)
 327     requires sized_sentinel_for<iterator_t<_Base>, iterator_t<_Base>>
 328   {
 329     return __x.__current_ - __y.__current_;
 330   }
 331 };
 332
 333 #  if _LIBCPP_STD_VER >= 23
 334 template <input_range _View, move_constructible _Fn>
 335 #  else
 336 template <input_range _View, copy_constructible _Fn>
 337 #  endif
 338   requires __transform_view_constraints<_View, _Fn>
 339 template <bool _Const>
 340 class transform_view<_View, _Fn>::__sentinel {
 341   using _Parent = __maybe_const<_Const, transform_view>;
 342   using _Base   = __maybe_const<_Const, _View>;
 343
 344   sentinel_t<_Base> __end_ = sentinel_t<_Base>();
 345
 346   template <bool>
 347   friend class transform_view<_View, _Fn>::__iterator;
 348
 349   template <bool>
 350   friend class transform_view<_View, _Fn>::__sentinel;
 351
 352 public:
 353   _LIBCPP_HIDE_FROM_ABI __sentinel() = default;
 354
 355   _LIBCPP_HIDE_FROM_ABI constexpr explicit __sentinel(sentinel_t<_Base> __end) : __end_(__end) {}
 356
 357   // Note: `__i` should always be `__sentinel<false>`, but directly using
 358   // `__sentinel<false>` is ill-formed when `_Const` is false
 359   // (see http://wg21.link/class.copy.ctor#5).
 360   _LIBCPP_HIDE_FROM_ABI constexpr __sentinel(__sentinel<!_Const> __i)
 361     requires _Const && convertible_to<sentinel_t<_View>, sentinel_t<_Base>>
 362       : __end_(std::move(__i.__end_)) {}
 363
 364   _LIBCPP_HIDE_FROM_ABI constexpr sentinel_t<_Base> base() const { return __end_; }
 365
 366   template <bool _OtherConst>
 367     requires sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
 368   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __iterator<_OtherConst>& __x, const __sentinel& __y) {
 369     return __x.__current_ == __y.__end_;
 370   }
 371
 372   template <bool _OtherConst>
 373     requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
 374   _LIBCPP_HIDE_FROM_ABI friend constexpr range_difference_t<__maybe_const<_OtherConst, _View>>
 375   operator-(const __iterator<_OtherConst>& __x, const __sentinel& __y) {
 376     return __x.__current_ - __y.__end_;
 377   }
 378
 379   template <bool _OtherConst>
 380     requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
 381   _LIBCPP_HIDE_FROM_ABI friend constexpr range_difference_t<__maybe_const<_OtherConst, _View>>
 382   operator-(const __sentinel& __x, const __iterator<_OtherConst>& __y) {
 383     return __x.__end_ - __y.__current_;
 384   }
 385 };
 386
 387 namespace views {
 388 namespace __transform {
 389 struct __fn {
 390   template <class _Range, class _Fn>
 391   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Fn&& __f) const
 392       noexcept(noexcept(transform_view(std::forward<_Range>(__range), std::forward<_Fn>(__f))))
 393           -> decltype(transform_view(std::forward<_Range>(__range), std::forward<_Fn>(__f))) {
 394     return transform_view(std::forward<_Range>(__range), std::forward<_Fn>(__f));
 395   }
 396
 397   template <class _Fn>
 398     requires constructible_from<decay_t<_Fn>, _Fn>
 399   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Fn&& __f) const
 400       noexcept(is_nothrow_constructible_v<decay_t<_Fn>, _Fn>) {
 401     return __pipeable(std::__bind_back(*this, std::forward<_Fn>(__f)));
 402   }
 403 };
 404 } // namespace __transform
 405
 406 inline namespace __cpo {
 407 inline constexpr auto transform = __transform::__fn{};
 408 } // namespace __cpo
 409 } // namespace views
 410
 411 } // namespace ranges
 412
 413 #endif // _LIBCPP_STD_VER >= 20
 414
 415 _LIBCPP_END_NAMESPACE_STD
 416
 417 _LIBCPP_POP_MACROS
 418
 419 #endif // _LIBCPP___RANGES_TRANSFORM_VIEW_H