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/is_nothrow_constructible.h>
  38 #include <__type_traits/is_object.h>
  39 #include <__type_traits/is_reference.h>
  40 #include <__type_traits/maybe_const.h>
  41 #include <__type_traits/remove_cvref.h>
  42 #include <__utility/forward.h>
  43 #include <__utility/in_place.h>
  44 #include <__utility/move.h>
  45
  46 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  47 #  pragma GCC system_header
  48 #endif
  49
  50 _LIBCPP_BEGIN_NAMESPACE_STD
  51
  52 #if _LIBCPP_STD_VER >= 20
  53
  54 namespace ranges {
  55
  56 template<class _Fn, class _View>
  57 concept __regular_invocable_with_range_ref =
  58   regular_invocable<_Fn, range_reference_t<_View>>;
  59
  60 template<class _View, class _Fn>
  61 concept __transform_view_constraints =
  62   view<_View> && is_object_v<_Fn> &&
  63   regular_invocable<_Fn&, range_reference_t<_View>> &&
  64   __can_reference<invoke_result_t<_Fn&, range_reference_t<_View>>>;
  65
  66 #  if _LIBCPP_STD_VER >= 23
  67 template <input_range _View, move_constructible _Fn>
  68 #  else
  69 template <input_range _View, copy_constructible _Fn>
  70 #  endif
  71   requires __transform_view_constraints<_View, _Fn>
  72 class transform_view : public view_interface<transform_view<_View, _Fn>> {
  73   template<bool> class __iterator;
  74   template<bool> class __sentinel;
  75
  76   _LIBCPP_NO_UNIQUE_ADDRESS __movable_box<_Fn> __func_;
  77   _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
  78
  79 public:
  80   _LIBCPP_HIDE_FROM_ABI
  81   transform_view()
  82     requires default_initializable<_View> && default_initializable<_Fn> = default;
  83
  84   _LIBCPP_HIDE_FROM_ABI
  85   constexpr _LIBCPP_EXPLICIT_SINCE_CXX23 transform_view(_View __base, _Fn __func)
  86     : __func_(std::in_place, std::move(__func)), __base_(std::move(__base)) {}
  87
  88   _LIBCPP_HIDE_FROM_ABI
  89   constexpr _View base() const& requires copy_constructible<_View> { return __base_; }
  90   _LIBCPP_HIDE_FROM_ABI
  91   constexpr _View base() && { return std::move(__base_); }
  92
  93   _LIBCPP_HIDE_FROM_ABI
  94   constexpr __iterator<false> begin() {
  95     return __iterator<false>{*this, ranges::begin(__base_)};
  96   }
  97   _LIBCPP_HIDE_FROM_ABI
  98   constexpr __iterator<true> begin() const
  99     requires range<const _View> &&
 100              __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
 106   constexpr __sentinel<false> end() {
 107     return __sentinel<false>(ranges::end(__base_));
 108   }
 109   _LIBCPP_HIDE_FROM_ABI
 110   constexpr __iterator<false> end()
 111     requires common_range<_View>
 112   {
 113     return __iterator<false>(*this, ranges::end(__base_));
 114   }
 115   _LIBCPP_HIDE_FROM_ABI
 116   constexpr __sentinel<true> end() const
 117     requires range<const _View> &&
 118              __regular_invocable_with_range_ref<const _Fn&, const _View>
 119   {
 120     return __sentinel<true>(ranges::end(__base_));
 121   }
 122   _LIBCPP_HIDE_FROM_ABI
 123   constexpr __iterator<true> end() const
 124     requires common_range<const _View> &&
 125              __regular_invocable_with_range_ref<const _Fn&, const _View>
 126   {
 127     return __iterator<true>(*this, ranges::end(__base_));
 128   }
 129
 130   _LIBCPP_HIDE_FROM_ABI
 131   constexpr auto size() requires sized_range<_View> { return ranges::size(__base_); }
 132   _LIBCPP_HIDE_FROM_ABI
 133   constexpr auto size() const requires sized_range<const _View> { return ranges::size(__base_); }
 134 };
 135
 136 template<class _Range, class _Fn>
 137 transform_view(_Range&&, _Fn) -> transform_view<views::all_t<_Range>, _Fn>;
 138
 139 template<class _View>
 140 struct __transform_view_iterator_concept { using type = input_iterator_tag; };
 141
 142 template<random_access_range _View>
 143 struct __transform_view_iterator_concept<_View> { using type = random_access_iterator_tag; };
 144
 145 template<bidirectional_range _View>
 146 struct __transform_view_iterator_concept<_View> { using type = bidirectional_iterator_tag; };
 147
 148 template<forward_range _View>
 149 struct __transform_view_iterator_concept<_View> { using type = forward_iterator_tag; };
 150
 151 template<class, class>
 152 struct __transform_view_iterator_category_base {};
 153
 154 template<forward_range _View, class _Fn>
 155 struct __transform_view_iterator_category_base<_View, _Fn> {
 156   using _Cat = typename iterator_traits<iterator_t<_View>>::iterator_category;
 157
 158   using iterator_category = conditional_t<
 159     is_reference_v<invoke_result_t<_Fn&, range_reference_t<_View>>>,
 160     conditional_t<
 161       derived_from<_Cat, contiguous_iterator_tag>,
 162       random_access_iterator_tag,
 163       _Cat
 164     >,
 165     input_iterator_tag
 166   >;
 167 };
 168
 169 #  if _LIBCPP_STD_VER >= 23
 170 template <input_range _View, move_constructible _Fn>
 171 #  else
 172 template <input_range _View, copy_constructible _Fn>
 173 #  endif
 174   requires __transform_view_constraints<_View, _Fn>
 175 template <bool _Const>
 176 class transform_view<_View, _Fn>::__iterator : public __transform_view_iterator_category_base<_View, _Fn> {
 177
 178   using _Parent = __maybe_const<_Const, transform_view>;
 179   using _Base = __maybe_const<_Const, _View>;
 180
 181   _Parent *__parent_ = nullptr;
 182
 183   template<bool>
 184   friend class transform_view<_View, _Fn>::__iterator;
 185
 186   template<bool>
 187   friend class transform_view<_View, _Fn>::__sentinel;
 188
 189 public:
 190   iterator_t<_Base> __current_ = iterator_t<_Base>();
 191
 192   using iterator_concept = typename __transform_view_iterator_concept<_View>::type;
 193   using value_type = remove_cvref_t<invoke_result_t<_Fn&, range_reference_t<_Base>>>;
 194   using difference_type = range_difference_t<_Base>;
 195
 196   _LIBCPP_HIDE_FROM_ABI
 197   __iterator() requires default_initializable<iterator_t<_Base>> = default;
 198
 199   _LIBCPP_HIDE_FROM_ABI
 200   constexpr __iterator(_Parent& __parent, iterator_t<_Base> __current)
 201     : __parent_(std::addressof(__parent)), __current_(std::move(__current)) {}
 202
 203   // Note: `__i` should always be `__iterator<false>`, but directly using
 204   // `__iterator<false>` is ill-formed when `_Const` is false
 205   // (see http://wg21.link/class.copy.ctor#5).
 206   _LIBCPP_HIDE_FROM_ABI
 207   constexpr __iterator(__iterator<!_Const> __i)
 208     requires _Const && convertible_to<iterator_t<_View>, iterator_t<_Base>>
 209     : __parent_(__i.__parent_), __current_(std::move(__i.__current_)) {}
 210
 211   _LIBCPP_HIDE_FROM_ABI
 212   constexpr const iterator_t<_Base>& base() const& noexcept {
 213     return __current_;
 214   }
 215
 216   _LIBCPP_HIDE_FROM_ABI
 217   constexpr iterator_t<_Base> base() && {
 218     return std::move(__current_);
 219   }
 220
 221   _LIBCPP_HIDE_FROM_ABI
 222   constexpr decltype(auto) operator*() const
 223     noexcept(noexcept(std::invoke(*__parent_->__func_, *__current_)))
 224   {
 225     return std::invoke(*__parent_->__func_, *__current_);
 226   }
 227
 228   _LIBCPP_HIDE_FROM_ABI
 229   constexpr __iterator& operator++() {
 230     ++__current_;
 231     return *this;
 232   }
 233
 234   _LIBCPP_HIDE_FROM_ABI
 235   constexpr void operator++(int) { ++__current_; }
 236
 237   _LIBCPP_HIDE_FROM_ABI
 238   constexpr __iterator operator++(int)
 239     requires forward_range<_Base>
 240   {
 241     auto __tmp = *this;
 242     ++*this;
 243     return __tmp;
 244   }
 245
 246   _LIBCPP_HIDE_FROM_ABI
 247   constexpr __iterator& operator--()
 248     requires bidirectional_range<_Base>
 249   {
 250     --__current_;
 251     return *this;
 252   }
 253
 254   _LIBCPP_HIDE_FROM_ABI
 255   constexpr __iterator operator--(int)
 256     requires bidirectional_range<_Base>
 257   {
 258     auto __tmp = *this;
 259     --*this;
 260     return __tmp;
 261   }
 262
 263   _LIBCPP_HIDE_FROM_ABI
 264   constexpr __iterator& operator+=(difference_type __n)
 265     requires random_access_range<_Base>
 266   {
 267     __current_ += __n;
 268     return *this;
 269   }
 270
 271   _LIBCPP_HIDE_FROM_ABI
 272   constexpr __iterator& operator-=(difference_type __n)
 273     requires random_access_range<_Base>
 274   {
 275     __current_ -= __n;
 276     return *this;
 277   }
 278
 279   _LIBCPP_HIDE_FROM_ABI
 280   constexpr decltype(auto) operator[](difference_type __n) const
 281     noexcept(noexcept(std::invoke(*__parent_->__func_, __current_[__n])))
 282     requires random_access_range<_Base>
 283   {
 284     return std::invoke(*__parent_->__func_, __current_[__n]);
 285   }
 286
 287   _LIBCPP_HIDE_FROM_ABI
 288   friend constexpr bool operator==(const __iterator& __x, const __iterator& __y)
 289     requires equality_comparable<iterator_t<_Base>>
 290   {
 291     return __x.__current_ == __y.__current_;
 292   }
 293
 294   _LIBCPP_HIDE_FROM_ABI
 295   friend constexpr bool operator<(const __iterator& __x, const __iterator& __y)
 296     requires random_access_range<_Base>
 297   {
 298     return __x.__current_ < __y.__current_;
 299   }
 300
 301   _LIBCPP_HIDE_FROM_ABI
 302   friend constexpr bool operator>(const __iterator& __x, const __iterator& __y)
 303     requires random_access_range<_Base>
 304   {
 305     return __x.__current_ > __y.__current_;
 306   }
 307
 308   _LIBCPP_HIDE_FROM_ABI
 309   friend constexpr bool operator<=(const __iterator& __x, const __iterator& __y)
 310     requires random_access_range<_Base>
 311   {
 312     return __x.__current_ <= __y.__current_;
 313   }
 314
 315   _LIBCPP_HIDE_FROM_ABI
 316   friend constexpr bool operator>=(const __iterator& __x, const __iterator& __y)
 317     requires random_access_range<_Base>
 318   {
 319     return __x.__current_ >= __y.__current_;
 320   }
 321
 322   _LIBCPP_HIDE_FROM_ABI
 323   friend constexpr auto operator<=>(const __iterator& __x, const __iterator& __y)
 324     requires random_access_range<_Base> && three_way_comparable<iterator_t<_Base>>
 325   {
 326     return __x.__current_ <=> __y.__current_;
 327   }
 328
 329   _LIBCPP_HIDE_FROM_ABI
 330   friend constexpr __iterator operator+(__iterator __i, difference_type __n)
 331     requires random_access_range<_Base>
 332   {
 333     return __iterator{*__i.__parent_, __i.__current_ + __n};
 334   }
 335
 336   _LIBCPP_HIDE_FROM_ABI
 337   friend constexpr __iterator operator+(difference_type __n, __iterator __i)
 338     requires random_access_range<_Base>
 339   {
 340     return __iterator{*__i.__parent_, __i.__current_ + __n};
 341   }
 342
 343   _LIBCPP_HIDE_FROM_ABI
 344   friend constexpr __iterator operator-(__iterator __i, difference_type __n)
 345     requires random_access_range<_Base>
 346   {
 347     return __iterator{*__i.__parent_, __i.__current_ - __n};
 348   }
 349
 350   _LIBCPP_HIDE_FROM_ABI
 351   friend constexpr difference_type operator-(const __iterator& __x, const __iterator& __y)
 352     requires sized_sentinel_for<iterator_t<_Base>, iterator_t<_Base>>
 353   {
 354     return __x.__current_ - __y.__current_;
 355   }
 356
 357   _LIBCPP_HIDE_FROM_ABI
 358   friend constexpr decltype(auto) iter_move(const __iterator& __i)
 359     noexcept(noexcept(*__i))
 360   {
 361     if constexpr (is_lvalue_reference_v<decltype(*__i)>)
 362       return std::move(*__i);
 363     else
 364       return *__i;
 365   }
 366 };
 367
 368 #  if _LIBCPP_STD_VER >= 23
 369 template <input_range _View, move_constructible _Fn>
 370 #  else
 371 template <input_range _View, copy_constructible _Fn>
 372 #  endif
 373   requires __transform_view_constraints<_View, _Fn>
 374 template <bool _Const>
 375 class transform_view<_View, _Fn>::__sentinel {
 376   using _Parent = __maybe_const<_Const, transform_view>;
 377   using _Base = __maybe_const<_Const, _View>;
 378
 379   sentinel_t<_Base> __end_ = sentinel_t<_Base>();
 380
 381   template<bool>
 382   friend class transform_view<_View, _Fn>::__iterator;
 383
 384   template<bool>
 385   friend class transform_view<_View, _Fn>::__sentinel;
 386
 387 public:
 388   _LIBCPP_HIDE_FROM_ABI
 389   __sentinel() = default;
 390
 391   _LIBCPP_HIDE_FROM_ABI
 392   constexpr explicit __sentinel(sentinel_t<_Base> __end) : __end_(__end) {}
 393
 394   // Note: `__i` should always be `__sentinel<false>`, but directly using
 395   // `__sentinel<false>` is ill-formed when `_Const` is false
 396   // (see http://wg21.link/class.copy.ctor#5).
 397   _LIBCPP_HIDE_FROM_ABI
 398   constexpr __sentinel(__sentinel<!_Const> __i)
 399     requires _Const && convertible_to<sentinel_t<_View>, sentinel_t<_Base>>
 400     : __end_(std::move(__i.__end_)) {}
 401
 402   _LIBCPP_HIDE_FROM_ABI
 403   constexpr sentinel_t<_Base> base() const { return __end_; }
 404
 405   template<bool _OtherConst>
 406     requires sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
 407   _LIBCPP_HIDE_FROM_ABI
 408   friend constexpr bool operator==(const __iterator<_OtherConst>& __x, const __sentinel& __y) {
 409     return __x.__current_ == __y.__end_;
 410   }
 411
 412   template<bool _OtherConst>
 413     requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
 414   _LIBCPP_HIDE_FROM_ABI
 415   friend constexpr range_difference_t<__maybe_const<_OtherConst, _View>>
 416   operator-(const __iterator<_OtherConst>& __x, const __sentinel& __y) {
 417     return __x.__current_ - __y.__end_;
 418   }
 419
 420   template<bool _OtherConst>
 421     requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
 422   _LIBCPP_HIDE_FROM_ABI
 423   friend constexpr range_difference_t<__maybe_const<_OtherConst, _View>>
 424   operator-(const __sentinel& __x, const __iterator<_OtherConst>& __y) {
 425     return __x.__end_ - __y.__current_;
 426   }
 427 };
 428
 429 namespace views {
 430 namespace __transform {
 431   struct __fn {
 432     template<class _Range, class _Fn>
 433     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI
 434     constexpr auto operator()(_Range&& __range, _Fn&& __f) const
 435       noexcept(noexcept(transform_view(std::forward<_Range>(__range), std::forward<_Fn>(__f))))
 436       -> decltype(      transform_view(std::forward<_Range>(__range), std::forward<_Fn>(__f)))
 437       { return          transform_view(std::forward<_Range>(__range), std::forward<_Fn>(__f)); }
 438
 439     template<class _Fn>
 440       requires constructible_from<decay_t<_Fn>, _Fn>
 441     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI
 442     constexpr auto operator()(_Fn&& __f) const
 443       noexcept(is_nothrow_constructible_v<decay_t<_Fn>, _Fn>)
 444     { return __range_adaptor_closure_t(std::__bind_back(*this, std::forward<_Fn>(__f))); }
 445   };
 446 } // namespace __transform
 447
 448 inline namespace __cpo {
 449   inline constexpr auto transform = __transform::__fn{};
 450 } // namespace __cpo
 451 } // namespace views
 452
 453 } // namespace ranges
 454
 455 #endif // _LIBCPP_STD_VER >= 20
 456
 457 _LIBCPP_END_NAMESPACE_STD
 458
 459 #endif // _LIBCPP___RANGES_TRANSFORM_VIEW_H