libcxx/include/__ranges/drop_while_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_DROP_WHILE_VIEW_H
  11 #define _LIBCPP___RANGES_DROP_WHILE_VIEW_H
  12
  13 #include <__algorithm/ranges_find_if_not.h>
  14 #include <__assert>
  15 #include <__concepts/constructible.h>
  16 #include <__config>
  17 #include <__functional/bind_back.h>
  18 #include <__functional/reference_wrapper.h>
  19 #include <__iterator/concepts.h>
  20 #include <__ranges/access.h>
  21 #include <__ranges/all.h>
  22 #include <__ranges/concepts.h>
  23 #include <__ranges/enable_borrowed_range.h>
  24 #include <__ranges/movable_box.h>
  25 #include <__ranges/non_propagating_cache.h>
  26 #include <__ranges/range_adaptor.h>
  27 #include <__ranges/view_interface.h>
  28 #include <__type_traits/conditional.h>
  29 #include <__type_traits/decay.h>
  30 #include <__type_traits/is_nothrow_constructible.h>
  31 #include <__type_traits/is_object.h>
  32 #include <__utility/forward.h>
  33 #include <__utility/in_place.h>
  34 #include <__utility/move.h>
  35
  36 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  37 #  pragma GCC system_header
  38 #endif
  39
  40 _LIBCPP_PUSH_MACROS
  41 #include <__undef_macros>
  42
  43 _LIBCPP_BEGIN_NAMESPACE_STD
  44
  45 #if _LIBCPP_STD_VER >= 20
  46
  47 namespace ranges {
  48
  49 template <view _View, class _Pred>
  50   requires input_range<_View> && is_object_v<_Pred> && indirect_unary_predicate<const _Pred, iterator_t<_View>>
  51 class _LIBCPP_ABI_LLVM18_NO_UNIQUE_ADDRESS drop_while_view : public view_interface<drop_while_view<_View, _Pred>> {
  52 public:
  53   _LIBCPP_HIDE_FROM_ABI drop_while_view()
  54     requires default_initializable<_View> && default_initializable<_Pred>
  55   = default;
  56
  57   _LIBCPP_HIDE_FROM_ABI constexpr _LIBCPP_EXPLICIT_SINCE_CXX23 drop_while_view(_View __base, _Pred __pred)
  58       : __base_(std::move(__base)), __pred_(std::in_place, std::move(__pred)) {}
  59
  60   _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
  61     requires copy_constructible<_View>
  62   {
  63     return __base_;
  64   }
  65
  66   _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
  67
  68   _LIBCPP_HIDE_FROM_ABI constexpr const _Pred& pred() const { return *__pred_; }
  69
  70   _LIBCPP_HIDE_FROM_ABI constexpr auto begin() {
  71     // Note: this duplicates a check in `optional` but provides a better error message.
  72     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
  73         __pred_.__has_value(),
  74         "drop_while_view needs to have a non-empty predicate before calling begin() -- did a previous "
  75         "assignment to this drop_while_view fail?");
  76     if constexpr (_UseCache) {
  77       if (!__cached_begin_.__has_value()) {
  78         __cached_begin_.__emplace(ranges::find_if_not(__base_, std::cref(*__pred_)));
  79       }
  80       return *__cached_begin_;
  81     } else {
  82       return ranges::find_if_not(__base_, std::cref(*__pred_));
  83     }
  84   }
  85
  86   _LIBCPP_HIDE_FROM_ABI constexpr auto end() { return ranges::end(__base_); }
  87
  88 private:
  89   _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
  90   _LIBCPP_NO_UNIQUE_ADDRESS __movable_box<_Pred> __pred_;
  91
  92   static constexpr bool _UseCache = forward_range<_View>;
  93   using _Cache                    = _If<_UseCache, __non_propagating_cache<iterator_t<_View>>, __empty_cache>;
  94   _LIBCPP_NO_UNIQUE_ADDRESS _Cache __cached_begin_ = _Cache();
  95 };
  96
  97 template <class _View, class _Pred>
  98 inline constexpr bool enable_borrowed_range<drop_while_view<_View, _Pred>> = enable_borrowed_range<_View>;
  99
 100 template <class _Range, class _Pred>
 101 drop_while_view(_Range&&, _Pred) -> drop_while_view<views::all_t<_Range>, _Pred>;
 102
 103 namespace views {
 104 namespace __drop_while {
 105
 106 struct __fn {
 107   template <class _Range, class _Pred>
 108   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Pred&& __pred) const
 109       noexcept(noexcept(/**/ drop_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))))
 110           -> decltype(/*--*/ drop_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))) {
 111     return /*-------------*/ drop_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred));
 112   }
 113
 114   template <class _Pred>
 115     requires constructible_from<decay_t<_Pred>, _Pred>
 116   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Pred&& __pred) const
 117       noexcept(is_nothrow_constructible_v<decay_t<_Pred>, _Pred>) {
 118     return __pipeable(std::__bind_back(*this, std::forward<_Pred>(__pred)));
 119   }
 120 };
 121
 122 } // namespace __drop_while
 123
 124 inline namespace __cpo {
 125 inline constexpr auto drop_while = __drop_while::__fn{};
 126 } // namespace __cpo
 127 } // namespace views
 128 } // namespace ranges
 129
 130 #endif // _LIBCPP_STD_VER >= 20
 131
 132 _LIBCPP_END_NAMESPACE_STD
 133
 134 _LIBCPP_POP_MACROS
 135
 136 #endif // _LIBCPP___RANGES_DROP_WHILE_VIEW_H