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_BEGIN_NAMESPACE_STD
  41
  42 #if _LIBCPP_STD_VER >= 20
  43
  44 namespace ranges {
  45
  46 template <view _View, class _Pred>
  47   requires input_range<_View> && is_object_v<_Pred> && indirect_unary_predicate<const _Pred, iterator_t<_View>>
  48 class drop_while_view : public view_interface<drop_while_view<_View, _Pred>> {
  49 public:
  50   _LIBCPP_HIDE_FROM_ABI drop_while_view()
  51     requires default_initializable<_View> && default_initializable<_Pred>
  52   = default;
  53
  54   _LIBCPP_HIDE_FROM_ABI constexpr _LIBCPP_EXPLICIT_SINCE_CXX23 drop_while_view(_View __base, _Pred __pred)
  55       : __base_(std::move(__base)), __pred_(std::in_place, std::move(__pred)) {}
  56
  57   _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
  58     requires copy_constructible<_View>
  59   {
  60     return __base_;
  61   }
  62
  63   _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
  64
  65   _LIBCPP_HIDE_FROM_ABI constexpr const _Pred& pred() const { return *__pred_; }
  66
  67   _LIBCPP_HIDE_FROM_ABI constexpr auto begin() {
  68     _LIBCPP_ASSERT_UNCATEGORIZED(
  69         __pred_.__has_value(),
  70         "drop_while_view needs to have a non-empty predicate before calling begin() -- did a previous "
  71         "assignment to this drop_while_view fail?");
  72     if constexpr (_UseCache) {
  73       if (!__cached_begin_.__has_value()) {
  74         __cached_begin_.__emplace(ranges::find_if_not(__base_, std::cref(*__pred_)));
  75       }
  76       return *__cached_begin_;
  77     } else {
  78       return ranges::find_if_not(__base_, std::cref(*__pred_));
  79     }
  80   }
  81
  82   _LIBCPP_HIDE_FROM_ABI constexpr auto end() { return ranges::end(__base_); }
  83
  84 private:
  85   _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
  86   _LIBCPP_NO_UNIQUE_ADDRESS __movable_box<_Pred> __pred_;
  87
  88   static constexpr bool _UseCache = forward_range<_View>;
  89   using _Cache                    = _If<_UseCache, __non_propagating_cache<iterator_t<_View>>, __empty_cache>;
  90   _LIBCPP_NO_UNIQUE_ADDRESS _Cache __cached_begin_ = _Cache();
  91 };
  92
  93 template <class _View, class _Pred>
  94 inline constexpr bool enable_borrowed_range<drop_while_view<_View, _Pred>> = enable_borrowed_range<_View>;
  95
  96 template <class _Range, class _Pred>
  97 drop_while_view(_Range&&, _Pred) -> drop_while_view<views::all_t<_Range>, _Pred>;
  98
  99 namespace views {
 100 namespace __drop_while {
 101
 102 struct __fn {
 103   template <class _Range, class _Pred>
 104   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Pred&& __pred) const
 105       noexcept(noexcept(/**/ drop_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))))
 106           -> decltype(/*--*/ drop_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))) {
 107     return /*-------------*/ drop_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred));
 108   }
 109
 110   template <class _Pred>
 111     requires constructible_from<decay_t<_Pred>, _Pred>
 112   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Pred&& __pred) const
 113       noexcept(is_nothrow_constructible_v<decay_t<_Pred>, _Pred>) {
 114     return __range_adaptor_closure_t(std::__bind_back(*this, std::forward<_Pred>(__pred)));
 115   }
 116 };
 117
 118 } // namespace __drop_while
 119
 120 inline namespace __cpo {
 121 inline constexpr auto drop_while = __drop_while::__fn{};
 122 } // namespace __cpo
 123 } // namespace views
 124 } // namespace ranges
 125
 126 #endif // _LIBCPP_STD_VER >= 20
 127
 128 _LIBCPP_END_NAMESPACE_STD
 129
 130 #endif // _LIBCPP___RANGES_DROP_WHILE_VIEW_H