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