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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___ALGORITHM_RANGES_FOLD_H
11#define _LIBCPP___ALGORITHM_RANGES_FOLD_H
12
13#include <__concepts/assignable.h>
14#include <__concepts/constructible.h>
15#include <__concepts/convertible_to.h>
16#include <__concepts/invocable.h>
17#include <__concepts/movable.h>
18#include <__config>
19#include <__functional/invoke.h>
20#include <__functional/reference_wrapper.h>
21#include <__iterator/concepts.h>
22#include <__iterator/iterator_traits.h>
23#include <__iterator/next.h>
24#include <__ranges/access.h>
25#include <__ranges/concepts.h>
26#include <__ranges/dangling.h>
27#include <__type_traits/decay.h>
28#include <__type_traits/invoke.h>
29#include <__utility/forward.h>
30#include <__utility/move.h>
31
32#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
33# pragma GCC system_header
34#endif
35
36_LIBCPP_PUSH_MACROS
37#include <__undef_macros>
38
39_LIBCPP_BEGIN_NAMESPACE_STD
40
41#if _LIBCPP_STD_VER >= 23
42
43namespace ranges {
44template <class _Ip, class _Tp>
45struct in_value_result {
46 _LIBCPP_NO_UNIQUE_ADDRESS _Ip in;
47 _LIBCPP_NO_UNIQUE_ADDRESS _Tp value;
48
49 template <class _I2, class _T2>
50 requires convertible_to<const _Ip&, _I2> && convertible_to<const _Tp&, _T2>
51 _LIBCPP_HIDE_FROM_ABI constexpr operator in_value_result<_I2, _T2>() const& {
52 return {in, value};
53 }
54
55 template <class _I2, class _T2>
56 requires convertible_to<_Ip, _I2> && convertible_to<_Tp, _T2>
57 _LIBCPP_HIDE_FROM_ABI constexpr operator in_value_result<_I2, _T2>() && {
58 return {std::move(in), std::move(value)};
59 }
60};
61
62template <class _Ip, class _Tp>
63using fold_left_with_iter_result = in_value_result<_Ip, _Tp>;
64
65template <class _Fp, class _Tp, class _Ip, class _Rp, class _Up = decay_t<_Rp>>
66concept __indirectly_binary_left_foldable_impl =
67 convertible_to<_Rp, _Up> && //
68 movable<_Tp> && //
69 movable<_Up> && //
70 convertible_to<_Tp, _Up> && //
71 invocable<_Fp&, _Up, iter_reference_t<_Ip>> && //
72 assignable_from<_Up&, invoke_result_t<_Fp&, _Up, iter_reference_t<_Ip>>>;
73
74template <class _Fp, class _Tp, class _Ip>
75concept __indirectly_binary_left_foldable =
76 copy_constructible<_Fp> && //
77 invocable<_Fp&, _Tp, iter_reference_t<_Ip>> && //
78 __indirectly_binary_left_foldable_impl<_Fp, _Tp, _Ip, invoke_result_t<_Fp&, _Tp, iter_reference_t<_Ip>>>;
79
80struct __fold_left_with_iter {
81 template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Tp, __indirectly_binary_left_foldable<_Tp, _Ip> _Fp>
82 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static constexpr auto operator()(_Ip __first, _Sp __last, _Tp __init, _Fp __f) {
83 using _Up = decay_t<invoke_result_t<_Fp&, _Tp, iter_reference_t<_Ip>>>;
84
85 if (__first == __last) {
86 return fold_left_with_iter_result<_Ip, _Up>{std::move(__first), _Up(std::move(__init))};
87 }
88
89 _Up __result = std::invoke(__f, std::move(__init), *__first);
90 for (++__first; __first != __last; ++__first) {
91 __result = std::invoke(__f, std::move(__result), *__first);
92 }
93
94 return fold_left_with_iter_result<_Ip, _Up>{std::move(__first), std::move(__result)};
95 }
96
97 template <input_range _Rp, class _Tp, __indirectly_binary_left_foldable<_Tp, iterator_t<_Rp>> _Fp>
98 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static constexpr auto operator()(_Rp&& __r, _Tp __init, _Fp __f) {
99 auto __result = operator()(ranges::begin(__r), ranges::end(__r), std::move(__init), std::ref(__f));
100
101 using _Up = decay_t<invoke_result_t<_Fp&, _Tp, range_reference_t<_Rp>>>;
102 return fold_left_with_iter_result<borrowed_iterator_t<_Rp>, _Up>{std::move(__result.in), std::move(__result.value)};
103 }
104};
105
106inline constexpr auto fold_left_with_iter = __fold_left_with_iter();
107
108struct __fold_left {
109 template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Tp, __indirectly_binary_left_foldable<_Tp, _Ip> _Fp>
110 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static constexpr auto operator()(_Ip __first, _Sp __last, _Tp __init, _Fp __f) {
111 return fold_left_with_iter(std::move(__first), std::move(__last), std::move(__init), std::ref(__f)).value;
112 }
113
114 template <input_range _Rp, class _Tp, __indirectly_binary_left_foldable<_Tp, iterator_t<_Rp>> _Fp>
115 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static constexpr auto operator()(_Rp&& __r, _Tp __init, _Fp __f) {
116 return fold_left_with_iter(ranges::begin(__r), ranges::end(__r), std::move(__init), std::ref(__f)).value;
117 }
118};
119
120inline constexpr auto fold_left = __fold_left();
121} // namespace ranges
122
123#endif // _LIBCPP_STD_VER >= 23
124
125_LIBCPP_END_NAMESPACE_STD
126
127_LIBCPP_POP_MACROS
128
129#endif // _LIBCPP___ALGORITHM_RANGES_FOLD_H