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