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 42 namespace ranges { 43 template <class _Ip, class _Tp> 44 struct 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 61 template <class _Ip, class _Tp> 62 using fold_left_with_iter_result = in_value_result<_Ip, _Tp>; 63 64 template <class _Fp, class _Tp, class _Ip, class _Rp, class _Up = decay_t<_Rp>> 65 concept __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 73 template <class _Fp, class _Tp, class _Ip> 74 concept __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 79 struct __fold_left_with_iter { 80 template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Tp, __indirectly_binary_left_foldable<_Tp, _Ip> _Fp> 81 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI static constexpr auto 82 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 _LIBCPP_NODISCARD_EXT _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 }; 105 106 inline constexpr auto fold_left_with_iter = __fold_left_with_iter(); 107 108 struct __fold_left { 109 template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Tp, __indirectly_binary_left_foldable<_Tp, _Ip> _Fp> 110 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI static constexpr auto 111 operator()(_Ip __first, _Sp __last, _Tp __init, _Fp __f) { 112 return fold_left_with_iter(std::move(__first), std::move(__last), std::move(__init), std::ref(__f)).value; 113 } 114 115 template <input_range _Rp, class _Tp, __indirectly_binary_left_foldable<_Tp, iterator_t<_Rp>> _Fp> 116 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI static constexpr auto operator()(_Rp&& __r, _Tp __init, _Fp __f) { 117 return fold_left_with_iter(ranges::begin(__r), ranges::end(__r), std::move(__init), std::ref(__f)).value; 118 } 119 }; 120 121 inline constexpr auto fold_left = __fold_left(); 122 } // namespace ranges 123 124 #endif // _LIBCPP_STD_VER >= 23 125 126 _LIBCPP_END_NAMESPACE_STD 127 128 _LIBCPP_POP_MACROS 129 130 #endif // _LIBCPP___ALGORITHM_FOLD_H 131