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_BEGIN_NAMESPACE_STD 36 37 #if _LIBCPP_STD_VER >= 23 38 39 namespace ranges { 40 template <class _Ip, class _Tp> 41 struct in_value_result { 42 _LIBCPP_NO_UNIQUE_ADDRESS _Ip in; 43 _LIBCPP_NO_UNIQUE_ADDRESS _Tp value; 44 45 template <class _I2, class _T2> 46 requires convertible_to<const _Ip&, _I2> && convertible_to<const _Tp&, _T2> 47 _LIBCPP_HIDE_FROM_ABI constexpr operator in_value_result<_I2, _T2>() const& { 48 return {in, value}; 49 } 50 51 template <class _I2, class _T2> 52 requires convertible_to<_Ip, _I2> && convertible_to<_Tp, _T2> 53 _LIBCPP_HIDE_FROM_ABI constexpr operator in_value_result<_I2, _T2>() && { 54 return {std::move(in), std::move(value)}; 55 } 56 }; 57 58 template <class _Ip, class _Tp> 59 using fold_left_with_iter_result = in_value_result<_Ip, _Tp>; 60 61 template <class _Fp, class _Tp, class _Ip, class _Rp, class _Up = decay_t<_Rp>> 62 concept __indirectly_binary_left_foldable_impl = 63 convertible_to<_Rp, _Up> && // 64 movable<_Tp> && // 65 movable<_Up> && // 66 convertible_to<_Tp, _Up> && // 67 invocable<_Fp&, _Up, iter_reference_t<_Ip>> && // 68 assignable_from<_Up&, invoke_result_t<_Fp&, _Up, iter_reference_t<_Ip>>>; 69 70 template <class _Fp, class _Tp, class _Ip> 71 concept __indirectly_binary_left_foldable = 72 copy_constructible<_Fp> && // 73 invocable<_Fp&, _Tp, iter_reference_t<_Ip>> && // 74 __indirectly_binary_left_foldable_impl<_Fp, _Tp, _Ip, invoke_result_t<_Fp&, _Tp, iter_reference_t<_Ip>>>; 75 76 struct __fold_left_with_iter { 77 template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Tp, __indirectly_binary_left_foldable<_Tp, _Ip> _Fp> 78 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI static constexpr auto 79 operator()(_Ip __first, _Sp __last, _Tp __init, _Fp __f) { 80 using _Up = decay_t<invoke_result_t<_Fp&, _Tp, iter_reference_t<_Ip>>>; 81 82 if (__first == __last) { 83 return fold_left_with_iter_result<_Ip, _Up>{std::move(__first), _Up(std::move(__init))}; 84 } 85 86 _Up __result = std::invoke(__f, std::move(__init), *__first); 87 for (++__first; __first != __last; ++__first) { 88 __result = std::invoke(__f, std::move(__result), *__first); 89 } 90 91 return fold_left_with_iter_result<_Ip, _Up>{std::move(__first), std::move(__result)}; 92 } 93 94 template <input_range _Rp, class _Tp, __indirectly_binary_left_foldable<_Tp, iterator_t<_Rp>> _Fp> 95 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI static constexpr auto operator()(_Rp&& __r, _Tp __init, _Fp __f) { 96 auto __result = operator()(ranges::begin(__r), ranges::end(__r), std::move(__init), std::ref(__f)); 97 98 using _Up = decay_t<invoke_result_t<_Fp&, _Tp, range_reference_t<_Rp>>>; 99 return fold_left_with_iter_result<borrowed_iterator_t<_Rp>, _Up>{std::move(__result.in), std::move(__result.value)}; 100 } 101 }; 102 103 inline constexpr auto fold_left_with_iter = __fold_left_with_iter(); 104 105 struct __fold_left { 106 template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Tp, __indirectly_binary_left_foldable<_Tp, _Ip> _Fp> 107 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI static constexpr auto 108 operator()(_Ip __first, _Sp __last, _Tp __init, _Fp __f) { 109 return fold_left_with_iter(std::move(__first), std::move(__last), std::move(__init), std::ref(__f)).value; 110 } 111 112 template <input_range _Rp, class _Tp, __indirectly_binary_left_foldable<_Tp, iterator_t<_Rp>> _Fp> 113 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI static constexpr auto operator()(_Rp&& __r, _Tp __init, _Fp __f) { 114 return fold_left_with_iter(ranges::begin(__r), ranges::end(__r), std::move(__init), std::ref(__f)).value; 115 } 116 }; 117 118 inline constexpr auto fold_left = __fold_left(); 119 } // namespace ranges 120 121 #endif // _LIBCPP_STD_VER >= 23 122 123 _LIBCPP_END_NAMESPACE_STD 124 125 #endif // _LIBCPP___ALGORITHM_FOLD_H 126