v1/__algorithm/ranges_fold.h

0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===----------------------------------------------------------------------===//
0009
0010 #ifndef _LIBCPP___ALGORITHM_RANGES_FOLD_H
0011 #define _LIBCPP___ALGORITHM_RANGES_FOLD_H
0012
0013 #include <__concepts/assignable.h>
0014 #include <__concepts/constructible.h>
0015 #include <__concepts/convertible_to.h>
0016 #include <__concepts/invocable.h>
0017 #include <__concepts/movable.h>
0018 #include <__config>
0019 #include <__functional/invoke.h>
0020 #include <__functional/reference_wrapper.h>
0021 #include <__iterator/concepts.h>
0022 #include <__iterator/iterator_traits.h>
0023 #include <__iterator/next.h>
0024 #include <__ranges/access.h>
0025 #include <__ranges/concepts.h>
0026 #include <__ranges/dangling.h>
0027 #include <__type_traits/decay.h>
0028 #include <__type_traits/invoke.h>
0029 #include <__utility/forward.h>
0030 #include <__utility/move.h>
0031
0032 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0033 #  pragma GCC system_header
0034 #endif
0035
0036 _LIBCPP_PUSH_MACROS
0037 #include <__undef_macros>
0038
0039 _LIBCPP_BEGIN_NAMESPACE_STD
0040
0041 #if _LIBCPP_STD_VER >= 23
0042
0043 namespace ranges {
0044 template <class _Ip, class _Tp>
0045 struct in_value_result {
0046   _LIBCPP_NO_UNIQUE_ADDRESS _Ip in;
0047   _LIBCPP_NO_UNIQUE_ADDRESS _Tp value;
0048
0049   template <class _I2, class _T2>
0050     requires convertible_to<const _Ip&, _I2> && convertible_to<const _Tp&, _T2>
0051   _LIBCPP_HIDE_FROM_ABI constexpr operator in_value_result<_I2, _T2>() const& {
0052     return {in, value};
0053   }
0054
0055   template <class _I2, class _T2>
0056     requires convertible_to<_Ip, _I2> && convertible_to<_Tp, _T2>
0057   _LIBCPP_HIDE_FROM_ABI constexpr operator in_value_result<_I2, _T2>() && {
0058     return {std::move(in), std::move(value)};
0059   }
0060 };
0061
0062 template <class _Ip, class _Tp>
0063 using fold_left_with_iter_result = in_value_result<_Ip, _Tp>;
0064
0065 template <class _Fp, class _Tp, class _Ip, class _Rp, class _Up = decay_t<_Rp>>
0066 concept __indirectly_binary_left_foldable_impl =
0067     convertible_to<_Rp, _Up> &&                    //
0068     movable<_Tp> &&                                //
0069     movable<_Up> &&                                //
0070     convertible_to<_Tp, _Up> &&                    //
0071     invocable<_Fp&, _Up, iter_reference_t<_Ip>> && //
0072     assignable_from<_Up&, invoke_result_t<_Fp&, _Up, iter_reference_t<_Ip>>>;
0073
0074 template <class _Fp, class _Tp, class _Ip>
0075 concept __indirectly_binary_left_foldable =
0076     copy_constructible<_Fp> &&                     //
0077     invocable<_Fp&, _Tp, iter_reference_t<_Ip>> && //
0078     __indirectly_binary_left_foldable_impl<_Fp, _Tp, _Ip, invoke_result_t<_Fp&, _Tp, iter_reference_t<_Ip>>>;
0079
0080 struct __fold_left_with_iter {
0081   template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Tp, __indirectly_binary_left_foldable<_Tp, _Ip> _Fp>
0082   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static constexpr auto operator()(_Ip __first, _Sp __last, _Tp __init, _Fp __f) {
0083     using _Up = decay_t<invoke_result_t<_Fp&, _Tp, iter_reference_t<_Ip>>>;
0084
0085     if (__first == __last) {
0086       return fold_left_with_iter_result<_Ip, _Up>{std::move(__first), _Up(std::move(__init))};
0087     }
0088
0089     _Up __result = std::invoke(__f, std::move(__init), *__first);
0090     for (++__first; __first != __last; ++__first) {
0091       __result = std::invoke(__f, std::move(__result), *__first);
0092     }
0093
0094     return fold_left_with_iter_result<_Ip, _Up>{std::move(__first), std::move(__result)};
0095   }
0096
0097   template <input_range _Rp, class _Tp, __indirectly_binary_left_foldable<_Tp, iterator_t<_Rp>> _Fp>
0098   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static constexpr auto operator()(_Rp&& __r, _Tp __init, _Fp __f) {
0099     auto __result = operator()(ranges::begin(__r), ranges::end(__r), std::move(__init), std::ref(__f));
0100
0101     using _Up = decay_t<invoke_result_t<_Fp&, _Tp, range_reference_t<_Rp>>>;
0102     return fold_left_with_iter_result<borrowed_iterator_t<_Rp>, _Up>{std::move(__result.in), std::move(__result.value)};
0103   }
0104 };
0105
0106 inline constexpr auto fold_left_with_iter = __fold_left_with_iter();
0107
0108 struct __fold_left {
0109   template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Tp, __indirectly_binary_left_foldable<_Tp, _Ip> _Fp>
0110   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static constexpr auto operator()(_Ip __first, _Sp __last, _Tp __init, _Fp __f) {
0111     return fold_left_with_iter(std::move(__first), std::move(__last), std::move(__init), std::ref(__f)).value;
0112   }
0113
0114   template <input_range _Rp, class _Tp, __indirectly_binary_left_foldable<_Tp, iterator_t<_Rp>> _Fp>
0115   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static constexpr auto operator()(_Rp&& __r, _Tp __init, _Fp __f) {
0116     return fold_left_with_iter(ranges::begin(__r), ranges::end(__r), std::move(__init), std::ref(__f)).value;
0117   }
0118 };
0119
0120 inline constexpr auto fold_left = __fold_left();
0121 } // namespace ranges
0122
0123 #endif // _LIBCPP_STD_VER >= 23
0124
0125 _LIBCPP_END_NAMESPACE_STD
0126
0127 _LIBCPP_POP_MACROS
0128
0129 #endif // _LIBCPP___ALGORITHM_RANGES_FOLD_H