[libcxx] adds ranges::fold_left_with_iter and ranges::fold_left #75259
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| // -*- C++ -*- | ||
| //===----------------------------------------------------------------------===// | ||
| // | ||
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. | ||
| // See https://llvm.org/LICENSE.txt for license information. | ||
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception | ||
| // | ||
| //===----------------------------------------------------------------------===// | ||
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| #ifndef _LIBCPP___ALGORITHM_FOLD_H | ||
| #define _LIBCPP___ALGORITHM_FOLD_H | ||
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| #include <__concepts/assignable.h> | ||
| #include <__concepts/convertible_to.h> | ||
| #include <__concepts/invocable.h> | ||
| #include <__concepts/movable.h> | ||
| #include <__config> | ||
| #include <__functional/invoke.h> | ||
| #include <__functional/reference_wrapper.h> | ||
| #include <__iterator/concepts.h> | ||
| #include <__iterator/iterator_traits.h> | ||
| #include <__iterator/next.h> | ||
| #include <__ranges/access.h> | ||
| #include <__ranges/concepts.h> | ||
| #include <__ranges/dangling.h> | ||
| #include <__type_traits/decay.h> | ||
| #include <__type_traits/invoke.h> | ||
| #include <__utility/forward.h> | ||
| #include <__utility/move.h> | ||
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| #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) | ||
| # pragma GCC system_header | ||
| #endif | ||
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| _LIBCPP_BEGIN_NAMESPACE_STD | ||
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| #if _LIBCPP_STD_VER >= 23 | ||
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| namespace ranges { | ||
| template <class _Ip, class _Tp> | ||
| struct in_value_result { | ||
| _LIBCPP_NO_UNIQUE_ADDRESS _Ip in; | ||
| _LIBCPP_NO_UNIQUE_ADDRESS _Tp value; | ||
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| template <class _I2, class _T2> | ||
| requires convertible_to<const _Ip&, _I2> && convertible_to<const _Tp&, _T2> | ||
| _LIBCPP_HIDE_FROM_ABI constexpr operator in_value_result<_I2, _T2>() const& { | ||
| return {in, value}; | ||
| } | ||
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| template <class _I2, class _T2> | ||
| requires convertible_to<_Ip, _I2> && convertible_to<_Tp, _T2> | ||
| _LIBCPP_HIDE_FROM_ABI constexpr operator in_value_result<_I2, _T2>() && { | ||
| return {std::move(in), std::move(value)}; | ||
| } | ||
| }; | ||
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| template <class _Ip, class _Tp> | ||
| using fold_left_with_iter_result = in_value_result<_Ip, _Tp>; | ||
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| template <class _Fp, class _Tp, class _Ip, class _Rp, class _Up = decay_t<_Rp>> | ||
| concept __indirectly_binary_left_foldable_impl = | ||
| convertible_to<_Rp, _Up> && // | ||
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| movable<_Tp> && // | ||
| movable<_Up> && // | ||
| convertible_to<_Tp, _Up> && // | ||
| invocable<_Fp&, _Up, iter_reference_t<_Ip>> && // | ||
| assignable_from<_Up&, invoke_result_t<_Fp&, _Up, iter_reference_t<_Ip>>>; | ||
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| template <class _Fp, class _Tp, class _Ip> | ||
| concept __indirectly_binary_left_foldable = | ||
| copy_constructible<_Fp> && // | ||
| invocable<_Fp&, _Tp, iter_reference_t<_Ip>> && // | ||
| __indirectly_binary_left_foldable_impl<_Fp, _Tp, _Ip, invoke_result_t<_Fp&, _Tp, iter_reference_t<_Ip>>>; | ||
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| struct __fold_left_with_iter { | ||
| template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Tp, __indirectly_binary_left_foldable<_Tp, _Ip> _Fp> | ||
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| _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI static constexpr auto | ||
| operator()(_Ip __first, _Sp __last, _Tp __init, _Fp __f) { | ||
| using _Up = decay_t<invoke_result_t<_Fp&, _Tp, iter_reference_t<_Ip>>>; | ||
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| if (__first == __last) { | ||
| return fold_left_with_iter_result<_Ip, _Up>{std::move(__first), _Up(std::move(__init))}; | ||
| } | ||
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| _Up __result = std::invoke(__f, std::move(__init), *__first); | ||
| for (++__first; __first != __last; ++__first) { | ||
| __result = std::invoke(__f, std::move(__result), *__first); | ||
| } | ||
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| return fold_left_with_iter_result<_Ip, _Up>{std::move(__first), std::move(__result)}; | ||
| } | ||
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| template <input_range _Rp, class _Tp, __indirectly_binary_left_foldable<_Tp, iterator_t<_Rp>> _Fp> | ||
| _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI static constexpr auto operator()(_Rp&& __r, _Tp __init, _Fp __f) { | ||
| auto __result = operator()(ranges::begin(__r), ranges::end(__r), std::move(__init), std::ref(__f)); | ||
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| using _Up = decay_t<invoke_result_t<_Fp&, _Tp, range_reference_t<_Rp>>>; | ||
| return fold_left_with_iter_result<borrowed_iterator_t<_Rp>, _Up>{std::move(__result.in), std::move(__result.value)}; | ||
| } | ||
| }; | ||
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| inline constexpr auto fold_left_with_iter = __fold_left_with_iter(); | ||
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| struct __fold_left { | ||
| template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Tp, __indirectly_binary_left_foldable<_Tp, _Ip> _Fp> | ||
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There was a problem hiding this comment. Nit: we usually use longer names for template arguments in ranges ( There was a problem hiding this comment. There's also code that uses There was a problem hiding this comment. IIUC, we did have that discussion at the time, and I think There was a problem hiding this comment. @var-const I would be happy to review any proposal put forward for a standard naming convention in libc++. Different parts do things differently, and this is very much inline with existing code in libc++. I don't think its appropriate to block this change on the broader conversation about names. There was a problem hiding this comment. @EricWF This discussion has already happened, and I can confirm that the outcome of it was to use There was a problem hiding this comment. @var-const Sounds good! That conversation already happened, there was consensus, and now there is no longer. I would be happy to help re-establish consensus in a more inclusive forum. There was a problem hiding this comment. I am okay with the current resolution given that a discussion has happened, and am happy to make a dedicated migration patch for all I think that the contribution guidelines should probably issue guidance on what kinds of names we expect, especially when it comes to names that we want to have some element of consistency for. Perhaps that could be the subject of the new discussion. There was a problem hiding this comment. See #76540 for the renaming patch. |
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| _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI static constexpr auto | ||
| operator()(_Ip __first, _Sp __last, _Tp __init, _Fp __f) { | ||
| return fold_left_with_iter(std::move(__first), std::move(__last), std::move(__init), std::ref(__f)).value; | ||
| } | ||
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| template <input_range _Rp, class _Tp, __indirectly_binary_left_foldable<_Tp, iterator_t<_Rp>> _Fp> | ||
| _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI static constexpr auto operator()(_Rp&& __r, _Tp __init, _Fp __f) { | ||
| return fold_left_with_iter(ranges::begin(__r), ranges::end(__r), std::move(__init), std::ref(__f)).value; | ||
| } | ||
| }; | ||
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| inline constexpr auto fold_left = __fold_left(); | ||
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| } // namespace ranges | ||
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| #endif // _LIBCPP_STD_VER >= 23 | ||
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| _LIBCPP_END_NAMESPACE_STD | ||
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| #endif // _LIBCPP___ALGORITHM_FOLD_H | ||
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