9311996261
Implement the `ranges::shift_left` algorithm from [P2440R1](https://wg21.link/P2440R1). Closes: #134061 --------- Co-authored-by: Hui Xie <hui.xie1990@gmail.com> Co-authored-by: Louis Dionne <ldionne.2@gmail.com>
74 lines
2.2 KiB
C++
74 lines
2.2 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___ALGORITHM_RANGES_SHIFT_LEFT_H
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#define _LIBCPP___ALGORITHM_RANGES_SHIFT_LEFT_H
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#include <__algorithm/iterator_operations.h>
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#include <__algorithm/shift_left.h>
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#include <__config>
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#include <__iterator/concepts.h>
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#include <__iterator/distance.h>
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#include <__iterator/incrementable_traits.h>
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#include <__iterator/permutable.h>
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#include <__ranges/access.h>
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#include <__ranges/concepts.h>
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#include <__ranges/subrange.h>
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#include <__utility/move.h>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_PUSH_MACROS
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#include <__undef_macros>
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_LIBCPP_BEGIN_NAMESPACE_STD
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#if _LIBCPP_STD_VER >= 23
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namespace ranges {
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namespace __shift_left {
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struct __fn {
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template <permutable _Iter, sentinel_for<_Iter> _Sent>
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_LIBCPP_HIDE_FROM_ABI static constexpr subrange<_Iter>
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operator()(_Iter __first, _Sent __last, iter_difference_t<_Iter> __n) {
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auto __ret = std::__shift_left<_RangeAlgPolicy>(std::move(__first), std::move(__last), std::move(__n));
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return {std::move(__ret.first), std::move(__ret.second)};
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}
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template <forward_range _Range>
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requires permutable<iterator_t<_Range>>
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_LIBCPP_HIDE_FROM_ABI static constexpr borrowed_subrange_t<_Range>
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operator()(_Range&& __range, range_difference_t<_Range> __n) {
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if constexpr (sized_range<_Range>) {
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if (__n >= ranges::distance(__range)) {
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return {ranges::begin(__range), ranges::begin(__range)};
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}
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}
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auto __ret = std::__shift_left<_RangeAlgPolicy>(ranges::begin(__range), ranges::end(__range), std::move(__n));
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return {std::move(__ret.first), std::move(__ret.second)};
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}
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};
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} // namespace __shift_left
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inline namespace __cpo {
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inline constexpr auto shift_left = __shift_left::__fn{};
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} // namespace __cpo
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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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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___ALGORITHM_RANGES_SHIFT_LEFT_H
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