332da1c283
This has been broken out of D104170 since it should be merged whether or not we go ahead with the module map changes. Differential Revision: https://reviews.llvm.org/D104175
76 lines
2.2 KiB
C++
76 lines
2.2 KiB
C++
// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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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___ITERATOR_PREV_H
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#define _LIBCPP___ITERATOR_PREV_H
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#include <__config>
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#include <__debug>
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#include <__function_like.h>
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#include <__iterator/advance.h>
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#include <__iterator/concepts.h>
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#include <__iterator/incrementable_traits.h>
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#include <__iterator/iterator_traits.h>
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#include <type_traits>
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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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template <class _InputIter>
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inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
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typename enable_if<__is_cpp17_input_iterator<_InputIter>::value, _InputIter>::type
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prev(_InputIter __x, typename iterator_traits<_InputIter>::difference_type __n = 1) {
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_LIBCPP_ASSERT(__n <= 0 || __is_cpp17_bidirectional_iterator<_InputIter>::value,
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"Attempt to prev(it, n) with a positive n on a non-bidirectional iterator");
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_VSTD::advance(__x, -__n);
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return __x;
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}
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#if !defined(_LIBCPP_HAS_NO_RANGES)
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namespace ranges {
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struct __prev_fn final : private __function_like {
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constexpr explicit __prev_fn(__tag __x) noexcept : __function_like(__x) {}
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template <bidirectional_iterator _Ip>
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constexpr _Ip operator()(_Ip __x) const {
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--__x;
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return __x;
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}
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template <bidirectional_iterator _Ip>
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constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n) const {
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ranges::advance(__x, -__n);
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return __x;
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}
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template <bidirectional_iterator _Ip>
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constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n, _Ip __bound) const {
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ranges::advance(__x, -__n, __bound);
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return __x;
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}
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};
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inline constexpr auto prev = __prev_fn(__function_like::__tag());
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} // namespace ranges
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#endif // !defined(_LIBCPP_HAS_NO_RANGES)
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_LIBCPP_END_NAMESPACE_STD
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___ITERATOR_PREV_H
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