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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
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___ITERATOR_PREV_H
#define _LIBCPP___ITERATOR_PREV_H
#include <__config>
#include <__iterator/advance.h>
#include <__iterator/concepts.h>
#include <__iterator/incrementable_traits.h>
#include <__iterator/iterator_traits.h>
#include <__type_traits/enable_if.h>
#include <__utility/move.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_PUSH_MACROS
#include <__undef_macros>
_LIBCPP_BEGIN_NAMESPACE_STD
template <class _InputIter, __enable_if_t<__has_input_iterator_category<_InputIter>::value, int> = 0>
[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _InputIter
prev(_InputIter __x, typename iterator_traits<_InputIter>::difference_type __n) {
std::advance(__x, -__n);
return __x;
}
// LWG 3197
// It is unclear what the implications of "BidirectionalIterator" in the standard are.
// However, calling std::prev(non-bidi-iterator) is obviously an error and we should catch it at compile time.
template <class _InputIter, __enable_if_t<__has_input_iterator_category<_InputIter>::value, int> = 0>
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _InputIter prev(_InputIter __it) {
static_assert(__has_bidirectional_iterator_category<_InputIter>::value,
"Attempt to prev(it) with a non-bidirectional iterator");
return std::prev(std::move(__it), 1);
}
#if _LIBCPP_STD_VER >= 20
// [range.iter.op.prev]
namespace ranges {
struct __prev {
template <bidirectional_iterator _Ip>
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x) const {
--__x;
return __x;
}
template <bidirectional_iterator _Ip>
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n) const {
ranges::advance(__x, -__n);
return __x;
}
template <bidirectional_iterator _Ip>
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Ip
operator()(_Ip __x, iter_difference_t<_Ip> __n, _Ip __bound_iter) const {
ranges::advance(__x, -__n, __bound_iter);
return __x;
}
};
inline namespace __cpo {
inline constexpr auto prev = __prev{};
} // namespace __cpo
} // namespace ranges
#endif // _LIBCPP_STD_VER >= 20
_LIBCPP_END_NAMESPACE_STD
_LIBCPP_POP_MACROS
#endif // _LIBCPP___ITERATOR_PREV_H
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