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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 <__assert>
#include <__config>
#include <__iterator/advance.h>
#include <__iterator/concepts.h>
#include <__iterator/incrementable_traits.h>
#include <__iterator/iterator_traits.h>
#include <type_traits>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
template <class _InputIter>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
typename enable_if<__is_cpp17_input_iterator<_InputIter>::value, _InputIter>::type
prev(_InputIter __x, typename iterator_traits<_InputIter>::difference_type __n = 1) {
_LIBCPP_ASSERT(__n <= 0 || __is_cpp17_bidirectional_iterator<_InputIter>::value,
"Attempt to prev(it, n) with a positive n on a non-bidirectional iterator");
_VSTD::advance(__x, -__n);
return __x;
}
#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
// [range.iter.op.prev]
namespace ranges {
namespace __prev {
struct __fn {
template <bidirectional_iterator _Ip>
_LIBCPP_HIDE_FROM_ABI
constexpr _Ip operator()(_Ip __x) const {
--__x;
return __x;
}
template <bidirectional_iterator _Ip>
_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>
_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;
}
};
} // namespace __prev
inline namespace __cpo {
inline constexpr auto prev = __prev::__fn{};
} // namespace __cpo
} // namespace ranges
#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___ITERATOR_PREV_H
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