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//===----------------------------------------------------------------------===//
//
// 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___ALGORITHM_SHIFT_LEFT_H
#define _LIBCPP___ALGORITHM_SHIFT_LEFT_H
#include <__algorithm/move.h>
#include <__config>
#include <__iterator/iterator_traits.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
#if _LIBCPP_STD_VER >= 20
template <class _ForwardIterator>
inline _LIBCPP_HIDE_FROM_ABI constexpr
_ForwardIterator
shift_left(_ForwardIterator __first, _ForwardIterator __last,
typename iterator_traits<_ForwardIterator>::difference_type __n)
{
if (__n == 0) {
return __last;
}
_ForwardIterator __m = __first;
if constexpr (__has_random_access_iterator_category<_ForwardIterator>::value) {
if (__n >= __last - __first) {
return __first;
}
__m += __n;
} else {
for (; __n > 0; --__n) {
if (__m == __last) {
return __first;
}
++__m;
}
}
return std::move(__m, __last, __first);
}
#endif // _LIBCPP_STD_VER >= 20
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___ALGORITHM_SHIFT_LEFT_H
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