| //===----------------------------------------------------------------------===// |
| // |
| // 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> |
| #include <type_traits> |
| |
| #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) |
| #pragma GCC system_header |
| #endif |
| |
| _LIBCPP_BEGIN_NAMESPACE_STD |
| |
| #if _LIBCPP_STD_VER > 17 |
| |
| template <class _ForwardIterator> |
| inline _LIBCPP_INLINE_VISIBILITY 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 (__is_cpp17_random_access_iterator<_ForwardIterator>::value) { |
| if (__n >= __last - __first) { |
| return __first; |
| } |
| __m += __n; |
| } else { |
| for (; __n > 0; --__n) { |
| if (__m == __last) { |
| return __first; |
| } |
| ++__m; |
| } |
| } |
| return _VSTD::move(__m, __last, __first); |
| } |
| |
| #endif // _LIBCPP_STD_VER > 17 |
| |
| _LIBCPP_END_NAMESPACE_STD |
| |
| #endif // _LIBCPP___ALGORITHM_SHIFT_LEFT_H |
