| // -*- 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) const { |
| ranges::advance(__x, -__n, __bound); |
| 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 |