1fe6060f1SDimitry Andric // -*- C++ -*- 2fe6060f1SDimitry Andric //===----------------------------------------------------------------------===// 3fe6060f1SDimitry Andric // 4fe6060f1SDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 5fe6060f1SDimitry Andric // See https://llvm.org/LICENSE.txt for license information. 6fe6060f1SDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 7fe6060f1SDimitry Andric // 8fe6060f1SDimitry Andric //===----------------------------------------------------------------------===// 9fe6060f1SDimitry Andric 10fe6060f1SDimitry Andric #ifndef _LIBCPP___ITERATOR_PREV_H 11fe6060f1SDimitry Andric #define _LIBCPP___ITERATOR_PREV_H 12fe6060f1SDimitry Andric 1381ad6265SDimitry Andric #include <__assert> 14fe6060f1SDimitry Andric #include <__config> 15fe6060f1SDimitry Andric #include <__iterator/advance.h> 16fe6060f1SDimitry Andric #include <__iterator/concepts.h> 17fe6060f1SDimitry Andric #include <__iterator/incrementable_traits.h> 18fe6060f1SDimitry Andric #include <__iterator/iterator_traits.h> 19*bdd1243dSDimitry Andric #include <__type_traits/enable_if.h> 20fe6060f1SDimitry Andric 21fe6060f1SDimitry Andric #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 22fe6060f1SDimitry Andric # pragma GCC system_header 23fe6060f1SDimitry Andric #endif 24fe6060f1SDimitry Andric 25fe6060f1SDimitry Andric _LIBCPP_BEGIN_NAMESPACE_STD 26fe6060f1SDimitry Andric 27fe6060f1SDimitry Andric template <class _InputIter> 28*bdd1243dSDimitry Andric inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX17 29fe6060f1SDimitry Andric typename enable_if<__is_cpp17_input_iterator<_InputIter>::value, _InputIter>::type 30fe6060f1SDimitry Andric prev(_InputIter __x, typename iterator_traits<_InputIter>::difference_type __n = 1) { 31fe6060f1SDimitry Andric _LIBCPP_ASSERT(__n <= 0 || __is_cpp17_bidirectional_iterator<_InputIter>::value, 32fe6060f1SDimitry Andric "Attempt to prev(it, n) with a positive n on a non-bidirectional iterator"); 33fe6060f1SDimitry Andric _VSTD::advance(__x, -__n); 34fe6060f1SDimitry Andric return __x; 35fe6060f1SDimitry Andric } 36fe6060f1SDimitry Andric 37*bdd1243dSDimitry Andric #if _LIBCPP_STD_VER > 17 38fe6060f1SDimitry Andric 3904eeddc0SDimitry Andric // [range.iter.op.prev] 40fe6060f1SDimitry Andric 4104eeddc0SDimitry Andric namespace ranges { 4204eeddc0SDimitry Andric namespace __prev { 4304eeddc0SDimitry Andric 4404eeddc0SDimitry Andric struct __fn { 45fe6060f1SDimitry Andric template <bidirectional_iterator _Ip> 46fe6060f1SDimitry Andric _LIBCPP_HIDE_FROM_ABI 47fe6060f1SDimitry Andric constexpr _Ip operator()(_Ip __x) const { 48fe6060f1SDimitry Andric --__x; 49fe6060f1SDimitry Andric return __x; 50fe6060f1SDimitry Andric } 51fe6060f1SDimitry Andric 52fe6060f1SDimitry Andric template <bidirectional_iterator _Ip> 53fe6060f1SDimitry Andric _LIBCPP_HIDE_FROM_ABI 54fe6060f1SDimitry Andric constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n) const { 55fe6060f1SDimitry Andric ranges::advance(__x, -__n); 56fe6060f1SDimitry Andric return __x; 57fe6060f1SDimitry Andric } 58fe6060f1SDimitry Andric 59fe6060f1SDimitry Andric template <bidirectional_iterator _Ip> 6081ad6265SDimitry Andric _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n, _Ip __bound_iter) const { 6181ad6265SDimitry Andric ranges::advance(__x, -__n, __bound_iter); 62fe6060f1SDimitry Andric return __x; 63fe6060f1SDimitry Andric } 64fe6060f1SDimitry Andric }; 65fe6060f1SDimitry Andric 6604eeddc0SDimitry Andric } // namespace __prev 6704eeddc0SDimitry Andric 6804eeddc0SDimitry Andric inline namespace __cpo { 6904eeddc0SDimitry Andric inline constexpr auto prev = __prev::__fn{}; 7004eeddc0SDimitry Andric } // namespace __cpo 71fe6060f1SDimitry Andric } // namespace ranges 72fe6060f1SDimitry Andric 73*bdd1243dSDimitry Andric #endif // _LIBCPP_STD_VER > 17 74fe6060f1SDimitry Andric 75fe6060f1SDimitry Andric _LIBCPP_END_NAMESPACE_STD 76fe6060f1SDimitry Andric 77fe6060f1SDimitry Andric #endif // _LIBCPP___ITERATOR_PREV_H 78