1 //===----------------------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef _LIBCPP___ALGORITHM_RANGES_REVERSE_H 10 #define _LIBCPP___ALGORITHM_RANGES_REVERSE_H 11 12 #include <__config> 13 #include <__iterator/concepts.h> 14 #include <__iterator/iter_swap.h> 15 #include <__iterator/next.h> 16 #include <__iterator/permutable.h> 17 #include <__ranges/access.h> 18 #include <__ranges/concepts.h> 19 #include <__ranges/dangling.h> 20 21 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 22 # pragma GCC system_header 23 #endif 24 25 #if _LIBCPP_STD_VER > 17 26 27 _LIBCPP_BEGIN_NAMESPACE_STD 28 29 namespace ranges { 30 namespace __reverse { 31 struct __fn { 32 33 template <bidirectional_iterator _Iter, sentinel_for<_Iter> _Sent> 34 requires permutable<_Iter> 35 _LIBCPP_HIDE_FROM_ABI constexpr 36 _Iter operator()(_Iter __first, _Sent __last) const { 37 if constexpr (random_access_iterator<_Iter>) { 38 if (__first == __last) 39 return __first; 40 41 auto __end = ranges::next(__first, __last); 42 auto __ret = __end; 43 44 while (__first < --__end) { 45 ranges::iter_swap(__first, __end); 46 ++__first; 47 } 48 return __ret; 49 } else { 50 auto __end = ranges::next(__first, __last); 51 auto __ret = __end; 52 53 while (__first != __end) { 54 if (__first == --__end) 55 break; 56 57 ranges::iter_swap(__first, __end); 58 ++__first; 59 } 60 return __ret; 61 } 62 } 63 64 template <bidirectional_range _Range> 65 requires permutable<iterator_t<_Range>> 66 _LIBCPP_HIDE_FROM_ABI constexpr 67 borrowed_iterator_t<_Range> operator()(_Range&& __range) const { 68 return (*this)(ranges::begin(__range), ranges::end(__range)); 69 } 70 71 }; 72 } // namespace __reverse 73 74 inline namespace __cpo { 75 inline constexpr auto reverse = __reverse::__fn{}; 76 } // namespace __cpo 77 } // namespace ranges 78 79 _LIBCPP_END_NAMESPACE_STD 80 81 #endif // _LIBCPP_STD_VER > 17 82 83 #endif // _LIBCPP___ALGORITHM_RANGES_REVERSE_H 84