libcxx/include/__cxx03/__algorithm/ranges_reverse.h

   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 <__cxx03/__config>
  13 #include <__cxx03/__iterator/concepts.h>
  14 #include <__cxx03/__iterator/iter_swap.h>
  15 #include <__cxx03/__iterator/next.h>
  16 #include <__cxx03/__iterator/permutable.h>
  17 #include <__cxx03/__ranges/access.h>
  18 #include <__cxx03/__ranges/concepts.h>
  19 #include <__cxx03/__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 >= 20
  26
  27 _LIBCPP_BEGIN_NAMESPACE_STD
  28
  29 namespace ranges {
  30 namespace __reverse {
  31 struct __fn {
  32   template <bidirectional_iterator _Iter, sentinel_for<_Iter> _Sent>
  33     requires permutable<_Iter>
  34   _LIBCPP_HIDE_FROM_ABI constexpr _Iter operator()(_Iter __first, _Sent __last) const {
  35     if constexpr (random_access_iterator<_Iter>) {
  36       if (__first == __last)
  37         return __first;
  38
  39       auto __end = ranges::next(__first, __last);
  40       auto __ret = __end;
  41
  42       while (__first < --__end) {
  43         ranges::iter_swap(__first, __end);
  44         ++__first;
  45       }
  46       return __ret;
  47     } else {
  48       auto __end = ranges::next(__first, __last);
  49       auto __ret = __end;
  50
  51       while (__first != __end) {
  52         if (__first == --__end)
  53           break;
  54
  55         ranges::iter_swap(__first, __end);
  56         ++__first;
  57       }
  58       return __ret;
  59     }
  60   }
  61
  62   template <bidirectional_range _Range>
  63     requires permutable<iterator_t<_Range>>
  64   _LIBCPP_HIDE_FROM_ABI constexpr borrowed_iterator_t<_Range> operator()(_Range&& __range) const {
  65     return (*this)(ranges::begin(__range), ranges::end(__range));
  66   }
  67 };
  68 } // namespace __reverse
  69
  70 inline namespace __cpo {
  71 inline constexpr auto reverse = __reverse::__fn{};
  72 } // namespace __cpo
  73 } // namespace ranges
  74
  75 _LIBCPP_END_NAMESPACE_STD
  76
  77 #endif // _LIBCPP_STD_VER >= 20
  78
  79 #endif // _LIBCPP___ALGORITHM_RANGES_REVERSE_H