libcxx/include/__concepts/swappable.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___CONCEPTS_SWAPPABLE_H
  10 #define _LIBCPP___CONCEPTS_SWAPPABLE_H
  11
  12 #include <__concepts/assignable.h>
  13 #include <__concepts/class_or_enum.h>
  14 #include <__concepts/common_reference_with.h>
  15 #include <__concepts/constructible.h>
  16 #include <__config>
  17 #include <__cstddef/size_t.h>
  18 #include <__type_traits/extent.h>
  19 #include <__type_traits/is_nothrow_assignable.h>
  20 #include <__type_traits/is_nothrow_constructible.h>
  21 #include <__type_traits/remove_cvref.h>
  22 #include <__utility/exchange.h>
  23 #include <__utility/forward.h>
  24 #include <__utility/move.h>
  25 #include <__utility/swap.h>
  26
  27 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  28 #  pragma GCC system_header
  29 #endif
  30
  31 _LIBCPP_PUSH_MACROS
  32 #include <__undef_macros>
  33
  34 _LIBCPP_BEGIN_NAMESPACE_STD
  35
  36 #if _LIBCPP_STD_VER >= 20
  37
  38 // [concept.swappable]
  39
  40 namespace ranges {
  41 namespace __swap {
  42
  43 template <class _Tp>
  44 void swap(_Tp&, _Tp&) = delete;
  45
  46 // clang-format off
  47 template <class _Tp, class _Up>
  48 concept __unqualified_swappable_with =
  49     (__class_or_enum<remove_cvref_t<_Tp>> || __class_or_enum<remove_cvref_t<_Up>>) &&
  50     requires(_Tp&& __t, _Up&& __u) {
  51         swap(std::forward<_Tp>(__t), std::forward<_Up>(__u));
  52     };
  53 // clang-format on
  54
  55 struct __fn;
  56
  57 // clang-format off
  58 template <class _Tp, class _Up, size_t _Size>
  59 concept __swappable_arrays =
  60     !__unqualified_swappable_with<_Tp (&)[_Size], _Up (&)[_Size]> &&
  61     extent_v<_Tp> == extent_v<_Up> &&
  62     requires(_Tp (&__t)[_Size], _Up (&__u)[_Size], const __fn& __swap) {
  63         __swap(__t[0], __u[0]);
  64     };
  65 // clang-format on
  66
  67 template <class _Tp>
  68 concept __exchangeable =
  69     !__unqualified_swappable_with<_Tp&, _Tp&> && move_constructible<_Tp> && assignable_from<_Tp&, _Tp>;
  70
  71 struct __fn {
  72   // 2.1   `S` is `(void)swap(E1, E2)`* if `E1` or `E2` has class or enumeration type and...
  73   // *The name `swap` is used here unqualified.
  74   template <class _Tp, class _Up>
  75     requires __unqualified_swappable_with<_Tp, _Up>
  76   _LIBCPP_HIDE_FROM_ABI constexpr void operator()(_Tp&& __t, _Up&& __u) const
  77       noexcept(noexcept(swap(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) {
  78     swap(std::forward<_Tp>(__t), std::forward<_Up>(__u));
  79   }
  80
  81   // 2.2   Otherwise, if `E1` and `E2` are lvalues of array types with equal extent and...
  82   template <class _Tp, class _Up, size_t _Size>
  83     requires __swappable_arrays<_Tp, _Up, _Size>
  84   _LIBCPP_HIDE_FROM_ABI constexpr void operator()(_Tp (&__t)[_Size], _Up (&__u)[_Size]) const
  85       noexcept(noexcept((*this)(*__t, *__u))) {
  86     // TODO(cjdb): replace with `ranges::swap_ranges`.
  87     for (size_t __i = 0; __i < _Size; ++__i) {
  88       (*this)(__t[__i], __u[__i]);
  89     }
  90   }
  91
  92   // 2.3   Otherwise, if `E1` and `E2` are lvalues of the same type `T` that models...
  93   template <__exchangeable _Tp>
  94   _LIBCPP_HIDE_FROM_ABI constexpr void operator()(_Tp& __x, _Tp& __y) const
  95       noexcept(is_nothrow_move_constructible_v<_Tp> && is_nothrow_move_assignable_v<_Tp>) {
  96     __y = std::exchange(__x, std::move(__y));
  97   }
  98 };
  99 } // namespace __swap
 100
 101 inline namespace __cpo {
 102 inline constexpr auto swap = __swap::__fn{};
 103 } // namespace __cpo
 104 } // namespace ranges
 105
 106 template <class _Tp>
 107 concept swappable = requires(_Tp& __a, _Tp& __b) { ranges::swap(__a, __b); };
 108
 109 template <class _Tp, class _Up>
 110 concept swappable_with = common_reference_with<_Tp, _Up> && requires(_Tp&& __t, _Up&& __u) {
 111   ranges::swap(std::forward<_Tp>(__t), std::forward<_Tp>(__t));
 112   ranges::swap(std::forward<_Up>(__u), std::forward<_Up>(__u));
 113   ranges::swap(std::forward<_Tp>(__t), std::forward<_Up>(__u));
 114   ranges::swap(std::forward<_Up>(__u), std::forward<_Tp>(__t));
 115 };
 116
 117 #endif // _LIBCPP_STD_VER >= 20
 118
 119 _LIBCPP_END_NAMESPACE_STD
 120
 121 _LIBCPP_POP_MACROS
 122
 123 #endif // _LIBCPP___CONCEPTS_SWAPPABLE_H