[libcxx] adds std::ranges::swap, std::swappable, and std::swappable_with
Implements parts of:
- P0898R3 Standard Library Concepts
- P1754 Rename concepts to standard_case for C++20, while we still can
Depends on D96742
Differential Revision: https://reviews.llvm.org/D97162
GitOrigin-RevId: c7443327930d1a045abf784615686c1226cdaade
diff --git a/include/concepts b/include/concepts
index 385ce09..4f97387 100644
--- a/include/concepts
+++ b/include/concepts
@@ -251,6 +251,89 @@
constructible_from<_Tp, const _Tp&> && convertible_to<const _Tp&, _Tp> &&
constructible_from<_Tp, const _Tp> && convertible_to<const _Tp, _Tp>;
+// [concept.swappable]
+namespace ranges::__swap {
+ // Deleted to inhibit ADL
+ template<class _Tp>
+ void swap(_Tp&, _Tp&) = delete;
+
+ template<class _Tp>
+ concept __class_or_enum = is_class_v<_Tp> || is_union_v<_Tp> || is_enum_v<_Tp>;
+
+ // [1]
+ template<class _Tp, class _Up>
+ concept __unqualified_swappable_with =
+ (__class_or_enum<remove_cvref_t<_Tp>> || __class_or_enum<remove_cvref_t<_Up>>) &&
+ requires(_Tp&& __t, _Up&& __u) {
+ swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u));
+ };
+
+ struct __fn;
+
+ template<class _Tp, class _Up, size_t _Size>
+ concept __swappable_arrays =
+ !__unqualified_swappable_with<_Tp(&)[_Size], _Up(&)[_Size]> &&
+ extent_v<_Tp> == extent_v<_Up> &&
+ requires(_Tp(& __t)[_Size], _Up(& __u)[_Size], const __fn& __swap) {
+ __swap(__t[0], __u[0]);
+ };
+
+ template<class _Tp>
+ concept __exchangeable =
+ !__unqualified_swappable_with<_Tp&, _Tp&> &&
+ move_constructible<_Tp> &&
+ assignable_from<_Tp&, _Tp>;
+
+ struct __fn {
+ // 2.1 `S` is `(void)swap(E1, E2)`* if `E1` or `E2` has class or enumeration type and...
+ // *The name `swap` is used here unqualified.
+ template<class _Tp, class _Up>
+ requires __unqualified_swappable_with<_Tp, _Up>
+ constexpr void operator()(_Tp&& __t, _Up&& __u) const
+ noexcept(noexcept(swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
+ {
+ swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u));
+ }
+
+ // 2.2 Otherwise, if `E1` and `E2` are lvalues of array types with equal extent and...
+ template<class _Tp, class _Up, size_t _Size>
+ requires __swappable_arrays<_Tp, _Up, _Size>
+ constexpr void operator()(_Tp(& __t)[_Size], _Up(& __u)[_Size]) const
+ noexcept(noexcept((*this)(*__t, *__u)))
+ {
+ // TODO(cjdb): replace with `ranges::swap_ranges`.
+ for (size_t __i = 0; __i < _Size; ++__i) {
+ (*this)(__t[__i], __u[__i]);
+ }
+ }
+
+ // 2.3 Otherwise, if `E1` and `E2` are lvalues of the same type `T` that models...
+ template<__exchangeable _Tp>
+ constexpr void operator()(_Tp& __x, _Tp& __y) const
+ noexcept(is_nothrow_move_constructible_v<_Tp> && is_nothrow_move_assignable_v<_Tp>)
+ {
+ __y = _VSTD::exchange(__x, _VSTD::move(__y));
+ }
+ };
+} // namespace ranges::__swap
+
+namespace ranges::inline __cpo {
+ inline constexpr auto swap = __swap::__fn{};
+} // namespace ranges::__cpo
+
+template<class _Tp>
+concept swappable = requires(_Tp& __a, _Tp& __b) { ranges::swap(__a, __b); };
+
+template<class _Tp, class _Up>
+concept swappable_with =
+ common_reference_with<_Tp&, _Up&> &&
+ requires(_Tp&& __t, _Up&& __u) {
+ ranges::swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Tp>(__t));
+ ranges::swap(_VSTD::forward<_Up>(__u), _VSTD::forward<_Up>(__u));
+ ranges::swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u));
+ ranges::swap(_VSTD::forward<_Up>(__u), _VSTD::forward<_Tp>(__t));
+ };
+
// [concept.booleantestable]
template<class _Tp>
concept __boolean_testable_impl = convertible_to<_Tp, bool>;