22 General utilities library [utilities]

22.8 Expected objects [expected]

22.8.6 Class template expected [expected.expected]

22.8.6.5 Swap [expected.object.swap]

constexpr void swap(expected& rhs) noexcept(see below);

Constraints:

(1.1)
is_swappable_v<T> is true and
(1.2)
is_swappable_v<E> is true and
(1.3)
is_move_constructible_v<T> && is_move_constructible_v<E> is true, and
(1.4)
is_nothrow_move_constructible_v<T> || is_nothrow_move_constructible_v<E> is true.

Effects: See Table 67 .

Table 67: swap(expected&) effects [tab:expected.object.swap]

🔗		this->has_value()	!this->has_value()
🔗	rhs.has_value()	equivalent to: using std::swap; swap(val, rhs.val);	calls rhs.swap(*this)
🔗	!rhs.has_value()	see below	equivalent to: using std::swap; swap(unex, rhs.unex);

For the case where rhs.has_value() is false and this->has_value() is true, equivalent to: if constexpr (is_nothrow_move_constructible_v<E>) { E tmp(std::move(rhs.unex)); destroy_at(addressof(rhs.unex)); try { construct_at(addressof(rhs.val), std::move(val)); destroy_at(addressof(val)); construct_at(addressof(unex), std::move(tmp)); } catch(...) { construct_at(addressof(rhs.unex), std::move(tmp)); throw; } } else { T tmp(std::move(val)); destroy_at(addressof(val)); try { construct_at(addressof(unex), std::move(rhs.unex)); destroy_at(addressof(rhs.unex)); construct_at(addressof(rhs.val), std::move(tmp)); } catch (...) { construct_at(addressof(val), std::move(tmp)); throw; } } has_val = false; rhs.has_val = true;

Throws: Any exception thrown by the expressions in the Effects.

Remarks: The exception specification is equivalent to: is_nothrow_move_constructible_v<T> && is_nothrow_swappable_v<T> && is_nothrow_move_constructible_v<E> && is_nothrow_swappable_v<E>

🔗

friend constexpr void swap(expected& x, expected& y) noexcept(noexcept(x.swap(y)));

Effects: Equivalent to x.swap(y).