[expected.void.swap]

# 22 General utilities library [[utilities]](./#utilities)

## 22.8 Expected objects [[expected]](expected#void.swap)

### 22.8.7 Partial specialization of expected for void types [[expected.void]](expected.void#swap)

#### 22.8.7.5 Swap [expected.void.swap]

[🔗](#lib:swap,expected%3cvoid%3e)

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

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L9893)

*Constraints*: is_swappable_v<E> is true andis_move_constructible_v<E> is true[.](#1.sentence-1)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L9898)

*Effects*: See Table [73](#tab:expected.void.swap "Table 73: swap(expected&amp;) effects")[.](#2.sentence-1)

Table [73](#tab:expected.void.swap) — swap(expected&) effects [[tab:expected.void.swap]](./tab:expected.void.swap)  

| [🔗](#tab:expected.void.swap-row-1) | **this->has_value()** | **!this->has_value()** |
| --- | --- | --- |
| [🔗](#tab:expected.void.swap-row-2)<br>**rhs.has_value()** | no effects | calls rhs.swap(*this) |
| [🔗](#tab:expected.void.swap-row-3)<br>**!rhs.has_value()** | *see below* | equivalent to: using std​::​swap; swap(*unex*, rhs.*unex*); |

For the case where rhs.has_value() is false andthis->has_value() is true, equivalent to:construct_at(addressof(*unex*), std::move(rhs.*unex*));
destroy_at(addressof(rhs.*unex*));*has_val* = false;
rhs.*has_val* = true;

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L9923)

*Throws*: Any exception thrown by the expressions in the *Effects*[.](#3.sentence-1)

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L9927)

*Remarks*: The exception specification is equivalent tois_nothrow_move_constructible_v<E> && is_nothrow_swappable_v<E>[.](#4.sentence-1)

[🔗](#lib:swap,expected%3cvoid%3e_)

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

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L9939)

*Effects*: Equivalent to x.swap(y)[.](#5.sentence-1)