[string.swap]

# 27 Strings library [[strings]](./#strings)

## 27.4 String classes [[string.classes]](string.classes#string.swap)

### 27.4.3 Class template basic_string [[basic.string]](basic.string#string.swap)

#### 27.4.3.7 Modifiers [[string.modifiers]](string.modifiers#string.swap)

#### 27.4.3.7.8 basic_string​::​swap [string.swap]

[🔗](#lib:swap,basic_string)

`constexpr void swap(basic_string& s)
  noexcept(allocator_traits<Allocator>::propagate_on_container_swap::value ||
           allocator_traits<Allocator>::is_always_equal::value);
`

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L4263)

*Preconditions*: allocator_traits<Allocator>​::​propagate_on_container_swap​::​value is true orget_allocator() == s.get_allocator()[.](#1.sentence-1)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L4269)

*Postconditions*: *this contains the same sequence of characters that was in s,s contains the same sequence of characters that was in*this[.](#2.sentence-1)

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L4276)

*Throws*: Nothing[.](#3.sentence-1)

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L4280)

*Complexity*: Constant time[.](#4.sentence-1)