std::swap(std::basic_string)

 

C++

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Feature test macros (C++20)

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Technical specifications

Symbols index

External libraries

 

Strings library

Null-terminated strings

Byte strings

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Wide strings

Classes

basic_string

basic_string_view (C++17)

char_traits

 

std::basic_string

Member functions basic_string::basic_string basic_string::operator= basic_string::assign basic_string::get_allocator Element access basic_string::at basic_string::operator[] basic_string::front (C++11) basic_string::back (C++11) basic_string::data basic_string::c_str basic_string::operator  basic_string_view (C++17) Iterators basic_string::beginbasic_string::cbegin (C++11) basic_string::endbasic_string::cend (C++11) basic_string::rbeginbasic_string::crbegin (C++11) basic_string::rendbasic_string::crend (C++11) Capacity basic_string::empty basic_string::sizebasic_string::length basic_string::max_size basic_string::reserve basic_string::capacity basic_string::shrink_to_fit (C++11)   Operations basic_string::clear basic_string::insert basic_string::erase basic_string::push_back basic_string::pop_back (C++11) basic_string::append basic_string::operator+= basic_string::compare basic_string::starts_with (C++20)   basic_string::ends_with (C++20) basic_string::contains (C++23) basic_string::replace basic_string::substr basic_string::copy basic_string::resize basic_string::resize_and_overwrite (C++23) basic_string::swap

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Defined in header <string>
template< class CharT, class Traits, class Alloc > void swap( std::basic_string<CharT, Traits, Alloc> &lhs,            std::basic_string<CharT, Traits, Alloc> &rhs );		(until C++17)
template< class CharT, class Traits, class Alloc > void swap( std::basic_string<CharT, Traits, Alloc> &lhs,            std::basic_string<CharT, Traits, Alloc> &rhs ) noexcept(/* see below */);		(since C++17) (until C++20)
template< class CharT, class Traits, class Alloc > constexpr void     swap( std::basic_string<CharT, Traits, Alloc> &lhs,           std::basic_string<CharT, Traits, Alloc> &rhs ) noexcept(/* see below */);		(since C++20)

Specializes the std::swap algorithm for std::basic_string. Swaps the contents of lhs and rhs. Equivalent to lhs.swap(rhs).

Parameters

lhs, rhs

-

strings whose contents to swap

Return value

(none)

Complexity

Constant.

Exceptions noexcept specification:   noexcept(noexcept(lhs.swap(rhs)))

(since C++17)

Example

Run this code

#include <string>
#include <iostream>
 
int main() 
{
    std::string a = "AAAA";
    std::string b = "BBB";
 
    std::cout << "before swap" << '\n';
    std::cout << "a: " << a << '\n';
    std::cout << "b: " << b << '\n';
 
    std::swap(a,b);
 
    std::cout << "after swap" << '\n';
    std::cout << "a: " << a << '\n';
    std::cout << "b: " << b << '\n';
}

Output:

before swap
a: AAAA
b: BBB
after swap
a: BBB
b: AAAA

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 2064	C++11	non-member swap was noexcept and inconsistent with member swap	noexcept removed

See also

swap	swaps the contents (public member function)