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std:: swap (std::basic_string)

From cppreference.net
C++
Strings library
std::basic_string
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)
(constexpr since C++20)

Specializes the std::swap algorithm for std::basic_string . Swaps the contents of lhs and rhs .

Equivalent to lhs. swap ( rhs ) .

Contents

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 <iostream>
#include <string>
int main()
{
    std::string a = "AAA";
    std::string b = "BBBB";
    std::cout << "Before swap:\n"
                 "a = " << a << "\n"
                 "b = " << b << "\n\n";
    std::swap(a, b);
    std::cout << "After swap:\n"
                 "a = " << a << "\n"
                 "b = " << b << '\n';
}

Output: 

Before swap:
a = AAA
b = BBBB
After swap:
a = BBBB
b = AAA

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

swaps the contents
(public member function)