std::swap(std::variant)

Overloads the std::swap algorithm for std::variant. Effectively calls lhs.swap(rhs)

This overload participates in overload resolution only if std::is_move_constructible_v<T_i> and std::is_swappable_v<T_i> are both true for all T_i in Types...

Parameters

Return value

(none)

Exceptions

Notes

Example

#include <iostream>
#include <string>
#include <variant>
 
void print(auto const& v, char term = '\n')
{
    std::visit([](auto&& o) { std::cout << o; }, v);
    std::cout << term;
}
 
int main()
{
    std::variant<int, std::string> v1{123}, v2{"XYZ"};
    print(v1, ' ');
    print(v2);
 
    std::swap(v1, v2);
    print(v1, ' ');
    print(v2);
 
    std::variant<double, std::string> v3{3.14};
    // std::swap(v1, v3); // ERROR: ~ inconsistent parameter packs
}

123 XYZ
XYZ 123

Defect reports

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

See also