NAME¶

swap(std::move_only_function) - swap(std::move_only_function)

Synopsis¶

friend void swap( move_only_function& lhs, move_only_function& rhs ) (since C++23)
noexcept;

Overloads the std::swap algorithm for std::move_only_function. Exchanges the state
of lhs with that of rhs. Effectively calls lhs.swap(rhs).

This function is not visible to ordinary unqualified or qualified lookup, and can
only be found by argument-dependent lookup when
std::move_only_function<FunctionType> is an associated class of the arguments.

Parameters¶

lhs, rhs - std::move_only_function objects whose states to swap

Return value¶

(none)

Example¶

// Run this code

#include <concepts>
#include <functional>
#include <iostream>

void foo(const char* str, int x)
{
std::cout << "foo(\"" << str << "\", " << x << ")\n";
}

void bar(const char* str, int x)
{
std::cout << "bar(\"" << str << "\", " << x << ")\n";
}

int main()
{
std::move_only_function<void(const char*, int) const> f1{foo};
std::move_only_function<void(const char*, int) const> f2{bar};

f1("f1", 1);
f2("f2", 2);

std::cout << "std::ranges::swap(f1, f2);\n";
std::ranges::swap(f1, f2); // finds the hidden friend

f1("f1", 1);
f2("f2", 2);
}

Output:¶

foo("f1", 1)
bar("f2", 2)
std::ranges::swap(f1, f2);
bar("f1", 1)
foo("f2", 2)

See also¶

swap swaps the targets of two std::move_only_function objects
(C++23) (public member function)
std::swap(std::function) specializes the std::swap algorithm
(C++11) (function template)