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swap(std::move_only_function)

friend void swap( move_only_function& lhs, move_only_function& rhs ) noexcept;

(since C++23)

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

#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)

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

swap(std::move_only_function)

Parameters

Return value

Example

See also