std::copyable_function::swap
From cppreference.com
                    
                                        
                    < cpp | utility | functional | copyable function
                    
                                                            
                    |   void swap( copyable_function& other ) noexcept;  | 
(since C++26) | |
Exchanges the stored callable objects of *this and other.
Parameters
| other | - | function wrapper to exchange the stored callable object with | 
Return value
(none)
See also
|   swaps the contents  (public member function of std::function<R(Args...)>)  | |
  swaps the targets of two std::move_only_function objects (public member function of std::move_only_function)  |