`swap` uses `move` to enable swapping objects that can only be moved but not copied (e.g., std::unique_ptr<T>). Note that this swap implementation is meant to b

`swap` uses `move` to enable swapping objects that can only be moved but not copied (e.g., std::unique_ptr<T>). Note that this swap implementation is meant to be generic---types may implement their own specific `swap` that performs no copies or moves whatsoever. Example: namespace NS { struct S { friend void swap(S& a, S& b) { // do something interesting here } }; } // later.. template<typename T> void f(T& a, T& b) { using std::swap; swap(a, b); // calls NS::swap(a, b) if T = NS::S }