32 Thread support library [thread]

32.6 Futures [futures]

32.6.10 Class template packaged_­task [futures.task]

32.6.10.2 Globals [futures.task.nonmembers]

template<class R, class... ArgTypes> void swap(packaged_task<R(ArgTypes...)>& x, packaged_task<R(ArgTypes...)>& y) noexcept;
Effects: As if by x.swap(y).