Construct one std::experimental::shared_future object from another,
so that both the source and the copy refer to the asynchronous result
associated with the source std::experimental::shared_future object, if any.
shared_future(shared_future const& other);
Constructs a new std::experimental::shared_future instance.
The asynchronous result associated with other
prior to the invocation of the constructor is associated with the
newly-constructed std::experimental::shared_future object
and other.
Nothing.
#include <experimental/future>