#### use_future_t::operator()

Wrap a function object in a packaged task.

    template<
        typename Function>
    unspecified operator()(
        Function && f) const;

The `package` function is used to adapt a function object as a packaged task. When this adapter is passed as a completion token to an asynchronous operation, the result of the function object is retuned via a std::future.

###### Example

    std::future<std::size_t> fut =
      my_socket.async_read_some(buffer,
        use_future([](asio::error_code ec, std::size_t n)
          {
            return ec ? 0 : n;
          }));
    ...
    std::size_t n = fut.get();