[uBLAS] Constructing from std::vector

Hi, I'm starting to play with the uBLAS library. So far so good... I'd like to be able to construct a ublas::vector from a std::vector. I can't seem to find how to do this. Do I have to go through std::copy or something equivalent or is there a constructor I've missed? If it doesn't exist, is there a reason why not? Perhaps there are some holes in my understanding. Thanks, Alex