specifying main on command line

This was in response to a post I made and I would really really like to see something like this in ghc (I don't particularly care if f is IO a or IO (), though).

Ack! This kind of change would be good, but it doesn't go quite far enough. In my opinion, you should be able to specify --main=M.f, where M is any module and f is anything of type IO a for some a.