[Haskell-beginners] Package Documentation (Haddock)

Hi, I found the Haddock documentation to the packages that came with the Haskell Platform locally on my machine. 1) It's a little bit uncomfortable to always pick the right one by hand. Is there a more comfortable way like doing e.g. 'haddock Data.List' (that's not working) to direct to the documentation of a certain module? 2) I cannot find the documentation to the packages I post installed with cabal. I tried to build them using e.g. 'cabal haddock Yampa' but that's not working. How do I do it right? Thanks for your help in advance, Bastian