title: How to use :? to find all function list and manual in ghci
body: <p>everyone, i'm pretty new to haskell. i was a c++ programmer.
  how to find a detailed list of functions in a particular module such like in the default "prelude" module? and how to find out how these functions work in ghci environment?
  ie. is there a command to find out all functions in "Prelude"?
  Thanks.</p>