[Haskell-cafe] Just found GHCI can be used as a debugger

Hello, By randomly typing :<Tab> under GHCI, I discovered it could be used as a debugger (:breakpoint, :step, etc.) Three questions in that regard: 1) Is there some documentation about it? 2) I haven't investigated much, is that fairly thorough and convenient? Does some people over here use those functions on a regular basis? 3) Is it possible to save the state (notably to save the position of the breakpoints)? Thanks!