It would be pretty neat for Haskell hacking if the Emacs Haskell mode could do the following. Imagine you have written some code like so: -- | The parse state. data S = S {-# UNPACK #-} !B.ByteString -- current chunk L.ByteString -- rest of the input {-# UNPACK #-} !Int64 -- bytes read -- | The 'Parser' monad is just a State monad carrying around the -- input ByteString. newtype Parser a = Parser { unParser :: S -> Consumed (Reply a) } -- | Match byte that fulfills predicate. satisfy :: (Word8 -> Bool) -- ^ Predicate that byte must fulfill. -> Parser Word8 -- ^ Matched byte. satisfy p = Parser $ \(S s ss pos) -> if B.null s then (if L.null ss then Empty (Error (ParseError pos)) else case L.splitAt 1 ss of (consuming,rest) -> let now = B.concat . L.toChunks $ consuming b = B.head now in if p b then Consumed $ Ok b (S (B.tail now) rest (pos + 1)) else Empty $ Error $ ParseError pos ) else let b = B.head s in if p b then Consumed $ Ok (B.head s) (S (B.tail s) ss (pos + 1)) else Empty $ Error $ ParseError pos Now you want an overview of your source file. One way would be to replace all the implementation parts with ellipses, like so: -- | The parse state. data S = S {-# UNPACK #-} !B.ByteString -- current chunk L.ByteString -- rest of the input {-# UNPACK #-} !Int64 -- bytes read -- | The 'Parser' monad is just a State monad carrying around the -- input ByteString. newtype Parser a = Parser { unParser :: S -> Consumed (Reply a) } -- | Match byte that fulfills predicate. satisfy :: (Word8 -> Bool) -- ^ Predicate that byte must fulfill. -> Parser Word8 -- ^ Matched byte. satisfy p = ... Binding a haskell-fold-source function to a key chain would enable you to get a quick overview of your module showing only the comments and type signatures. I've used the little function from http://emacs.wordpress.com/2007/01/16/quick-and-dirty-code-folding/ but it doesn't work well together with indented type signatures like in the example above. Anyone with strong Emacs-fu that knows how one could implement such a function? -- Johan