Using Haddock markup with Literate Haskell commenting style doesn't 
currently work.  For instance, to get Haddock markup in an lhs file:

comments
comments

> code

comments

you'd need to write:

> -- | comments
> -- comments

> code

> -- | comments

This clearly defeats the purpose of Literate Haskell.  BirdPP is
a preprocessor that works with GHC so you can write what you want:


| comments
comments

> code

| comments

Compilation of this package will give you an executable called
bunlit.  This can be used by ghc using the option -pgmL BirdPP.
E.g.

ghc -pgmL BirdPP --make Main.lhs