I am trying to use Haddock for the first time on windows for a reasonably large project. I must be completely clueless because I seem to generate a lot of parse errors that have no reasonable explanation. In some cases it seems like Haddock is white space sensitive requiring the same indentation as my source code. If so, this is not clearly documented. However consider this example: in my matrix library I have this code snippet: ... -- | class instance Rmatrix, real only matrices instance Matrix Rmatrix where -- | tells us if its a submatrix (better to use pattern matching) issub x = case x of Rindx n -> False Rsubindx n -> True ... This generates a parse error on the line -- | class instance Rmatrix, real only matrices at the first s in class. Removing the | from the comment generates a parse error on the instance declaration even though there are no haddock comments that apply to it! The code prior to this looks something like... -- | copy one matrix into another copy :: m -> m -> m copy a b = mio $ do ka <- pushsub a ... and is part of the class declaration itself. I'm not sure why an auto-documentation tool shouldn't be a bit more forgiving vis a vis it's syntax. Maybe flag errors as warnings but keep on going. I run haddock from the command prompt via the command haddock.exe -o docs -v -h matrix.hs