I've downloaded your darcs repo, and it built fine (openSUSE 10.2 x86_64). Two remarks: * You use an internal class HostAddr and make two type synonyms an instance of it. This has 2 drawbacks: It is not H98 and Haddock complains about a missing link destination. I think one could handle things easily without a class, because all possible instances are known at compile time. * The types and values of AddrInfoFlags/NameInfoFlags are not very Haskell-like. Using data AddrInfoFlag = Passive | CanonName | NumericHost | ... and [AddrInfoFlag] instead of AddrInfoFlags is much nicer. The only cost is that a tiny marshaling function has to be written. Same for NameInfoFlags. Interfaces writte this way are more type safe and one can easily see which alternatives are possible for a given set of flags in a single place. Alas, the X11 package is not nice regarding the last item, either... :-( Cheers, S.