I have not been following this thread too closely, but I have looked at the various proposed implementations floating around and have a few comments. I noticed some have #ifdefs for platforms, which seems not very useful. I write not just cross-platform, but cross platform at the same time programs. i.e. a linux program which might be controlling slaves running on windows or linux, meaning it will have to deal with paths from either operating system in a common way. We should make sure all functionality is available on all systems as much as is feasable. Another common use is a program running under cygwin, where you generally want to let the user work with unix or windows style paths. We need to support paths as black boxes, what is returned from directory routines should be able to be passed back to system routines without modification or canonicalization. This will allow people to write file-chooser type apps, so even if the user visible display name of a file has been changed by charset conversion/whatnot, we can still pass the black box gotten out of the directory listing back to an open call and be assured of getting the right file. I don't think this is a good use of typeclasses mainly because I don't think we should use different types for different platforms. I would like a single abstract Path type which can represent paths from any platform or an encapsulated black box from the system. I liked the root-relative formulaton someone mentioned. data FilePath = Path Root [Relative] data Root = WindowsDrive Char | UnixRoot | CurrentDir | RootBB BlackBox data Relative = Dot | DotDot | Sub String | SubBB BlackBox type BlackBox = UArray Int Word8 note that black boxes can be used as path components as well as the entire path. Examples of where these would be used would be getting the current directory would return an opaque black box representing the whole path, while a directory listing would return relative black boxen. Or imagine implementing cp -r, you'd want to create the same file names in a different directory. just some comments... sorry for the hit-n-run. John -- John Meacham - ⑆repetae.net⑆john⑈