[Haskell-cafe] Which generic zipper?

It's sometimes difficult to figure out a good choice when you're searching for a new feature/library (when you go beyond safety of the HP). I'm looking for a generic zipper to (hopefully) navigate over an AST… so a hetrogeneous structure. It's probably sufficient to make this traversable in a fixed way, but a zipper seemed like a good idea. Google says there are lots of options (various papers and their related implementations etc). I see a generic zipper in an 'syz' package that is based on generics, which looks like a nice choice as it's now easy to add the extension for deriving generics on ADTs. However, that package looks pretty old and unmaintained. Does anyone have any suggestions/advice? Cheers -- Luke