something of the type t1 -> t2 -> t3 where t3 = f(t1, t2). Generalization of zip/zipWith. I have never seen that example.
Obviously a lot is missing in the above -- in particular, good names for the examples, and the test data. And the idea how to organize the files with examples and test data within our DARCS repository.
I think these are good examples. The only thing I miss is a generic variant of map :: (a->b) -> [a]->[b].
Though the generic zipWith function would already demonstrate the power of the library --- if you can do generic zipWith, you should be able to do generic map.
Yes, gzipWith can be viewed as a generalisation of map. But it is a bit more complex (with three type variables, and an occurrence of Maybe). Does gzipWith add something if you have gmap? Otherwise I prefer to take gmap. -- Johan