Re: [Haskell-cafe] How to speedup generically parsing sum types?

* syb: toJSON and fromJSON from the Data.Aeson.Generic module. Uses the Data type class. .. As can be seen, in most cases the GHC Generics implementation is much faster than SYB and just as fast as TH. I'm impressed by how well GHC optimizes the code!

Not that it matters much if you're going with other tools, but your SYB code has a long linear chain of type rep comparisons, at every level of the recursive traversals. That is partially inherent in the SYB design (reducing everything to cast), but could probably be improved? Claus