Deriving instances for GADTs

Eq, Ord, Show can be derived using the StandaloneDeriving extension (implicitly using the stock deriving strategy).

To derive instances for Some f (where f is your GADT), as well as DSum f g, you will need to use the following libraries :

• some and dependent-sum - for deriving GEq, GShow, GCompare
• aeson-gadt-th - for deriving JSON instances
  • Use this in conjunction with dependent-sum-aeson-orphans to get instances for ToJSON (Some f)

The kind-generics package generalizes the approach of GHC.Generics to GADTs.