Data.Functor.Deriving

Exports functions to mechanically derive Functor instances.

For more info on how deriving Functor works, see this GHC wiki page.

Functor

deriveFunctor :: Name -> Q [Dec]

Generates a Functor instance declaration for the given data type or data family instance.

makeFmap :: Name -> Q Exp

Generates a lambda expression which behaves like fmap (without requiring a Functor instance).

deriveFunctor limitations

Be aware of the following potential gotchas:

• Type variables of kind * -> * are assumed to have Functor constraints. If this is not desirable, use makeFmap.