module GHC.Generics.Lens
(
generic
, generic1
, every
, GTraversal
) where
import Control.Applicative
import Control.Lens.Iso hiding (from)
import Control.Lens.Traversal
import Control.Lens.Type
import Data.Maybe (fromJust)
import Data.Typeable
import GHC.Generics
generic :: (Generic a, Generic b) => Iso a b (Rep a x) (Rep b y)
generic = isos from to from to
generic1 :: (Generic1 f, Generic1 g) => Iso (f a) (g b) (Rep1 f a) (Rep1 g b)
generic1 = isos from1 to1 from1 to1
every :: (Generic a, GTraversal (Rep a), Typeable b) => Simple Traversal a b
every = generic . everyr True
class GTraversal f where
everyr :: Typeable b => Bool -> Simple Traversal (f a) b
instance (Generic a, GTraversal (Rep a), Typeable a) => GTraversal (K1 i a) where
everyr rec f (K1 a) = case cast a `maybeArg1Of` f of
Just b -> K1 . fromJust . cast <$> f b
Nothing | rec -> K1 <$> fmap generic (everyr False) f a
| otherwise -> pure $ K1 a
where
maybeArg1Of :: Maybe c -> (c -> d) -> Maybe c
maybeArg1Of = const
instance GTraversal U1 where
everyr _ _ U1 = pure U1
instance (GTraversal f, GTraversal g) => GTraversal (f :*: g) where
everyr _ f (x :*: y) = (:*:) <$> everyr True f x <*> everyr True f y
instance (GTraversal f, GTraversal g) => GTraversal (f :+: g) where
everyr _ f (L1 x) = L1 <$> everyr True f x
everyr _ f (R1 x) = R1 <$> everyr True f x
instance GTraversal a => GTraversal (M1 i c a) where
everyr rec f (M1 x) = M1 <$> everyr rec f x
instance (Traversable f, GTraversal g) => GTraversal (f :.: g) where
everyr _ f (Comp1 fgp) = Comp1 <$> traverse (everyr True f) fgp