Add Choice instance for Joker

Author: masaeedu

src/Data/Profunctor/Joker.purs

@@ -2,8 +2,10 @@ module Data.Profunctor.Joker where
 
 import Prelude
 
-import Data.Profunctor (class Profunctor)
+import Data.Either (Either(..))
 import Data.Newtype (class Newtype)
+import Data.Profunctor (class Profunctor)
+import Data.Profunctor.Choice (class Choice)
 
 -- | Makes a trivial `Profunctor` for a covariant `Functor`.
 newtype Joker f a b = Joker (f b)
@@ -21,5 +23,9 @@ instance functorJoker :: Functor f => Functor (Joker f a) where
 instance profunctorJoker :: Functor f => Profunctor (Joker f) where
   dimap f g (Joker a) = Joker (map g a)
 
+instance clownJoker :: Functor f => Choice (Joker f) where
+  left  (Joker f) = Joker $ map Left f
+  right (Joker f) = Joker $ map Right f
+
 hoistJoker :: forall f g a b. (f ~> g) -> Joker f a b -> Joker g a b
 hoistJoker f (Joker a) = Joker (f a)