Add applicative instance

Author: garyb

src/Control/Monad/Free.purs.hs

@@ -12,6 +12,10 @@ instance functorFree :: (Functor f) => Functor (Free f) where
   (<$>) f = go where
     go (Pure a)  = Pure (f a)
     go (Free fa) = Free (go <$> fa)
+    
+instance applicativeFree :: (Functor f) => Applicative (Free f) where
+  pure = return
+  (<*>) = ap
 
 instance monadFree :: (Functor f) => Monad (Free f) where
   return = Pure