15 Dec
2010
15 Dec
'10
10:21 p.m.
On Wednesday 15 December 2010 22:59:28, Stephen Tetley wrote:
Doesn't mapBanana work if you give it this signature:
mapBanana :: (Something -> Something) -> Banana -> Banana mapBanana f (Banana b) = Banana (f b)
Possibly you are wanting a polymorphic Banana?
newtype Banana a = Banana a
mapBanana :: (a -> b) -> Banana a -> Banana b mapBanana f (Banana x) = Banana (f x)
For polymorphic bananas, instance Functor Banana where fmap f (Banana x) = Banana (f x) making it an Applicative and/or Monad might be useful too.