Re: [Haskell-cafe] Re: Unwrapping newtypes

8 Sep 2010


      On 08/09/10 22:19, Kevin Jardine wrote:
...
Hi Tony,
I stared at that specific section for at least half an hour earlier
today but could not figure out how it applied in my specific case. The
only examples I have see are for deriving Num. Do you have any more
detail on how I could use that extension?
Here is an example:

{-# LANGUAGE GeneralizedNewtypeDeriving #-}

class C a where
  c :: a -> Int

data G = G

instance C G where
  c _ = 7

newtype H = H G deriving C

-- 
Tony Morris
http://tmorris.net/