[Haskell-cafe] Best way to instance Fix?

[Sam Martin]

Hi!

I'm trying to work out the best way to generate (ideally derive) instances for the Fix type. Here's a cut down example:

data Greet x = AlloAllo x x | AuRevoir deriving Show
newtype Fix f = In { out :: f (Fix f) } -- deriving Show -- DOESN'T COMPILE

-- workaround
instance Show (Fix Greet) where show (In i) = "In " ++ show i

In other words, given a number of parametised types that I can derive, say, Ord, Eq and Show for, how should I go about getting the instances for the Fix-d version of them as well? I've tried a few things, but no luck so far. 

Any clues?

Cheers,
Sam
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