module test

import StdEnv, StdMaybe
import Data.Functor

:: Expr v
	= Lit Int
	| Add (Expr v) (Expr v)
	| E.e: Ext (e v) & eval e v
:: Fix f = Fix (f (Fix f))


class eval t v where
	eval :: (t v) -> Int
instance eval Expr v
where
	eval (Lit i) = i


Start = eval t

t :: Expr (Fix Expr)
t = Lit 42