Hmmm, seems like your (-+) is not lazy enough. Since pattern matching is strict by default, you have anything -+ (_|_) = (_|_) Therefore, the function, which is constantly (_|_), is a fixed point for the equation defining h. In other words, if you define h' x = undefined then you have h' x = (-+) anything (h anything) in particular, h' x = (-+) (first x) (h (rest x)) You can fix it by defining (-+) as x -+ ~(List y) = ...
data List a = List(Integer->a)
instance Show a => Show (List a) where show (List f) = "[" ++ show (f(0)) ++ concat ["," ++ show (f(toInteger i))| i<-[1..]] ++ "]"
list :: Integer -> List Integer list x = List(\z -> x+z)
(-+) :: a -> List a -> List a x -+ (List y) = List(f) where f 0 = x f k = y(k-1)
first :: List a -> a first (List f) = f 0
rest :: List a -> List a rest (List y) = List(f) where f k = y(k+1)
h :: List a -> List a h x = (-+) (first x) (h (rest x)) -------- _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe