[Haskell-beginners] help with error

[Tyler Hayes]

I'm getting an error and I do not know why...

This is what I have:


class Finite a where
  elements' :: [a]

instance (Finite a, Show a, Show b) => Show (a -> b) where
   show f = concat (map show [ a | a <- elements'::[a] ])


and this is what ghci gives me:


    Could not deduce (Finite a1) from the context ()
      arising from a use of `elements'' at Hw06.lhs:119:42-50
    Possible fix:
      add (Finite a1) to the context of an expression type signature
    In the expression: elements' :: [a]
    In a stmt of a list comprehension: a <- elements' :: [a]
    In the second argument of `map', namely
        `[a | a <- elements' :: [a]]'


What's going on here?

Thanks for the help!
- Tyler