Hi haskellers, I am trying to understand why I get the following error in learning applicative style. Prelude> let estimates = [5,5,8,8,2,1,5,2] Prelude> (/) <$> Just $ foldl (+) 0 estimates <*> Just . fromIntegral $ length estimates <interactive>:54:1: Non type-variable argument in the constraint: Fractional (Maybe r) (Use FlexibleContexts to permit this) When checking that 'it' has the inferred type it :: forall a r. (Fractional (Maybe r), Num a, Num (Int -> Maybe a -> r)) => Maybe r -> Maybe r All the parts work individually. If use let and assign the parts to x and y it also works. E.g. This works let x = Just $ foldl (+) estimates Let y = Just . fromIntegral $ length estimates (/) <$> x <*> y I clearly do not understand exactly how these work. :-) Thanks for any help, -wes