I've got this example from the Internet import Data.List import Data.Maybe firstFactorOf x | m == Nothing = x | otherwise = fromJust m where m =(find p [2..x-1]) p y = mod x y == 0 and this as a crude return the nth element of a list import Data.List import Data.Maybe -- myIndex :: [a] -> Int -> Maybe a myIndex [] _ = Nothing myIndex (x:xs) 0 = Just x myIndex (x:xs) n = myIndex xs (n-1) I would like the Just x in the second block to actually be fromJust x as in the first block, i.e., I want a number returned, not a Just typed object. I've tried changing Just x to fromJust x but get the error when I try to use it
myIndex [1,2,3,4,5] 3
* Non type-variable argument : in the constraint: Num (Maybe (Maybe a)) : (Use FlexibleContexts to permit this) : * When checking the inferred type : it :: forall a. Num (Maybe (Maybe a)) => Maybe a What am I missing here? Also, my type declaration seems to be wrong too, but I don't see why. LB