Haskell - Filter Last Element

Question

I want to filter the last element of a list that does not satisfy a property. An example would be

smallerOne :: a->Bool 
smallerOne x = x < 1 
         


        

Answer 1

The minimal change that will cause filterLast to compile is to use (++) instead of (:), as in:

filterLast p xs 
    | p (last xs) = filterLast p (init xs) ++ [last xs]

(Other lines remain the same.) The (:) function is specifically for putting a single extra element at the beginning of a list, which is not what you wanted to do here. For smallerOne, you may simply change the type signature in the way suggested by the error message, thus:

smallerOne :: (Num a, Ord a) => a->Bool