Hello, I'm currently going through the exercises in chapter 3 of Real World Haskell. One of the exercises challenges me to create a function which takes a list and makes a palindrome of it. I tried to solve it this way: palindrome :: [t] -> [t] palindrome xs = xs ++ (reverse xs) where reverse [] = [] reverse (x:xs) = (reverse xs) ++ x But when I try to compile this I get this error: Kapitel3.hs:14:32-33: error: … • Couldn't match type ‘t’ with ‘[t]’ ‘t’ is a rigid type variable bound by the type signature for: palindrome :: forall t. [t] -> [t] at /Users/jona/programmering/haskell/boken/Kapitel3.hs:13:15 Expected type: [[t]] Actual type: [t] • In the first argument of ‘reverse’, namely ‘xs’ In the second argument of ‘(++)’, namely ‘(reverse xs)’ In the expression: xs ++ (reverse xs) • Relevant bindings include xs :: [t] (bound at /Users/jona/programmering/haskell/boken/Kapitel3.hs:14:12) palindrome :: [t] -> [t] (bound at /Users/jona/programmering/haskell/boken/Kapitel3.hs:14:1) Compilation failed. It looks like I have used a function that want a list of lists, but I don't understand where. Also, is there some way to declare the type of my reverse-function in this case? Kind regards, Jona Ekenberg