Rename haskell seminar

07_haskell/Second.hs

@@ -20,8 +20,15 @@ len' :: [a] -> Integer
 len' xs = helper 0 xs
 
 
-inv :: [a] -> [a]
-inv _ = _
+inv :: [a] -> [a] -> [a]
+inv acc (x:xs) = inv (x : acc) xs
+inv acc [] = acc
+
+rev :: [a] -> [a]
+rev xs = inv [] xs
+
+-- 1 : 2 : 3 : []
+-- 3 : 2 : 1 : []
 
 
 getF :: Name -> Maybe Name