diff --git a/07/Main.hs b/07_haskell/Main.hs
similarity index 100%
rename from 07/Main.hs
rename to 07_haskell/Main.hs
diff --git a/07/Second.hs b/07_haskell/Second.hs
similarity index 69%
rename from 07/Second.hs
rename to 07_haskell/Second.hs
index c4ee758..c63f011 100644
--- a/07/Second.hs
+++ b/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