traversing method in haskell (errors included ;))

traverse.hs

{-# LANGUAGE TemplateHaskell #-}
import Test.QuickCheck
import Test.QuickCheck.All
import Data.List
import Data.List.Split

--
-- since lists are homogenous, we'll need something which can resemble
-- a tree
--
data NestedList a = Elem a | List [NestedList a] deriving Show

-- traversing
-- this little utility method takes a path and traverses the given list
-- with identifiers

traverse:: String -> NestedList [String] -> String
traverse p (List [])    = ""
traverse p (Elem x)     = x
traverse p (List x:xs)
    | x == h = traverse restpath (List xs)
    | otherwise = x
   where h = head ys
         ys = splitOn "/" p
         restpath = foldr (\x a -> x ++ a) [] (tail ys)