September 2017 Update

Task/Move-to-front-algorithm/Haskell/move-to-front-algorithm.hs

@@ -1,19 +1,25 @@
-import qualified Data.List as L
-import qualified Data.Maybe as M
+import Data.List (delete, elemIndex, mapAccumL)
+
+import Data.Maybe (fromJust)
 
 table :: String
-table = ['a'..'z']
+table = ['a' .. 'z']
 
 encode :: String -> [Int]
-encode = snd . L.mapAccumL f table
-  where
-    f t s = ((s : L.delete s t), M.fromJust (L.elemIndex s t))
+encode =
+  let f t s = (s : delete s t, fromJust (elemIndex s t))
+  in snd . mapAccumL f table
 
 decode :: [Int] -> String
-decode = snd . L.mapAccumL f table
+decode = snd . mapAccumL f table
   where
-    f t i = let s = (t !! i) in ((s : L.delete s t), s)
+    f t i =
+      let s = (t !! i)
+      in (s : delete s t, s)
 
 main :: IO ()
-main = mapM_ (\s -> let t@(e, _) = (encode s, decode e) in print t)
-       ["broood", "bananaaa", "hiphophiphop"]
+main =
+  mapM_ print $
+  (,) <*> uncurry ((==) . fst) <$> -- Test that ((fst . fst) x) == snd x)
+  ((,) <*> (decode . snd) <$>
+   ((,) <*> encode <$> ["broood", "bananaaa", "hiphophiphop"]))