just use [Window]

Main.hs

@@ -16,9 +16,6 @@
 import qualified Data.Map as Map
 import Data.Map (Map)
 
-import Data.Sequence as Seq
-import qualified Data.Foldable as Fold
-
 import Data.Bits
 
 import System.IO
@@ -44,7 +41,7 @@ main = do
             { display = dpy
             , screenWidth  = displayWidth  dpy (defaultScreen dpy)
             , screenHeight = displayHeight dpy (defaultScreen dpy)
-            , windows = Seq.empty
+            , windows      = []
             }
     return ()
 
@@ -78,7 +75,7 @@ handler :: Event -> W ()
 handler (MapRequestEvent {window = w}) = manage w
 
 handler (DestroyWindowEvent {window = w}) = do
-    modifyWindows (Seq.fromList . filter (/= w) . Fold.toList)
+    modifyWindows (filter (/= w))
     refresh
 
 handler (KeyEvent {event_type = t, state = mod, keycode = code})
@@ -96,11 +93,11 @@ handler _ = return ()
 --
 switch :: W ()
 switch = do
-    ws' <- getWindows
-    case viewl ws' of
-        EmptyL -> return ()
-        (w :< ws) -> do
-            setWindows (ws |> w)
+    ws <- getWindows
+    case ws of
+        []     -> return ()
+        (x:xs) -> do
+            setWindows (xs++[x]) -- snoc. polish this.
             refresh
 
 --
@@ -140,9 +137,9 @@ manage w = do
     trace "manage"
     d <- getDisplay
     ws <- getWindows
-    when (Fold.notElem w ws) $ do
+    when (w `notElem` ws) $ do
         trace "modifying"
-        modifyWindows (w <|)
+        modifyWindows (w :)
         io $ mapWindow d w
         refresh
 
@@ -151,10 +148,10 @@ manage w = do
 --
 refresh :: W ()
 refresh = do
-    v  <- getWindows
-    case viewl v of
-        EmptyL   -> return ()
-        (w :< _) -> do
+    ws <- getWindows
+    case ws of
+        []    -> return ()
+        (w:_) -> do
             d  <- getDisplay
             sw <- getScreenWidth
             sh <- getScreenHeight

W.hs

@@ -16,10 +16,9 @@
 
 module W where
 
-import Data.Sequence
-import Control.Monad.State
-import System.IO (hFlush, hPutStrLn, stderr)
+import System.IO
 import Graphics.X11.Xlib
+import Control.Monad.State
 
 --
 -- | WState, the window manager state.
@@ -29,9 +28,11 @@ data WState = WState
     { display       :: Display
     , screenWidth   :: !Int
     , screenHeight  :: !Int
-    , windows       :: Seq Window
+    , windows       :: Windows
     }
 
+type Windows = [Window]
+
 -- | The W monad, a StateT transformer over IO encapuslating the window
 -- manager state
 --
@@ -85,7 +86,7 @@ getDisplay          :: W Display
 getDisplay          = W (gets display)
 
 -- | Return the current windows
-getWindows          :: W (Seq Window)
+getWindows          :: W Windows
 getWindows          = W (gets windows)
 
 -- | Return the screen width
@@ -97,9 +98,9 @@ getScreenHeight     :: W Int
 getScreenHeight     = W (gets screenHeight)
 
 -- | Set the current window list
-setWindows          :: Seq Window -> W ()
+setWindows          ::Windows -> W ()
 setWindows x        = W (modify (\s -> s {windows = x}))
 
 -- | Modify the current window list
-modifyWindows       :: (Seq Window -> Seq Window) -> W ()
+modifyWindows       :: (Windows -> Windows) -> W ()
 modifyWindows f     = W (modify (\s -> s {windows = f (windows s)}))