XMonad.Util.EZConfig: minor cleanups

XMonad/Util/EZConfig.hs

@@ -35,7 +35,7 @@ import XMonad.Actions.Submap
 import qualified Data.Map as M
 import Data.List (foldl', intersperse, sortBy, groupBy, nub)
 import Data.Ord (comparing)
-import Data.Maybe (catMaybes, isNothing, isJust, fromJust)
+import Data.Maybe
 import Control.Arrow (first, (&&&))
 
 import Text.ParserCombinators.ReadP
@@ -205,16 +205,14 @@ op `on` f = \x y -> f x `op` f y
 --   @(KeyMask,KeySym)@ pairs.  Key sequences which fail to parse will
 --   be ignored.
 readKeymap :: XConfig l -> [(String, X())] -> [([(KeyMask,KeySym)], X())]
-readKeymap c = catMaybes . map (maybeKeys . first (readKeySequence c))
+readKeymap c = mapMaybe (maybeKeys . first (readKeySequence c))
   where maybeKeys (Nothing,_) = Nothing
         maybeKeys (Just k, act) = Just (k, act)
 
 -- | Parse a sequence of keys, returning Nothing if there is
 --   a parse failure (no parse, or ambiguous parse).
 readKeySequence :: XConfig l -> String -> Maybe [(KeyMask, KeySym)]
-readKeySequence c s = case parses s of
-    [k] -> Just k
-    _   -> Nothing
+readKeySequence c = listToMaybe . parses
   where parses = map fst . filter (null.snd) . readP_to_S (parseKeySequence c)
 
 -- | Parse a sequence of key combinations separated by spaces, e.g.