add dmenuMap function

Dmenu.hs

@@ -15,12 +15,13 @@
 module XMonadContrib.Dmenu (
                             -- * Usage
                             -- $usage
-                            dmenu, dmenuXinerama, 
+                            dmenu, dmenuXinerama, dmenuMap,
                             runProcessWithInput
                            ) where
 
 import XMonad
 import qualified StackSet as W
+import qualified Data.Map as M
 import System.Exit
 import System.Process
 import System.IO
@@ -58,3 +59,7 @@ dmenuXinerama opts = do
 
 dmenu :: [String] -> X (Maybe String)
 dmenu opts = io $ runProcessWithInput "dmenu" [] (unlines opts)
+
+dmenuMap :: M.Map String a -> X (Maybe a)
+dmenuMap selectionMap =
+  dmenu (M.keys selectionMap) >>= return . maybe Nothing (flip M.lookup selectionMap)