Avoid using return (), use void and forM_

6 files changed, 28 insertions, 41 deletions

diff --git a/Bustle/Renderer.hs b/Bustle/Renderer.hs
index 36dd580..a962817 100644
--- a/Bustle/Renderer.hs
+++ b/Bustle/Renderer.hs
@@ -454,12 +454,10 @@ addUnique :: Bus -> UniqueName -> Renderer ApplicationInfo
 addUnique bus n = do
     let ai = ApplicationInfo NoColumn Set.empty Set.empty
     existing <- getsApps (Map.lookup n) bus
-    case existing of
-        Nothing -> return ()
-        Just _  -> warn $ concat [ "Unique name '"
-                                 , unUniqueName n
-                                 , "' apparently connected to the bus twice"
-                                 ]
+    forM_ existing $ const $ warn $ concat [ "Unique name '"
+                                           , unUniqueName n
+                                           , "' apparently connected to the bus twice"
+                                           ]
     modifyApps bus $ Map.insert n ai
     return ai
 
@@ -691,16 +689,14 @@ processMessage bus dm@(Detailed _ m _ _) = do
   where advance = advanceBy eventHeight -- FIXME: use some function of timestamp?
         returnOrError f = do
             call <- findCallCoordinates bus (inReplyTo m)
-            case call of
-                Nothing    -> return ()
-                Just (dm', (x,y)) -> do
-                    advance
-                    relativeTimestamp dm
-                    memberName dm' True
-                    f dm
-                    let duration = deTimestamp dm - deTimestamp dm'
-                    returnArc bus dm x y duration
-                    addMessageRegion dm
+            forM_ call $ \(dm', (x,y)) -> do
+                advance
+                relativeTimestamp dm
+                memberName dm' True
+                f dm
+                let duration = deTimestamp dm - deTimestamp dm'
+                returnArc bus dm x y duration
+                addMessageRegion dm
 
 processNOC :: Bus
            -> NOC
diff --git a/Bustle/StatisticsPane.hs b/Bustle/StatisticsPane.hs
index 3e4d3b5..b53335e 100644
--- a/Bustle/StatisticsPane.hs
+++ b/Bustle/StatisticsPane.hs
@@ -23,7 +23,7 @@ module Bustle.StatisticsPane
   )
 where
 
-import Control.Monad (forM_)
+import Control.Monad (forM_, void)
 import Text.Printf
 import Graphics.UI.Gtk
 import Bustle.Missing (formatSize)
@@ -109,13 +109,12 @@ addStatColumn :: TreeView
               -> String
               -> (a -> Marquee)
               -> IO ()
-addStatColumn view store title f = do
+addStatColumn view store title f = void $ do
     col <- treeViewColumnNew
     treeViewColumnSetTitle col title
     renderer <- addTextRenderer col store True f
     set renderer [ cellXAlign := 1 ]
     treeViewAppendColumn view col
-    return ()
 
 addTextStatColumn :: TreeView
                   -> ListStore a
diff --git a/Bustle/UI.hs b/Bustle/UI.hs
index 44abafb..67583d6 100644
--- a/Bustle/UI.hs
+++ b/Bustle/UI.hs
@@ -23,6 +23,7 @@ module Bustle.UI
   )
 where
 
+import Control.Monad (void)
 import Control.Monad.Reader
 import Control.Monad.State
 import Control.Monad.Except
@@ -302,7 +303,7 @@ recorderRun wi target filename r = C.handle newFailed $ do
 
     stopActivatedId <- wiStop wi `on` buttonActivated $ monitorStop monitor
     handlerId <- monitor `on` monitorMessageLogged $ updateLabel
-    _stoppedId <- monitor `on` monitorStopped $ \domain code message -> do
+    void $ monitor `on` monitorStopped $ \domain code message -> do
         handleError domain code message
 
         signalDisconnect stopActivatedId
@@ -314,8 +315,6 @@ recorderRun wi target filename r = C.handle newFailed $ do
 
         hadOutput <- fmap (/= 0) (readIORef n)
         finished hadOutput
-
-    return ()
   where
     newFailed (GError domain code message) = do
         finished False
@@ -391,7 +390,7 @@ finishedRecording wi tempFilePath producedOutput = do
         spinnerStop (wiSpinner wi)
 
     if producedOutput
-      then do
+      then void $ do
         -- TODO: There is a noticable lag when reloading big files. It would be
         -- nice to either make the loading faster, or eliminate the reload.
         loadLogWith (return wi) (RecordedLog tempFilePath)
@@ -401,7 +400,6 @@ finishedRecording wi tempFilePath producedOutput = do
         io $ do
             widgetSetSensitivity saveItem True
             saveItem `on` buttonActivated $ showSaveDialog wi (return ())
-        return ()
       else do
         setPage wi InstructionsPage
         putInitialWindow wi
@@ -671,8 +669,7 @@ displayLog wi@WindowInfo { wiWindow = window
            logDetails
            sessionMessages
            systemMessages
-           rr = do
-  io $ do
+           rr = io $ void $ do
     wiSetLogDetails wi logDetails
 
     hiddenRef <- newIORef Set.empty
@@ -708,8 +705,6 @@ displayLog wi@WindowInfo { wiWindow = window
 
         updateDisplayedLog wi rr'
 
-  return ()
-
 showOpenDialog :: Window
                -> B ()
 showOpenDialog window = embedIO $ \r -> do
diff --git a/Bustle/UI/Canvas.hs b/Bustle/UI/Canvas.hs
index 51d69f4..0257753 100644
--- a/Bustle/UI/Canvas.hs
+++ b/Bustle/UI/Canvas.hs
@@ -32,7 +32,7 @@ where
 
 import Data.Maybe (isNothing)
 import Data.IORef
-import Control.Monad (forM_, when)
+import Control.Monad (forM_, when, void)
 
 import Graphics.UI.Gtk
 import Graphics.Rendering.Cairo (Render, translate)
@@ -92,7 +92,7 @@ incdec (+-) f adj = do
 setupCanvas :: Eq a
             => Canvas a
             -> IO ()
-setupCanvas canvas = do
+setupCanvas canvas = void $ do
     let layout = canvasLayout canvas
 
     -- Scrolling
@@ -133,7 +133,6 @@ setupCanvas canvas = do
         _           -> stopEvent
 
     layout `on` draw $ canvasDraw canvas
-    return ()
 
 canvasInvalidateArea :: Canvas a
                      -> Int
@@ -174,12 +173,10 @@ canvasClampAroundSelection canvas = do
     when (isNothing id_) $ do
         id' <- flip idleAdd priorityDefaultIdle $ do
             rs <- readIORef $ canvasSelection canvas
-            case rsCurrent rs of
-                Nothing -> return ()
-                Just (Stripe top bottom, _) -> do
-                    vadj <- layoutGetVAdjustment $ canvasLayout canvas
-                    let padding = (bottom - top) / 2
-                    adjustmentClampPage vadj (top - padding) (bottom + padding)
+            forM_ (rsCurrent rs) $ \(Stripe top bottom, _) -> do
+                vadj <- layoutGetVAdjustment $ canvasLayout canvas
+                let padding = (bottom - top) / 2
+                adjustmentClampPage vadj (top - padding) (bottom + padding)
 
             writeIORef idRef Nothing
             return False
diff --git a/Bustle/UI/OpenTwoDialog.hs b/Bustle/UI/OpenTwoDialog.hs
index afb2217..f9e1e44 100644
--- a/Bustle/UI/OpenTwoDialog.hs
+++ b/Bustle/UI/OpenTwoDialog.hs
@@ -23,7 +23,7 @@ module Bustle.UI.OpenTwoDialog
 where
 
 import Data.Maybe (isJust, isNothing, fromJust)
-import Control.Monad (when)
+import Control.Monad (when, void)
 
 import Graphics.UI.Gtk
 
@@ -42,9 +42,8 @@ propagateCurrentFolder d1 d2 = d1 `on` currentFolderChanged $ do
     f1 <- fileChooserGetCurrentFolder d1
     f2 <- fileChooserGetCurrentFolder d2
     otherFile <- fileChooserGetFilename d2
-    when (isNothing otherFile && f1 /= f2 && isJust f1) $ do
+    when (isNothing otherFile && f1 /= f2 && isJust f1) $ void $
         fileChooserSetCurrentFolder d2 (fromJust f1)
-        return ()
 
 setupOpenTwoDialog :: Window
                    -> (FilePath -> FilePath -> IO ())
diff --git a/Bustle/Util.hs b/Bustle/Util.hs
index 425f2aa..edb4c92 100644
--- a/Bustle/Util.hs
+++ b/Bustle/Util.hs
@@ -30,6 +30,7 @@ module Bustle.Util
 where
 
 import Control.Monad.Trans (MonadIO, liftIO)
+import Control.Monad
 import Debug.Trace (trace)
 import System.IO (hPutStrLn, stderr)
 import Foreign.C.String
@@ -39,7 +40,7 @@ import Bustle.Translation (__)
 
 -- Escape hatch to log a value from a non-IO monadic context.
 traceM :: (Show a, Monad m) => a -> m ()
-traceM x = trace (show x) $ return ()
+traceM = void . return . trace . show
 
 -- Log a warning which isn't worth showing to the user, but which might
 -- interest someone debugging the application.