Fix warnings in examples (#257)

Author: dpwiz

examples/EventWatch.hs

@@ -14,6 +14,8 @@ module EventWatch where
 
 import SDL
 
+import Control.Monad (void)
+
 main :: IO ()
 main = do
   initializeAll
@@ -28,8 +30,8 @@ main = do
     , windowInitialSize     = V2 800 600
     , windowVisible         = True
   }
-  renderer <- createRenderer window (-1) defaultRenderer
-  addEventWatch $ \ev ->
+  _renderer <- createRenderer window (-1) defaultRenderer
+  void . addEventWatch $ \ev ->
     case eventPayload ev of
       WindowSizeChangedEvent sizeChangeData ->
         putStrLn $ "eventWatch windowSizeChanged: " ++ show sizeChangeData

examples/UserEvents.hs

@@ -1,6 +1,7 @@
 module UserEvents where
 
 import Control.Concurrent (myThreadId)
+import Control.Monad (void)
 import Data.Maybe (Maybe(Nothing))
 import Data.Word (Word32)
 import qualified Data.Text as Text
@@ -26,7 +27,7 @@ main = do
   case registeredEvent of
     Nothing -> putStrLn "Fatal error: unable to register timer events."
     Just registeredTimerEvent -> do
-      addTimer 1000 $ mkTimerCb registeredTimerEvent
+      void . addTimer 1000 $ mkTimerCb registeredTimerEvent
       putStrLn "press q at any time to quit"
       appLoop registeredTimerEvent
 
@@ -40,7 +41,7 @@ mkTimerCb (RegisteredEventType pushTimerEvent _) interval = do
   return $ Reschedule interval
 
 appLoop :: RegisteredEventType TimerEvent -> IO ()
-appLoop (RegisteredEventType pushTimerEvent getTimerEvent) = waitEvent >>= go
+appLoop (RegisteredEventType _pushTimerEvent getTimerEvent) = waitEvent >>= go
   where
   go :: Event -> IO ()
   go ev =

examples/lazyfoo/Lesson02.hs

@@ -2,6 +2,7 @@
 module Lazyfoo.Lesson02 (main) where
 
 import Control.Concurrent (threadDelay)
+import Control.Monad (void)
 import Foreign.C.Types
 import SDL.Vect
 import qualified SDL
@@ -20,7 +21,7 @@ main = do
 
   helloWorld <- getDataFileName "examples/lazyfoo/hello_world.bmp" >>= SDL.loadBMP
 
-  SDL.surfaceBlit helloWorld Nothing screenSurface Nothing
+  void $ SDL.surfaceBlit helloWorld Nothing screenSurface Nothing
   SDL.updateWindowSurface window
 
   threadDelay 2000000

examples/lazyfoo/Lesson03.hs

@@ -27,7 +27,7 @@ main = do
       events <- SDL.pollEvents
       let quit = elem SDL.QuitEvent $ map SDL.eventPayload events
 
-      SDL.surfaceBlit xOut Nothing screenSurface Nothing
+      void $ SDL.surfaceBlit xOut Nothing screenSurface Nothing
       SDL.updateWindowSurface window
 
       unless quit loop

examples/lazyfoo/Lesson04.hs

@@ -56,7 +56,7 @@ main = do
                            _ -> mempty)
                     events
 
-      SDL.surfaceBlit currentSurface Nothing screenSurface Nothing
+      void $ SDL.surfaceBlit currentSurface Nothing screenSurface Nothing
       SDL.updateWindowSurface window
 
       unless quit (loop currentSurface)