Use `om when` from Control.Monad.Extra instead of `whenM`.

factorial/factorial.cabal

@@ -18,8 +18,9 @@ executable factorial
   -- other-extensions:
   ghc-options:         -threaded
   build-depends:       base         >=4.6 && <4.9,
+                       monad-extras >=0.5 && <0.6,
                        stm          >=2.4 && <2.5,
-                       hsqml >=0.3 && <0.4,
-                       text  >=1.2 && <1.3
+                       text         >=1.2 && <1.3,
+                       hsqml        >=0.3 && <0.4
   -- hs-source-dirs:
   default-language:    Haskell2010

factorial/factorial.hs

@@ -6,6 +6,7 @@ import Control.Concurrent (forkIO, killThread, myThreadId)
 import Control.Concurrent.STM
 import Control.Exception (evaluate, mask_)
 import Control.Monad
+import Control.Monad.Extra (om)
 import Data.IORef
 import Data.Maybe
 import Data.Text (Text)
@@ -13,11 +14,6 @@ import Graphics.QML
 
 import qualified Data.Text as T
 
--- How are these not in Control.Monad?
-whenM, unlessM :: Monad m => m Bool -> m () -> m ()
-whenM   mcond mtrue  = mcond >>= flip when   mtrue
-unlessM mcond mfalse = mcond >>= flip unless mfalse
-
 main :: IO ()
 main = do
    state  <- newIORef $ T.pack ""
@@ -38,7 +34,7 @@ main = do
             evaluate out
             writeIORef state out
             mask_ $ fireSignal skey obj
-            atomically $ whenM ((== Just tid) <$> readTMVar tidVar) $
+            atomically $ om when ((== Just tid) <$> readTMVar tidVar) $
                void $ swapTMVar tidVar Nothing
       ]