loop example

tests/Tests/Loop.hs

@@ -0,0 +1,35 @@
+{-# LANGUAGE DataKinds             #-}
+{-# LANGUAGE FlexibleContexts      #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+module Tests.Loop
+  ( runFixLoop
+  , runTailLoop
+  , runForeverLoop
+  ) where
+
+import           Control.Monad       (forever)
+import           Control.Monad.Freer
+import           Data.Function       (fix)
+
+-- | This loops forever as expected
+fixLoop :: Member IO r => Eff r ()
+fixLoop = fix $ \fxLoop -> do
+  send $ putStrLn "fixLoop"
+  fxLoop
+
+runFixLoop :: IO ()
+runFixLoop = runM fixLoop
+
+-- | This loops as expected
+tailLoop :: Member IO r => Eff r ()
+tailLoop = send (putStrLn "tailLoop") >> tailLoop
+
+runTailLoop :: IO ()
+runTailLoop = runM tailLoop
+
+-- | This <<loop>>s.
+foreverLoop ::  Member IO r => Eff r ()
+foreverLoop = forever $ send $ putStrLn "loop"
+
+runForeverLoop :: IO ()
+runForeverLoop = runM foreverLoop