-- | General purpose timers.module Language.Atom.Common.Timer  ( Timer  , timer  , start  , whenDone  , periodicTimer  ) whereimport Language.Atom-- | A Timer.data Timer = Timer (Var Int)-- | Creates a new timer, with a name and a count.timer :: Name -> System Timertimer name = scope name $ do  timer <- int "timer" 0  rule "decrement" $ do    when $ value timer >. 0    timer <== value timer - 1  return $ Timer timer-- | Starts a Timer.  A Timer can be restarted at any time.start :: Timer -> Int -> Action ()start (Timer t) time = do  lift $ assert "positiveTime" $ time >= 0  t <== intC (max 0 (time - 1))-- | Guard condition enabled with Timer completes.whenDone :: Timer -> Action ()whenDone (Timer t) = when $ value t ==. 0-- | Creates a periodic, free runnning timer.  Returns a guard condition when Timer resets.periodicTimer :: Name -> Int -> System (Action ())periodicTimer name count = scope name $ do  assert "positiveNumber" $ count >= 0  t <- timer name  rule "reset" $ do    whenDone t    start t count  return $ whenDone t