import Clash.Prelude
-- import Clash.Explicit.Testbench

data SList (n :: Nat) a
  = SNil
  | SCons !a !(SList a)
  deriving (NFDataX, Generic)

isSNil :: SList a -> Bool
isSNil sl = case sl of
  SNil -> True
  _ -> False

tf :: SList Int -> Int -> (SList Int, Maybe Bool)
tf s inp = case s of
  SCons _ s' -> (s', Just False)
  SNil -> (SNil, Just True)

mon
  :: SystemClockResetEnable
  => Signal System Int
  -> Signal System (Maybe Bool)
mon = mealy tf SNil

topEntity
  :: Clock System
  -> Reset System
  -> Enable System
  -> Signal System Int
  -> Signal System (Maybe Bool)
topEntity = exposeClockResetEnable mon