Design of new basis for machines / scalaz-stream that does not require separate plan type

machines.hs

-- Type-aligned sequence catenable queue supporting O(1) append, snoc, uncons
-- Don't need it to be a dequeue (unsnoc not needed)
data TCQueue c a b -- c is the category, a is starting type, b is ending type

type Channel f a b = TCQueue (Transition f) a b
type Process f b = Channel f () b

data Transition f a b where
  Bind :: (a -> Process f b) -> Transition f a b
  OnHalt :: (Cause -> Process f b) -> Transition f a b 
  Emit :: b -> Transition f a b
  Await :: f b -> Transition f a (Either Cause b)
  Halt :: Cause -> Transition f a b

data Cause = Normal | Error String

onHalt :: Channel f a b -> (Cause -> Process f b) -> Channel f a b
onHalt h t = h |> OnHalt t

append :: Channel f a b -> Process f b -> Channel f a b
append a b = onHalt a go where
  go Normal = b
  go cause = singleton (Halt cause)

through :: Channel f a b -> Channel f b c -> Channel f a c
through = ><

instance Monad (Process f b) where
  return a = singleton (Emit a)
  (>>=) p f = p |> Bind f

step :: Cause -> a -> Channel f a b -> Process f (Either Cause (b, Channel f a b))
step = ...