{-# LANGUAGE Arrows #-}

bar f = proc a ->
  do b <- f -< a

barbar f g = proc a ->
  do b <- f -< a
     returnA -< b

barbaz f g = proc (a, b) ->
  do c <- f -< a
     d <- g -< b

bazbar f = proc a ->
  do a
       <-
       f
       -<
       a

foo =
  proc x -> do
    returnA -< x
   1

foo a =
  proc x ->
    case Left x of
      Left x -> returnA -< x
     a