{-# LANGUAGE Arrows #-}
foo f = proc a ->
  do f -< a

bazbaz f g h = proc (a, b, c) ->
  do x
       <- f b -< a
     y <-
       g b -< b
     z <-
       h
         x
         y
       -< (
           a,
           b,
           c
       )
     returnA -<
       (x, y, z)

bar f = proc x -> do {f -< x} <+> do f -< x