{-# RULES
"fold/build" foldr k z (build g) = g k z
    #-}

{-# RULES
"fusable/aux"
    fusable x (aux y) =
        faux x y
    #-}

{-# RULES
"map/map"
    map
        f
        (map g xs) =
        map
            (f . g)
            xs
    #-}
