step :: Placement -> Step -> Placement
step (Placement o pos) (Step t n) =
  let o' = turn t o
      pos' = move o' n pos
  in Placement o' pos'
step :: Placement -> Step -> Placement
step (Placement o pos) (Step t n) =
  let o' = turn t o
      pos' = move o' n pos
  in Placement o' pos'
step (Placement o pos) (Step t n) =
  let o' = turn t o
      pos' = move o' n pos
  in Placement o' pos'