text: from intrinsics import car, cdr, nil
  
  def has_ghost_at(world, x, y):
      return has_ghost_from_list(world[2], x, y)
  
  def has_ghost_from_list(ghost_list, x, y):
      if nil(ghost_list):
          return 0
      else:
          ghost = ghost_list[0]
          ghost_coord = ghost[1]
          if ghost_coord[0] == x:
              if ghost_coord[1:] == y:
                  return 1
              else:
                  return has_ghost_from_list(ghost_list[1:], x, y)
          else:
              return has_ghost_from_list(ghost_list[1:], x, y)
  