Points and Tiles

pack [P = PointRep in TileWRT[P]]

pack [T <= PointRep = TileRep in TileWRT2[P, T]]
  {mktile = fun(x:Int, y: Int, hor: Int, ver: Int)
     {x=x, y-y, hor=hor, ver=ver},
      origin = fun(t: TileRep) t,
      hor = fun(t: TileRep) t.hor,
      ver = fun(t: TileRep) t.ver}

fun(tilePack: Tile)
   open tilePack as t[pointRep][tileRep]
      let f = fun(p: pointRep) ...
      in f(t.tile(0, 0, 1, 1))