fieldAccess1.hs

data Tile = Empty Position | Wall Position
data Position = Position Double Double

tiles :: [Tile]
tiles =
  [Wall (Position 0 0), Wall (Position 0 1), Wall (Position 0 2)]

tilesFiltered r = [tile | tile <- tiles, norm tile < r]

norm :: Tile -> Double
norm tile =
  (x ** 2 + y ** 2) ** (1/2)
  where
    Position x y =
      case tile of
        Empty p -> p
        Wall p -> p