fieldAccess2.hs

data Tile =
  Empty {position :: Position} |
  Wall {position :: Position}
data Position =
  Position
    {
      x :: Double,
      y :: Double
    }

-- position :: Tile -> Position
-- x :: Position -> Double

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

tilesFiltered r =
  [tile |
    tile <- tiles,
    (x (position tile) ** 2 + y (position tile) ** 2) ** (1/2) < r
  ]