Reflect point about the line x = -y
reflectPointXMinusY :: (Num a) => Point a -> Point a
reflectPointXMinusY (P x y) =
    P (-y) (-x)

-
reflectPointXMinusY :: (Num a) => Point a -> Point a
reflectPointXMinusY (P x y) =
    P (-y) (-x)
reflectPointXMinusY (P x y) =
    P (-y) (-x)