{x} x {x}, {y} x y {x}, {y}, {z} x y z {x}, {y}, {z}, {w} x y z w ({x}, {y}, {z}), {w} x y z w (({real.x}, {real.y}, {real.z}), {real.w}), (({dual.x}, {dual.y}, {dual.z}), {dual.w}) real dual