Function eigensystem_3 

pub fn eigensystem_3<S>(matrix: Matrix3<S>) -> [Option<(S, Vector3<S>)>; 3]
where
    S: Real + NumCast + RelativeEq<Epsilon = S> + Debug,

Return the (real-valued) eigenvalues and eigenvectors (eigenpairs) of a diagonalizable 3x3 matrix.

Uses the Francis (implicit QR) algorithm.

Returns [Some((0, Vector2::zero())), None] if the matrix is the zero matrix:

let mat = Matrix3::<f32>::zero();
assert_eq!(eigensystem_3 (mat), [Some ((0.0, Vector3::zero())), None, None]);