Function magnitude

tests/test_sparse_vec.rs:13–19

()

#[test]
fn magnitude() {
    let (a, _) = create();
    assert_relative_eq!(
        a.magnitude(),
        (0.5_f64.powf(2.0) + 0.75_f64.powf(2.0)).sqrt()
    );
}

#[test]
fn scale() {