@Override
    public Matrix clone()
    {
        return new Matrix(single.clone());
    }
@Test
    void testConstructionAndCopy() throws Exception
    {
        Matrix m1 = new Matrix();
        assertMatrixIsPristine(m1);

        Matrix m2 = m1.clone();
        assertNotSame(m1, m2);
        assertMatrixIsPristine(m2);
    }