  <b>C4_MUL</b> multiplies two C4's.
        </li>
        <li>
          <b>C4_NEG</b> returns the negative of a C4.
        </li>
        <li>
          <b>C4_NORM_L1</b> evaluates the L1 norm of a C4.
        </li>
        <li>
          <b>C4_NORM_L2</b> evaluates the L2 norm of a C4.
        </li>
        <li>
          <b>C4_NORM_LI</b> evaluates the L-infinity norm of a C4.
        </li>
        <li>
          <b>C4_NORMAL_01</b> returns a unit pseudonormal C4.
        </li>
        <li>
          <b