greatest common divisor of I and J.
        </li>
        <li>
          <b>I4_HUGE</b> returns a "huge" I4.
        </li>
        <li>
          <b>I4_LENGTH</b> computes the number of characters needed to print an integer.
        </li>
        <li>
          <b>I4_SWAP</b> switches two I4's.
        </li>
        <li>
          <b>I4_TO_A</b> returns the I-th alphabetic character.
        </li>
        <li>
          <b>I4_TO_AMINO_CODE</b> converts an integer to an amino code.
        </li>
        <li>