unctions is defined in terms of
    indices and positions. These are depicted and described
    as follows.</p>

<pre class="verbatim">positions  0   1   2   3   4    n-1    n
           +---+---+---+---+     +-----+
  indices  | 0 | 1 | 2 | 3 | ... | n-1 |
           +---+---+---+---+     +-----+</pre><ul>
<li>An <em>index</em> <code class="code">i</code> of <code class="code">s</code> is an integer in the range [<code class="code">0</code>;<code class="code">n-1</code>].
       It represents the <code cla