ss="code">i</code>th byte (character) of <code class="code">s</code> which can be
       accessed using the constant time string indexing operator
       <code class="code">s.[i]</code>.</li>
<li>A <em>position</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</code>]. It represents either the point at the beginning of
       the string, or the point between two indices, or the point at
       the end of the st