grammars, alternatives are often of the form <code class="computeroutput"><span class="special">*(</span><span class="identifier">a</span> <span class="special">|</span> <span class="identifier">b</span>
        <span class="special">|</span> <span class="identifier">c</span> <span class="special">|</span> <span class="identifier">d</span><span class="special">)</span></code>.
        The input iterator moves on and is never stuck at the beginning. Let's look
        at a Pascal snippet for example:
      <