   Sequence</a> is the most basic concept. <a class="link" href="concepts/bidirectional_sequence.html" title="Bidirectional Sequence">Bidirectional
        Sequence</a> is a refinement of <a class="link" href="concepts/forward_sequence.html" title="Forward Sequence">Forward
        Sequence</a>. <a class="link" href="concepts/random_access_sequence.html" title="Random Access Sequence">Random
        Access Sequence</a> is a refinement of <a class="link" href="concepts/bidirectional_sequence.html" title="Bid