an class="k">typename</span> <span class="n">StepIterator</span><span class="o">&gt;</span>
<span class="k">class</span> <span class="nc">memory_based_2d_locator</span><span class="p">;</span>
</pre></div>
</div>
<p>The step of <code class="docutils literal"><span class="pre">StepIterator</span></code> must be the number of memory units (bytes or
bits) per row (thus it must be memunit advanceable). The class
<code class="docutils literal"><span class="pre">memory_based_2d_locator</span></code> is a wrapper 