="mi">0</span><span class="p">,</span><span class="o">-</span><span class="mi">1</span><span class="p">);</span>  <span class="c1">// remember relative locations of neighbors above and below</span>
<span class="n">below</span><span class="o">=</span><span class="n">loc</span><span class="p">.</span><span class="n">cache_location</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span>
<span class="o">++</span><span class="n">loc</span