all.empty;

                <span class="comment">% Inner loop over all other particles with higher ID</span>
                <span class="keyword">for</span> j = 1:drv.n_particles
                    p2 = drv.particles(j);
                    <span class="keyword">if</span> (p1.id &gt;= p2.id)
                        <span class="keyword">continue</span>;
                    <span class="keyword">end</span>

                    <span class="comment">% Check for existing interaction</span>
                 