lass="kw">[[</span><span class="no">arm</span>]])  <span class="kw">&lt;-</span> <span class="fl">1</span>
      <span class="kw">if</span> (<span class="fu"><a href="../../reference/sum_of.html">sum_of</a></span>(<span class="no">self</span>$<span class="no">theta</span>$<span class="no">n</span>) <span class="kw">&lt;</span> <span class="no">self</span>$<span class="no">first</span> - <span class="fl">1</span>) {
        <span class="fu">inc</span>(<span class="no">self</span>$<span class="no">theta</span