ite"><pre><span></span><code> <span class="nv">isdigit</span><span class="ss">(</span><span class="mi">3</span><span class="nv">f</span><span class="ss">)</span> <span class="nv">returns</span> .<span class="nv">true</span>. <span class="k">if</span> <span class="nv">character</span> <span class="nv">is</span> <span class="nv">a</span> <span class="nv">digit</span> <span class="ss">(</span><span class="mi">0</span>,<span class="mi">1</span>,...,<span class="mi">9</span><span class="ss">)</span>
 <span class