</code></pre><div class="info ">
<code class="code"><span class="constructor">Weak</span>.check ar n</code> returns <code class="code"><span class="keyword">true</span></code> if the <code class="code">n</code>th cell of <code class="code">ar</code> is
   full, <code class="code"><span class="keyword">false</span></code> if it is empty.  Note that even if <code class="code"><span class="constructor">Weak</span>.check ar n</code>
   returns <code class="code"><span class="keyword">true</span></code>, a subse