">ar1</code> and <code class="code">ar2</code> are the same.
   Raise <code class="code"><span class="constructor">Invalid_argument</span> <span class="string">"Weak.blit"</span></code> if <code class="code">off1</code> and <code class="code">len</code> do
   not designate a valid subarray of <code class="code">ar1</code>, or if <code class="code">off2</code> and <code class="code">len</code>
   do not designate a valid subarray of <code class="code">ar2</code>.<br>
</div>
<br>
<h6 id="6_Weakhashtables">Wea