ns a new weak array of length <code class="code">n</code>.
   All the pointers are initially empty.  Raise <code class="code"><span class="constructor">Invalid_argument</span></code>
   if <code class="code">n</code> is negative or greater than <a href="Sys.html#VALmax_array_length"><code class="code"><span class="constructor">Sys</span>.max_array_length</code></a><code class="code">-1</code>.<br>
</div>

<pre><span id="VALlength"><span class="keyword">val</span> length</span> : <code class="type">'a <a hre