>Invalid_argument</code> if len &lt; 0.</li>
</ul>
</div>

<pre><span id="VALappend"><span class="keyword">val</span> append</span> : <code class="type">'a list -&gt; 'a list -&gt; 'a list</code></pre><div class="info ">
<div class="info-desc">
<p>Concatenate two lists.  Same as the infix operator <code class="code">@</code>.
   Not tail-recursive (length of the first argument).</p>
</div>
</div>

<pre><span id="VALrev_append"><span class="keyword">val</span> rev_append</span> : <code class="type">'a list -