st. Raise
   <code class="code"><span class="constructor">Failure</span> <span class="string">"hd"</span></code> if the list is empty.<br>
</div>
<pre><span id="VALtl"><span class="keyword">val</span> tl</span> : <code class="type">'a list -&gt; 'a list</code></pre><div class="info">
Return the given list without its first element. Raise
   <code class="code"><span class="constructor">Failure</span> <span class="string">"tl"</span></code> if the list is empty.<br>
</div>
<pre><span id="VALnth"><span class="