riants:</p>
<ul>
<li>The list is not empty.</li>
<li>Concatenating its elements using <code class="code">sep</code> as a separator returns a
      string equal to the input (<code class="code">concat&nbsp;(make&nbsp;1&nbsp;sep)<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(split_on_char&nbsp;sep&nbsp;s)&nbsp;=&nbsp;s</code>).</li>
<li>No string in the result contains the <code class="code">sep</code> character.</li>
</ul>
</div>
<ul class="info-attributes">
<li><b>Since</b> 4.05.0</li>
</ul>
</div>
<h2 id="trans