s.</p>

<h2>Behavior</h2>

<h3>Fields</h3>

<dl>

	<dt><code><b>firstkey</b></code>: userdata</dt>
	<dd>
		Special value used as the key that maps the first value of the set.
	</dd>

</dl>

<h3>Methods</h3>

<dl>

	<dt><code><b>contains</b>(value)</code></dt>
	<dd>
		Return true if a <code>value</code> belongs to the set or false otherwise.
	</dd>
	
	<dt><code><b>empty</b>()</code></dt>
	<dd>
		Return true if there is no value inserted in the set or false otherwise.
	</dd>
	
	<dt><code><b>first</b>()</code>