</dt>
	<dd>
		Returns the first value of the set.
	</dd>
	
	<dt><code><b>insert</b>(value [, previous])</code></dt>
	<dd>
		Inserts <code>value</code> in the set after the value <code>previous</code>.
		If <code>previous</code> is not provided then <code>value</code> is inserted as the last value of the set.
		<code>value</code> is returned if successfully inserted.
		If <code>previous</code> does not belong to the set or <code>value</code> is already inserted then the call has no effect and no value is ret