  <p>Returns a sequence formed from repeated lazy applications of <code>next</code> to a
mutable <code>state</code>.</p>

<p>The elements of the sequence are obtained by invoking <code>next</code> with a mutable
state. The same state is passed to all invocations of <code>next</code>, so subsequent
calls will see any mutations made by previous calls. The sequence ends when
<code>next</code> returns <code>nil</code>. If <code>next</code> never returns <code>nil</code>, the sequence is
infinite.</p>

<p>This f