streams B and C, and a fourth stream D is dependent on both B and C, the stream D will only update once if the value of A changes. This guarantees that the callback for stream D is never called with unstable values such as when B has a new value but C has the old value. Atomicity also bring the performance benefits of not recomputing downstreams unnecessarily.</p>
<p>You can prevent dependent streams from being updated by returning the special value <code>stream.HALT</code></p>
<pre><code class="lang-javasc