 of the points above. The details of streaming and how many times the sequence is iterated over are frankly a pain to deal with, unfortunately. Given how much there is to implement already, we&#39;ll come back to those.</p>  <p>Let&#39;s have a look at some tests. First, here&#39;s a simple &quot;positive&quot; test - we&#39;re starting with an array of integers, and using a lambda expression to only include elements less than 4 in the output. (The word &quot;filter&quot; is omnipresent but unfortunate. It&