title: How to determine the meaning of nil in clojure?
body: <p>for example,</p>
  
  <pre><code>&gt; (some #{nil} #{nil 1 2 3})
  nil
  
  &gt; (some #{} #{nil 1 2 3})
  nil
  </code></pre>
  
  <p>I know I could use</p>
  
  <pre><code>(some nil? #{nil 1 2 3})
  </code></pre>
  
  <p>to check nil value. I can't think of any good example at the moment.</p>
  
  <p>But generally, when nil is returned， how do I determine if nil means nothing is found or the value nil is found?</p>