title: what is the 'cons' to add an item to the end of the list?
body: <p>what's the typical way to add an item to the end of the list?  </p>
  
  <p>I have a list (1 2 3) and want to add 4 to it (where 4 is the result of an evaluation (+ 2 2))</p>
  
  <pre><code>(setf nlist '(1 2 3))  
  (append nlist (+ 2 2))  
  </code></pre>
  
  <p>This says that append expects a list, not a number. How would I accomplish this?</p>