title: CDR usage in lisp
body: <p>is it not possible to take a <code>cdr</code> of a <code>cdr</code>?
  i have this code and the last two statements returns a nil</p>
  
  <pre><code>CL-USER 31 : 1 &gt; (CHOICES 'PANTRY)
  ((NORTH KITCHEN) (WEST DINING-ROOM))
  
  CL-USER 32 : 1 &gt; (car(CHOICES 'PANTRY))
  (NORTH KITCHEN)
  
  CL-USER 33 : 1 &gt; (car(car(CHOICES 'PANTRY)))
  NORTH
  
  CL-USER 34 : 1 &gt; (cdr(CHOICES 'PANTRY))
  ((WEST DINING-ROOM))
  
  CL-USER 35 : 1 &gt; (car(cdr(cdr(CHOICES 'PANTRY))))
  NIL
  
  CL-USER 36 : 1 &gt; (cdr(cdr(CHOICES 'PANTRY)))
  NIL
  </code></pre>
  
  <p>In the last two statements I'm aiming for a <code>(DINING-ROOM)</code> result, they're two different ways i tried to get that.</p>