title: Add lists to a list lisp
body: <p>I'm new to Lisp and I'm having trouble figuring out how I add a list to another list. I start with an empty list, and I have to add new lists, each containing three elements. For example,</p>
  
  <p><code>(add '(1 2 3) '())</code></p>
  
  <p>would return <code>((1 2 3))</code> [let's call it new-list], and adding a new list to this new one, for example</p>
  
  <p><code>(add '(4 5 6) new-list)</code></p>
  
  <p>would return <code>((1 2 3) (4 5 6))</code> or <code>((4 5 6) (1 2 3))</code></p>
  
  <p>I've tried a few different ways, but so far the closest I've come up was <code>((((1 2 3)) (4 5 6)) (7 8 9))</code></p>
  
  <p>I was using something like this:</p>
  
  <p><code>(defun add (lst new-let)
          (if (null lst) '()
          (setf new-lst (cons new-lst (cons lst '()))))</code></p>