title: How is my LISP function an unbound variable?
body: <p>I define a function in LISP, and it defines correctly. But whenever I try to call it, I get an error saying "The variable FACTORIAL is unbound." </p>
  
  <p>I have tried this on both OS X and Windows 7, on LispWorks and Allegro. The function is - </p>
  
  <pre><code>(defun factorial (x)
     (if (= 1 x) 1
         (* x factorial (- 1 x))))
  </code></pre>
  
  <p>Any help is appreciated.</p>