title: Lisp: Why is it saying that I'm only giving my function one argument?
body: <p>The code: </p>
  
  <pre><code>(defun len (x count)
    (cond ((null x) ())
          (t (+ count 1)
             (len (cdr x)))))
  </code></pre>
  
  <p>I try to call this function with (len '(a b c) 0) and I get an error saying that I'm only sending the function one argument and it requires two.</p>
  
  <p>What am I doing wrong? I'm especially confused because I ran the function once with no errors using this exact same code, but then it decided that it didn't want to work anymore.</p>