title: LISP Loop through list
body: <p>I have a function "power" which gives me square of the number and the other functions needs to sum every number squared from a list. But it tells me undefined function I and i really can't make it work .</p>
  
  <pre><code>(defun power (x)
    (if (numberp x) (* x x) 0)
  )
  (defun sum (l)
    (loop for i in l do(setq s(+ (power (i)) s)))
      print s)
  </code></pre>