title: Replace item in association list in elisp
body: <p>I have an alist in emacs lisp like:</p>
  
  <pre><code>(setq a1
   '((:k1 . 1)
     (:k2 . 2)
     (:k3 . 3)))
  </code></pre>
  
  <p>and i want to change value of :k1 to 10, like <code>(:k1 . 10)</code>. How do i do that?</p>
  
  <p>I tried <code>(setf (assoc :k1 a1) '(:k1 . 10))</code> - it didn't work.</p>