title: Counting numbers in a list
body: <p>Is there anyone who can help me to write a function in common LISP that counts the numbers in a list?
  The code that I have written is below, but it does not work!</p>
  
  <pre><code>(defun count-numbers(lst)
      (let(result()))
      (dolist(number lst)
      (push number result))
      (length result))
  </code></pre>
  
  <p>For example, when I enter this query <code>"(count'(r 4 f d w 2 3 4 1 z))"</code>, I must get 5.</p>