title: Lisp: IF condition using AND operator
body: <p>I making this function. </p>
  
  <pre><code>(f 3 4) (sum = 7) 
  (f 'a 'b) (not num!) 
  </code></pre>
  
  <p>My problem is how can I make if condition using and operator.</p>
  
  <p>I try....</p>
  
  <ol>
  <li><p><code>(IF (and (typep a 'integer) (typep b 'integer)) (1) (0))</code></p></li>
  <li><p><code>(IF (and ((typep a 'integer)) ((typep b 'integer))) (1) (0))</code></p></li>
  <li><p><code>(IF ((and ((typep a 'integer)) ((typep b 'integer)))) (1) (0))</code></p></li>
  </ol>
  
  <p>But it doesn't work.
  (1) (0) is  I set it temporarily.</p>
  
  <p>Could I get some lisp syntax help?</p>