title: No operation in Scheme Language
body: <p>I am  having some trouble in how to define no operation in scheme language </p>
  
  <p>like ; in c</p>
  
  <p>i want to do something like this:</p>
  
  <pre><code>   (cond
     [(null? exp)  nop ]
      .....
     )
  </code></pre>
  
  <p>if i leave it empty it wiil return #t
  thanks!</p>