title: 'Do nothing' operator in Oz
body: <p>As a part of a learning course, i was making a procedure that took lists as parameters and then operated on their contents. It went like this:</p>
  
  <pre><code>proc {myProc A B}
      case B of H|T then
          %do something
          {myProc A T}
      end
  end
  </code></pre>
  
  <p>However, when i have tried executing it, i encountered failures when <code>B</code> is an ampty list (that is, <code>nil</code>). Why is that?</p>
  
  <p>What should i do in order to do nothing if <code>B</code> is nil? As far as i know, adding empty <code>else</code> clause will result in compilation error.</p>