title: How to write routing.yml when you have more than two query to omit
body: <p>I have routing like this.</p>
  
  <pre><code>acme_apiByDate_homepage:
      pattern: /api/byDate/{date}/{page}/{limit}
      defaults: { _controller: AcmeTopBundle:Api:byDate,date:"",page:0,limit:50, _format: xml  } 
  </code></pre>
  
  <p>normal URL is like this</p>
  
  <p>/api/byDate/2013-04-12/0/40</p>
  
  <p>However sometimes I would like to omit the date.</p>
  
  <p>But, this shows error</p>
  
  <p>/api/byDate//0/40</p>
  
  <p>I know I can omit the last parameter, but I want to omit the middle parameter.</p>
  
  <p>How can I make it?</p>