title: NSNumber doubleValue returns NaN
body: <p>As the screenshot below shows, <code>nsdt</code>'s value is approximately 0.033, but the <code>doubleValue</code> method returned NaN. Why is it not returning 0.033?</p>
  
  <pre><code>-(void) updateWithDTNSTime:(NSNumber*) nsdt;
  {
      double dt = [nsdt doubleValue];
  
      if(isnan(dt))
      {
          printf("nan\n");
      }
  
      [self updateWithDTime:dt];
  }
  </code></pre>
  
  <p><img src="https://ww4.sinaimg.cn/mw690/a0e78242gw1dwo2xie9s0j.jpg" alt=""></p>