title: `isNan` in Objective-C
body: <p>Is there a function like <code>isNan</code> (Javascript example) for Objective-C?</p>
  <p>I just noticed this code is causing to display <code>Nan %</code>, so I need to detect is a value is NAN so I could change it to <code>0</code>.</p>
  <pre><code>[portefeuillePercentWaarde setText:[NSString stringWithFormat:@&quot;%.2f%%&quot;, verschilPrencentage]];
  </code></pre>