title: NSMutableString replaceOccurrencesOfString replacing whole words
body: <p>Is there a way to use <code>replaceOccurrencesOfString</code> (from <code>NSMutableString</code>) to replace whole words?</p>
  
  <p>For example, if I want to replace all occurrences of a fraction in a string, like "1/2", I'd like that to match only that specific fraction. So if I had "11/2", I would <strong>not</strong> want that to match my "1/2" rule.</p>
  
  <p>I've been trying to look for answers to this already, but I am having no luck.</p>