title: How to strip everything except digits from a string in Scala (quick one liners)
body: <p>This is driving me nuts... there <strong>must</strong> be a way to strip out all non-digit characters (or perform other simple filtering) in a String.</p>
  
  <p>Example: I want to turn a phone number ("+72 (93) 2342-7772" or "+1 310-777-2341") into a simple numeric String (not an Int), such as "729323427772" or "13107772341".</p>
  
  <p>I tried <code>"[\\d]+".r.findAllIn(phoneNumber)</code> which returns an Iteratee and then I would have to recombine them into a String somehow... seems horribly wasteful.</p>
  
  <p>I also came up with: <code>phoneNumber.filter("0123456789".contains(_))</code> <strong>but</strong> that becomes tedious for other situations. For instance, removing all punctuation... I'm really after something that works with a regular expression so it has wider application than just filtering out digits.</p>
  
  <p>Anyone have a fancy Scala one-liner for this that is more direct?</p>