title: iPhone SDK << meaning?
body: <p>Hi another silly simple question. I have noticed that in certain typedefs in Apple's frameworks use the symbols <code>"&lt;&lt;"</code> can anyone tell me what that means?:</p>
  
  <pre>
  <code>
  enum {
      UIViewAutoresizingNone                 = 0,
      UIViewAutoresizingFlexibleLeftMargin   = 1 &lt;&lt; 0,
      UIViewAutoresizingFlexibleWidth        = 1 &lt;&lt; 1,
      UIViewAutoresizingFlexibleRightMargin  = 1 &lt;&lt; 2,
      UIViewAutoresizingFlexibleTopMargin    = 1 &lt;&lt; 3,
      UIViewAutoresizingFlexibleHeight       = 1 &lt;&lt; 4,
      UIViewAutoresizingFlexibleBottomMargin = 1 &lt;&lt; 5
  };
  typedef NSUInteger UIViewAutoresizing;
  
  </code>
  </pre>
  
  <p><strong>Edit:</strong> Alright so I now understand how and why you would use the left bit-shift, my next question is how would I test to see if the the value had a certain trait using and if/then statement or a switch/case method?</p>