title: c++ math/hex question
body: <p>Sorry if this sounds a bit 'noobish' but I don't know c++ and I was looking at some code for the perlin noise, trying to figure it out when I came across</p>
  
  <p><code>&amp; 0x7fffffff</code></p>
  
  <p>and</p>
  
  <p><code>(n &lt;&lt; 13) ^ n;</code></p>
  
  <p>and I have no idea what those mean. I do know that <code>0x7fffffff</code> is hex, but I don't know what the <code>&amp;</code> means <em>Any help?</em></p>