title: Convert a string to a unsigned long long in c++
body: <p>Convert a string to a unsigned long long.</p>
  
  <pre><code>string str = "0x1232"
  </code></pre>
  
  <p>How do I convert to a unsigned long long.</p>
  
  <p>This is what i've tried.</p>
  
  <pre><code>unsigned long long ull;
  ull = stoull(str, NULL, 0);
  </code></pre>
  
  <p>Error:</p>
  
  <pre><code> error: identifier "stoull" is undefined
                          ull = stoull(str, NULL, 0);
  </code></pre>
  
  <p>Can you give me some pointers?</p>