title: User-defined Literals suffix, with *_digit..."?
body: <p>A <strong>user-defined literal suffix</strong> in C++0x should be an <strong>identifier</strong> that</p>
  
  <ul>
  <li>starts with <code>_</code> (underscore) (17.6.4.3.5)</li>
  <li>should <em>not</em> begin with <code>_</code> followed by uppercase letter (17.6.4.3.2)
  <blockquote>
    <p>Each name that [...] begins with an underscore followed by an uppercase letter is reserved to the implementation for any use.</li>
    </ul>
  
  <p>Is there any reason, why such a suffix may not start <code>_</code> <strong>followed by a digit</strong>? I.E. <code>_4</code> or <code>_3musketeers</code>?</p>
  </blockquote></p>
  
  <pre><code>Musketeer dartagnan = "d'Artagnan"_3musketeers;
  int num = 123123_4; // to be interpreted in base4 system?
  string s = "gdDadndJdOhsl2"_64; // base64decoder
  </code></pre>