title: When "this" is captured by a lambda, does it have to be used explicitly?
body: <p>The examples I have found that capture <code>this</code> in a lambda use it explicitly; e.g.:</p>
  
  <pre><code>capturecomplete = [this](){this-&gt;calstage1done();};
  </code></pre>
  
  <p>But it seems it is also possible to use it implicitly; e.g.:</p>
  
  <pre><code>capturecomplete = [this](){calstage1done();};
  </code></pre>
  
  <p>I tested this in g++, and it compiled.</p>
  
  <p>Is this standard C++? (and if so, which version), or is it some form of extension?</p>