title: struct in a struct in C++
body: <p>I need help to understand well the use of <code>struct</code></p>
  
  <p>I have this snippet of code:</p>
  
  <pre><code>struct PCD
  {
      PointCloud::Ptr cloud;
      std::string f_name;
      PCD() : cloud (new PointCloud) {};
  };
  </code></pre>
  
  <p>But I don't understand how is possible this row:</p>
  
  <pre><code>PCD() : cloud (new PointCloud) {};
  </code></pre>
  
  <p>or better, what does it do? A <code>struct</code> in the <code>struct</code>?</p>
  
  <p>Where could I find a good explanation of it?</p>