title: stl priority_queue of C++ with struct
body: <p>How can we use STL <code>priority_queue</code> for struct ?
  Any <strong>illustration</strong> of pushing &amp; popping , where struct has multiple data-types? <br>
  Say : <code>struct thing { int a; char b;} glass[10];</code> .<br>Now how can i put this struct on priority_queue using 'int a' for ordering ?</p>