title: In C++11, what is the point of a thread which "does not represent a thread of execution"?
body: <p>Looking over the new threading stuff in C++11 to see how easily it maps to pthreads, I notice the curious section in the <code>thread</code> constructor area:</p>
  
  <blockquote>
    <p><strong>thread();</strong><br>
    <em>Effects:</em> Constructs a thread object that does not represent a thread of execution.<br>
    <em>Postcondition:</em> get_id() == id()<br>
    <em>Throws:</em> Nothing.<br></p>
  </blockquote>
  
  <p>In other words, the default constructor for a thread doesn't actually seem to <em>create</em> a thread. Obviously, it creates a thread <em>object,</em> but how exactly is that useful if there's no backing code for it? Is there some other way that a "thread of execution" can be attached to that object, like <code>thrd.start()</code> or something similar?</p>