title: Difference between c++ string append and operator +=
body: <p>Is there any noticeable difference between the two lines? My coworker says that using += is "faster" but I don't see why they should be any different:</p>
  
  <pre><code>string s1 = "hello";
  string s2 = " world";
  
  // Option 1
  s1 += s2;
  
  // Option 2
  s1.append(s2);
  </code></pre>
  
  <p>To clarify, I am not asking about the <strong>usage differences</strong> between the two functions - I am aware that <code>append()</code> can be used for a wider variety of uses and that <code>operator +=</code> is somewhat more specialized. What I care about is how this particular example gets treated.</p>