title: How to concatenate/merge vectors
body: <p>I'm trying to figure out a way to merge 2 vectors and an integer into one vector. ie</p>
  
  <pre><code>return data.push_back(fn(data1), mid, fn(data2));
  </code></pre>
  
  <p>NB This is a recursive function.  The vector data has values stored in it before it reaches the return statement.  I need the values in data to be updated with the values in the return statement.</p>
  
  <p>I have absolutely no idea how to go about doing this.  I've been searching for a couple of hours, but nothing seems to work!</p>
  
  <p>Any guidance is very much appreciated.</p>