ile error f() is not const 
... 
ar &lt;&lt; x 
</pre></code>
  <p>
  He's mildly annoyed now he tries the following: 
  <ul>
    <li>He considers making f() a const - but presumable that shifts the const 
    error to somewhere else. And his doesn't want to fiddle with "his" code to 
    work around a quirk in the serializaition system 
    <p>
    <li>He removes the <code style="white-space: normal">const</code>
    from <code style="white-space: normal">const construct_from</code> above - damn now he 
  