title: C++ auto conversions
body: <p>For two unrelated classes "class A" and "class B"
  and a function </p>
  
  <pre><code>B convert(const A&amp;);
  </code></pre>
  
  <p>Is there a way to tell C++ to automatically, for any function that takes "class B" as argument, to auto convert a "class A".</p>
  
  <p>Thanks!</p>