title: Auto deduced return types in forward declaration and mixing with old function syntax
body: <h2>Intro</h2>
  
  <p>In C++11 it's fine to declare a function like</p>
  
  <pre><code>auto times2(double num) -&gt; double; // A
  </code></pre>
  
  <p>and define it like </p>
  
  <pre><code>double times2(double num) { // B
      return num*2;
  }
  </code></pre>
  
  <p>The pair <code>A, B</code> can also be mixed the other way around. </p>
  
  <p>C++14 introduces a third way </p>
  
  <pre><code>auto times2(double num) { // C
      return num;
  }
  </code></pre>
  
  <h2>Q</h2>
  
  <ol>
  <li>Can style <code>C</code> be <strong>mixed</strong> with <code>A / B</code> in a <strong>declaration/definition</strong> pair ?</li>
  <li><p>Can <code>C</code> <strong>stand alone as a signature</strong> (when the body of the function is not yet provided) ? </p>
  
  <pre><code>// waiting for the definition to provide info on return type
  auto times2(double); 
  </code></pre></li>
  </ol>