title: Is it possible to access (read only) the variables captured by a lambda?
body: <p>Is it possible to access (read only) the variables captured by a lambda?</p>
  
  <p>This doesn't work:</p>
  
  <pre><code>std::function&lt;double  (const double)&gt; plus (const double a) {
      return [a] (const double b) -&gt; double {
          return a+b;
      };
  }
  
  auto plus5 = plus(5);
  cout &lt;&lt; plus5.a &lt;&lt; endl;
  </code></pre>