title: What does the "operator()..." syntax mean in C++?
body: <p>I'm trying to understand the example of <code>std::visit</code> from <a href="http://en.cppreference.com/w/cpp/utility/variant/visit" rel="noreferrer">cppreference</a>, Where I saw the following line of code:</p>
  
  <pre><code>template&lt;class... Ts&gt; struct overloaded : Ts... { using Ts::operator()...; };
  template&lt;class... Ts&gt; overloaded(Ts...) -&gt; overloaded&lt;Ts...&gt;;
  </code></pre>
  
  <p>I don't understand. What does <code>operator()...</code> mean in the code? </p>