title: How to initialize a private static set in c++?
body: <p>I have a private set member with the following header declaration</p>
  
  <pre><code>class foo
  {
      private:
          static std::set&lt;int&gt; _mySet;
  };
  </code></pre>
  
  <p>How can I use _mySet in my source file? I have tried to initialize it but these didn't work:</p>
  
  <pre><code>std::set&lt;int&gt; foo::_mySet{};  //  error: qualified-id in declaration before ‘{’ token
  foo::_mySet = std::set&lt;int&gt;();  // error "...is private within this context"
  </code></pre>