title: Why can't I pass a bound member function as a callable?
body: <p>This code is a compile error:</p>
  
  <pre><code>std::string str("hello world"); 
  std::unordered_set filter{'h', 'w', ' '};
  str.erase(std::remove_if(str.begin(), str.end(), filter.count), str.end());
  </code></pre>
  
  <p>I know this can be done with a lambda, but why is it not allowed like this? Works fine in Java.</p>