That's the syntax for describing a lambda function. CPP reference has a nice overview of it: http://en.cppreference.com/w/cpp/language/lambda http://en.cpprefe

That's the syntax for describing a lambda function. CPP reference has a nice overview of it: http://en.cppreference.com/w/cpp/language/lambda http://en.cppreference.com/w/cpp/language/lambda