If you need the function to be called on a particular object, add that object before the ::.

In this snippet, lessThanZero() is a member function of Thingy, but hasMatch() is a top-level function. If we want to use lessThanZero(), we not only need the function, but a Thingy instance on which to call that function. So, we create such an instance (thingy) and use that along with the rest of the function reference (thingy::lessThanZero()).

You can learn more about this in:
Run Edit