The following code example is taken from the book
C++ Templates - The Complete Guide
by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002
© Copyright David Vandevoorde and Nicolai M. Josuttis 2002
#include "typeop.hpp"
template <typename T>
void apply (typename TypeOp<T>::RefT arg, void (*func)(T))
{
func(arg);
}