template<typename Base, int D>¶

class kdb::Discriminator< Base, D >" This technique with the PolicySelector and Discriminator is taken from the book 'C++ Templates - The Complete Guide' by David Vandevoorde and Nicolai M.

Josuttis, Addison-Wesley, 2002 in Chapter 16 Templates and Inheritance: Named Template Arguments

The technique allows users of the class Value to use any number and order of policies as desired.