/* The following code example is taken from the book * "C++ Templates - The Complete Guide" * by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002 * * (C) Copyright David Vandevoorde and Nicolai M. Josuttis 2002. * Permission to copy, use, modify, sell and distribute this software * is granted provided this copyright notice appears in all copies. * This software is provided "as is" without express or implied * warranty, and with no claim as to its suitability for any purpose. */// primary template handles maximum number of parameters:template<typename RT, typename P1 = void,                       typename P2 = void,                      typename P3 = void>class FunctionPtrT {  public:    enum { NumParams = 3 };    typedef RT (*Type)(P1,P2,P3);};// partial specialization for two parameters:template<typename RT, typename P1,                      typename P2>class FunctionPtrT<RT, P1, P2, void> {  public:    enum { NumParams = 2 };    typedef RT (*Type)(P1,P2);};// partial specialization for one parameter:template<typename RT, typename P1>class FunctionPtrT<RT, P1, void, void> {  public:    enum { NumParams = 1 };    typedef RT (*Type)(P1);};// partial specialization for no parameters:template<typename RT>class FunctionPtrT<RT, void, void, void> {  public:    enum { NumParams = 0 };    typedef RT (*Type)();};