/* 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. */template<typename T>class IsFunctionT {  private:    typedef char One;    typedef struct { char a[2]; } Two;    template<typename U> static One test(...);    template<typename U> static Two test(U (*)[1]);  public:    enum { Yes = sizeof(IsFunctionT<T>::test<T>(0)) == 1 };    enum { No = !Yes };};template<typename T>class IsFunctionT<T&> {  public:    enum { Yes = 0 };    enum { No = !Yes };};template<>class IsFunctionT<void> {  public:    enum { Yes = 0 };    enum { No = !Yes };};template<>class IsFunctionT<void const> {  public:    enum { Yes = 0 };    enum { No = !Yes };};// same for void volatile and void const volatile//...template<typename T>class CompoundT {           // primary template  public:    enum { IsPtrT = 0, IsRefT = 0, IsArrayT = 0,           IsFuncT = IsFunctionT<T>::Yes,           IsPtrMemT = 0 };    typedef T BaseT;    typedef T BottomT;    typedef CompoundT<void> ClassT;};