/* 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. */#ifndef FORWARD_HPP#define FORWARD_HPP#include "ifthenelse.hpp"#include "typet.hpp"#include "typeop.hpp"// ForwardParamT<T>::Type is// - constant reference for class types// - plain type for almost all other types// - a dummy type (Unused) for type voidtemplate<typename T>class ForwardParamT {  public:    typedef typename IfThenElse<TypeT<T>::IsClassT,                                 typename TypeOp<T>::RefConstT,                                 typename TypeOp<T>::ArgT                               >::ResultT            Type;};template<>class ForwardParamT<void> {  private:    class Unused {};  public:    typedef Unused Type;};#endif // FORWARD_HPP