Error while Executing template Code

[Pallav singh]

Hi

can any one provide solution for it

Thanks
Pallav

---------------------------------------------------------------------------------------------------------------------------

template<typename T>
class BXT {
public:
typedef T Mystery;
template<typename U>
struct Magic;
};

template<typename T>
class DXTT : private BXT<T> {
public:

typename BXT<T>::Mystery * p;
template BXT<T>::template Magic<U> * plink;
// I am getting at this Line
// can anyone suggest Soltuion for it

};

 

[Victor Bazarov]

Hi

can any one provide solution for it

Thanks
Pallav

---------------------------------------------------------------------------------------------------------------------------

template<typename T>
class BXT {
public:
typedef T Mystery;
template<typename U>
struct Magic;
};

template<typename T>
class DXTT : private BXT<T> {
public:

typename BXT<T>::Mystery * p;

template BXT<T>::template Magic<U> * plink;

There is no 'U' in the context of this (DXTT) class. What is
'plink' supposed to be? A pointer to what? Since the type
'BXT<T>::Magic' is not really a type, but a *template*, you
cannot declare a pointer to it. You have to instantiate it
first. In your case 'Magic' needs the list of arguments, and
it should have only one element. What is it supposed to be?

If the argument for 'Magic' is, for instance, 'int', then the
declaration of 'plink' would be

typename BXT<T>::Magic<int> * plink;

But you have given _no_ indication what you want to use as the
argument for 'Magic' template. Perhaps your 'DXTT' template
needs to have two arguments, 'T' and 'U'?

// I am getting at this Line
// can anyone suggest Soltuion for it

};

V

 

[Andrey Tarasevich]

template<typename T>
class BXT {
public:
typedef T Mystery;
template<typename U>
struct Magic;
};

template<typename T>
class DXTT : private BXT<T> {
public:
typename BXT<T>::Mystery * p;
template BXT<T>::template Magic<U> * plink;

Firstly, as Victor said already, there's no 'U' in this context.
Secondly, it is supposed to be

typename BXT<T>::template Magic<...whatever...>* plink;
^^^^^^^^
Note the first keyword: 'typename', not 'template'.