c++ – Function Template Refinement

Question:

Clear sky!

I'm reading a C++ tutorial. There's an example of class template refinement:

template<typename T> class MyCout
{
    private:
        T data;
    public:
        MyCout(T a): data(a) {};
        void display() {cout << data << endl;};
};

template<> class MyCout<string>
{
    private:
        string data;
    public:
        MyCout(string a): data(a){};
        void display() {cout << data.c_str() << endl;};
};

I decided to experiment and shorten the code a little, making the template not of the whole class, but only of the function:

class NewCout
{
    public:
        NewCout(){};
        template<typename T> void display(T a){cout << a << endl;};
        template<> void display<string>(string a){cout << a.c_str() << endl;};
};

But the compiler throws an error on line #6: invalid explicit specialization before '>' token .
What am I doing wrong?

---

And one more question in pursuit: how is it customary to design templates?

Answer:

C++ forbids partial specialization of methods, only class templates can be specialized. See the standard , paragraph 14.5.6. Why this was done is discussed here (warning: English langwidge inside!).

Apparently, the author of the book is wrong.

You can, however, override the template method (which is not the same).

---

Oh, shame on me. Here it works:

class C
{
public:
    template<typename T>
    void f(T t);
};

template<typename T>
void C::f(T t)
{
    cout << t << endl;
}

template<>
void C::f<int>(int t)
{
    cout << "(int specialization) " << t << endl;
}

---

Understood. In the example above the line, not partial , but full specialization. Partial specialization is still prohibited, as the spec says. Example :

class C
{
public:
    template<typename T>
    void f(T t);
};

template<typename T>
void C::f(T t)
{
    cout << t << endl;
}

template<typename T> // ошибка: function template partial 
void C::f<T*>(T* pt) // specialization ‘f<T*>’ is not allowed
{
    cout << "(pointer specialization) " << *pt << endl;
}