[FIXED] How to initialize static members of two various types of template class

Issue

I want to assign two different values to A<int> and A<char>,then each kind of instantialized classes have their own static member 'a',but the program compile failed.

Here's the code.

#include <iostream>
using namespace std;
template<class T>
class A {
private:
    static int a;
public:
    friend ostream& operator<<<T>(ostream& os, A<T>& p); 
};
template<class T>
ostream& operator<<(ostream& os, A<T>& p){
    cout << p.a;
    return os;
}
template<class T>int A<T>::a = 5;
template<class T>char A<T>::a = 50;//error:the declaration is not compatible with the previous "int A<T>::A"declaration
int main()
{
    A<int> v1, v2, v3;
    A<char>v11, v22, v33;
    cout << v1<<" "<<v2<<" "<<v3<<endl;

}

So what should I do?

Solution

You need to do an explicit specialization which you do by writing an empty template declaration and replacing T in A<T> with the type you want.

template<> int A<int>::a = 5;
template<> int A<char>::a = 50;

Answered By - David G

Answer Checked By - Willingham (PHPFixing Volunteer)