Template is powerful in C++, you can do all sort of crazy thing

template 
T fun(T a, T b){
    return a + b;
}
// You can use default argument too
template < typename T = int > 
T fun(T a, T b = 0){
    return a + b;
}

C++ class template

template < class T=int >
class MyClass{ 
    public:
        MyClass(T a, T b=0){
        }
};