1. As with any other global scope definitions, a class template definition can be placed in a namespace.
  2. The class template name MyClass must be qualified by the namespace name ns when it is used outside of the namespace, or be introduced through a using declaration. 
     #include <iostream>
    
 namespace ns {
    
    template<class T1, class T2>
    class MyClass {
    public:
       MyClass(T1 m1, T2 m2) : _m1(m1), _m2(m2) {}
       void show(){
          std::cout << "m1 = "<< _m1 << ", m2 = " << _m2 << std::endl;
       };
    private:
       T1 _m1;
       T2 _m2;
    };
    
 }
    
 int main(){
    
    ns::MyClass<int, float> obj(2, -2.64f);
    obj.show();
    
    return 0;
 }
  3. When this pointer is used to refer to the member function show(), it refers to the member function show() of this template instantiation. 
    #include <iostream>
   
namespace ns {
   template<class T1, class T2>
   class MyClass {
   public:
      MyClass(T1 m1, T2 m2) : _m1(m1), _m2(m2) {}
      void show(){
         std::cout << "m1 = "<< _m1 << ", m2 = " << _m2 << std::endl;
      };
   private:
      T1 _m1;
      T2 _m2;
   };
}
   
int main(){
   
   ns::MyClass<int, float>* p_obj = new ns::MyClass<int,float>(2, -2.64f);
   p_obj->show();
   delete p_obj;
   
   return 0;
}
  4. A specialization declaration for a class template or for a member of a class template must be declared in the namespace where the generic template is defined. 
     #include <iostream>
    
 namespace ns {
    template<class T1, class T2>
    class MyClass {
    public:
       MyClass(T1 m1, T2 m2) : _m1(m1), _m2(m2) {}
       void show(){
          std::cout << "Called ns::MyClass<int,float>::show()\n";
          std::cout << "m1 = "<< _m1 << ", m2 = " << _m2 << std::endl;
       };
    private:
       T1 _m1;
       T2 _m2;
    };
    
    // partial specialization declaration for ns::MyClass<float, T>
    template<class T> class MyClass<float, T>;
    
    // specialization declaration for ns::MyClass<float, char>
    template<> class MyClass<float, char>;
    
    // specialization declaration for ns::MyClass<double,double>::show()
    template<> void MyClass<double, double>::show();
    
 }
    
 // partial specialization definition for ns::MyClass<float, T>
 template<class T>
 class ns::MyClass<float, T> {
    public:
       MyClass(float m1, T m2) : _m1(m1), _m2(m2) {}
       void show(){
          std::cout << "Called ns::MyClass<float,T>::show()\n";
          std::cout << "m1 = "<< _m1 << ", m2 = " << _m2 << std::endl;
       };
    private:
       float _m1;
       T   _m2;
 };
    
 // specialization definition for ns::MyClass<float, char>
 template<>
 class ns::MyClass<float, int> {
    public:
       MyClass(float m1, int m2) : _m1(m1), _m2(m2) {}
       void show(){
          std::cout << "Called ns::MyClass<float,int>::show()\n";
          std::cout << "m1 = "<< _m1 << ", m2 = " << _m2 << std::endl;
       };
    private:
       float _m1;
       int   _m2;
 };
    
    
 // specialization definition for ns::MyClass<double,double>::show()
 template<>
 void ns::MyClass<double, double>::show(){
    std::cout << "Called ns::MyClass<double,double> show()\n";
    std::cout << "m1 = "<< _m1 << ", m2 = " << _m2 << std::endl;
 }
    
 int main(){
    
    ns::MyClass<int, float>* p_obj1 = new ns::MyClass<int,float>(2, -2.64f);
    p_obj1->show();
    delete p_obj1;
    
    ns::MyClass<float, int>* p_obj2 = new ns::MyClass<float,int>(26.502f, -2);
    p_obj2->show();
    delete p_obj2;
    
    ns::MyClass<double,double>* p_obj3 = new ns::MyClass<double, double>(2.6e-3, -2.51);
    p_obj3->show();
    delete p_obj3;
    
    ns::MyClass<float, double>* p_obj4 = new ns::MyClass<float,double>(26.502f, -2.55);
    p_obj4->show();
    delete p_obj4;
    
    return 0;
 }