C++普通类从模板类派生

#include<iostream>
using namespace std;
/*欲得到模板类,就必须定义一个类模板,然后从才能从类模板按需求实例化出某个模板类*/
template<class T>
class A
{
  T v1;
public:
  void print()
  {
    cout << "v1=" << v1 << endl;
  }
};

/*普通类B 从 模板类A<int> 派生*/
class B :public A<int>//模板类A<int>
{
  int a;
public:
  B(int a_ = 0) :a(a_) { cout << "constructor was called !" << endl; }
  void set(int a_)
  {
    a = a_;
  }
  void print()
  {
    cout << "a=" << a << endl;
  }
};
int main()
{
  B obj(5);
  obj.print();
  obj.set(7);
  obj.print();
}