C++从模板类派生出类模板

#include<iostream>
using namespace std;
//从模板类派生出类模板
/*类模板A*/
template <class T1 ,class T2 >
class A
{
protected:
  T1 v1;
  T2 v2;
public:
  void print()
  {
    cout << "v1=" << v1 << endl;
    cout << "v2=" << v2 << endl;
  }
  void setA(T1 v1_,T2 v2_)
  {
    v1 = v1_; v2 = v2_;
  }
};

template<class T>
class B :public A<int, double>//A<int,double>是具体的模板类;类模板B从基类A<int,double>共有派生而来
{
  /*此前从A<int,double>基类继承过来所有成员*/
  T v;
public:
  void print()
  {
    cout << "v=" << v << endl;
  }

  void setB(T v_)
  {
    v = v_;
  }
};
int main()
{
  B<char> obj;
  /*此时编译器已经生成两个模板类:B<char>和它的基类A<int,double>*/
  obj.setA(7, 7.77);
  obj.setB('N');
  obj.A<int, double>::print();
  obj.print();
  return 0;
}