C++虚函数与默认参数

 1 class Base {
 2 public:
 3     virtual void disp(int x = 3) {//虚函数带默认参数值，3
 4        cout << "Base::x is " << x << endl;
 5     }
 6 };
 7 class Derived: public Base {
 8 public:
 9     virtual void disp(int x = 100) {//子类重定义了默认参数值,100
10         cout << "Derived::x is " << x << endl;
11     }
12 };
13 ?
14 Base* ins = new Derived();
15 ins->disp();