c++mooc第六章小测

（红色为补充代码）

001:看上去像多态

#include <iostream>
using namespace std;
class B { 
    private: 
        int nBVal; 
    public: 
        void Print() 
        { cout << "nBVal="<< nBVal << endl; } 
        void Fun() 
        {cout << "B::Fun" << endl; } 
        B ( int n ) { nBVal = n;} 
};
//补充代码
class D:public B
{
private:
    int nDVal;
public:
    D(int nDval_) :nDVal(nDval_),B(3*nDval_){};

    void Fun()
    {
        cout << "D::Fun" << endl;
    }

    void Print()
    {
        B::Print();
        cout << "nDVal=" << nDVal << endl;
    }

};

int main() { 
    B * pb; D * pd; 
    D d(4); d.Fun(); 
    pb = new B(2); pd = new D(8); 
    pb -> Fun(); pd->Fun(); 
    pb->Print (); pd->Print (); 
    pb = & d; pb->Fun(); 
    pb->Print(); 
    return 0;
}

002:Fun和Do：

#include <iostream> 
using namespace std;
class A { 
    private: 
    int nVal; 
    public: 
    void Fun() 
    { cout << "A::Fun" << endl; }; 
    void Do() 
    { cout << "A::Do" << endl; } 
}; 
class B:public A { 
    public: 
    virtual void Do() 
    { cout << "B::Do" << endl;} 
}; 
class C:public B { 
    public: 
    void Do( ) 
    { cout <<"C::Do"<<endl; } 
    void Fun() 
    { cout << "C::Fun" << endl; } 
}; 
void Call(
//补充代码
B &p
) { 
    p.Fun(); p.Do(); 
} 
int main() { 
    C c; 
    Call( c); 
    return 0;
}

003:这是什么鬼delete

#include <iostream> 
using namespace std;
class A 
{ 
public:
    A() { }
//补充代码
virtual ~A(){
    cout<<"destructor A"<<endl;
}
}; 
class B:public A { 
    public: 
    ~B() { cout << "destructor B" << endl; } 
}; 
int main() 
{ 
    A * pa; 
    pa = new B; 
    delete pa; 
    return 0;
}

004:怎么又是Fun和Do

#include <iostream>
using namespace std;
class A {
    private:
    int nVal;
    public:
    void Fun()
    { cout << "A::Fun" << endl; };
    virtual void Do()
    { cout << "A::Do" << endl; }
};
class B:public A {
    public:
    virtual void Do()
    { cout << "B::Do" << endl;}
};
class C:public B {
    public:
    void Do( )
    { cout <<"C::Do"<<endl; }
    void Fun()
    { cout << "C::Fun" << endl; }
};
void Call(
//补充代码
A*p
) {
    p->Fun(); p->Do();
}
int main() {
    Call( new A());
    Call( new C());
    return 0;
}