第十三周项目一（二）

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2、显然，Animal设计为抽象类更合适，Animal不需要能够实例化，是专门作基类使用的。改造程序，使Animal设计为抽象类，这时main()函数中p = new Animal();将出错，将此行删除。

#include <iostream>using namespace std;class Animal{public:  virtual void cry()=0;};class Mouse: public Animal{public:    Mouse(string nam,char s):name(nam),sex(s){}    virtual void cry();protected:    string name;    char sex;};void Mouse::cry(){    cout<<"我叫"<<name<<",";    if(sex=='m')        cout<<"我是一只男老鼠,";    else cout<<"我是一只女老鼠,";    cout<<"我的叫声是：吱吱吱！"<<endl;}class Cat: public Animal{public:    Cat(string nam):name(nam){};    virtual void cry();protected:    string name;};void Cat::cry(){    cout<<"我叫："<<name<<",是一只猫，我的叫声是：喵喵喵！"<<endl;}class Dog: public Animal{public:    Dog(string nam):name(nam){};    virtual void cry();protected:    string name;};void Dog::cry(){    cout<<"我叫："<<name<<",是一只狗，我的叫声是：汪汪汪！"<<endl;}class Giraffe :public Animal{public:    Giraffe(string nam,char s):name(nam),sex(s){};    virtual void cry();protected:    string name;    char sex;};void Giraffe::cry(){    cout<<"我叫："<<name<<",是"<<((sex=='m')?"男":"女")<<"长颈鹿，我的脖子太长，发不出声音来！"<<endl;}int main( ){    Animal *p;    //p = new Animal();    //p->cry();    Mouse m1("Jerry",'m');    p=&m1;    p->cry();    Mouse m2("Jemmy",'f');    p=&m2;    p->cry();    Cat c1("Tom");    p=&c1;    p->cry();    Dog d1("Droopy");    p=&d1;    p->cry();    Giraffe g1("Gill",'m');    p=&g1;    p->cry();    return 0;}

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