虚函数与重载函数的关系
1.普通的函数重载是，函数的参数或参数类型必须先有所不同，返回类型也可不同。
2.虚函数重载时，要求函数名，返回类型，参数个数，参数类型，顺序都要与基类函数原型完全相同
a..当返回类型不相同，其他完全相同，则报错
b.函数名相同，而参数个数，参数类型，顺序不同，系统视为普通重载，失去虚函数特性
#include<iostream>using namespace std;class Base{public:virtual void f1();virtual void f2();virtual void f3();void f4();};class Deriverd:public Base{public:virtual void f1();//是虚函数，这里的virtual可以不写void f2(int x); //与Base的f2()作为普通函数重载，虚特性消失//char void f3(); //错，与基类的返回类型不同void f4();};void Base::f1(){cout<<"base f1()"<<endl;}void Base::f2(){cout<<"base f2()"<<endl;}void Base::f3(){cout<<"base f3()"<<endl;}void Base::f4(){cout<<"base f4()"<<endl;}void Deriverd::f1(){cout <<"Deriverd f1()"<<endl;}void Deriverd::f2(int x){cout <<"Deriverd f2(int x)"<<endl;}//void Deriverd::f3()//{//cout<<"Deriverd f3()"<<endl;//}void Deriverd::f4(){cout <<"Deriverd f4()"<<endl;}int main(){Base b,*bp;Deriverd d;bp=&d;bp->f1();bp->f2();bp->f3();bp->f4();return 0;}