函数指针也可作为函数的参数

#include <iostream>
using namespace std;
void square(float&x,float&y){x=x*x;y=y*y;}
void cube(float&x,float&y){x=x*x*x;y=y*y*y;}
void print(void (*p)(float&,float&),float&x,float&y)
{
cout<<"执行函数前:"<<endl;
cout<<"x:"<<x<<"/ty:"<<y<<endl;
p(x,y);
cout<<"执行函数后:"<<endl;
cout<<"x:"<<x<<"/ty:"<<y<<endl;
}
void Swap(float&x,float&y){int z;z=x;x=y;y=z;}
int main()
{
float a=2,b=3;
char choice='0';
int i;
void (*p[5])(float&x,float&y);
for (i=0;i<5;i++)
{
cout<<"[0]退出[1]平方[2]立方[3]交换x和y的值:";
cin>>choice;
bool quit=false;
switch (choice)
{
case '0':quit=true;break;
case '1':p[i]=square;break;
case '2':p[i]=cube;break;
case '3':p[i]=Swap;break;
default:p[i]=0;
}
if (quit==true){break;}
if (p[i]==0){cout<<"请输入一个从0到3之间的数字!"<<endl;i=i-1;continue;}
print(p[i],a,b);
}
return 0;
}