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;
}