函数指针与指针函数

#include <iostream>
const double * f1(const double ar[],int);
const double * f2(const double [],int);
const double * f3(const double *,int);
int main(){
using namespace std;
double av[3]={1112.3,1542.6,2227.6};
//指针函数
const double* (*p1)(const double *,int)=f1;//一个指向函数的指针，其中这个函数返回const double*类型，参数是const double *
auto p2=f2;//两个等价
cout<<"using pointers to fuctions:\n";
cout<<"address value\n";
cout<<(*p1)(av,3)<<":"<<*(*p1)(av,3)<<endl;
cout<<p2(av,3)<<":"<<*p2(av,3)<<endl;

//函数指针数组的指针
const double* (*pa[3])(const double [],int)={f1,f2,f3};
cout<<"\nUsing an array of pointers\n";
cout<<"address value\n";
for (int i=0; i<3; i++) {
cout<<pa[i](av,3)<<":"<<*pa[i](av,3)<<endl;
}
//指向函数指针的指针
cout<<"\nUsing a pointer to pointers\n";
cout<<"address value\n";
for (int i=0; i<3; i++) {
cout<<pa[i](av,3)<<":"<<*pa[i](av,3)<<endl;
//一个指向函数指针数组的指针
cout<<"\nUsing a pointer to array of pointers\n";
cout<<"address value\n";
//auto pc=&pa;
const double * (*(*pc)[3])(const double [],int)=&pa;
for (int i=0; i<3; i++)
cout<<(*pc)[i](av,3)<<":"<<*((*pc)[i](av,3))<<endl;

}
}

const double * f1(const double ar[],int n){
return ar;
}
const double * f2(const double ar[],int){
return ar+1;
}
const double * f3(const double *ar,int){
return ar+2;
}