C++ 함수 및 포인터

double pam(int); //参数为int 类型，返回值为double 类型的函数
double (*pf);(int)  //指向参数为int类型,返回值为double 类型的指针
pf = pam;   //函数名代表了函数的地址

double x = pam(4); //函数名调用
double x = (*pf)(4); //指针调用
double x = pf(4); //C++也允许将指针名当作函数名使用

 const double * f1(const double *, int);
 const double * (*p1)(const double *, int); //p1 poitns to f1
 auto p2 = f1; //C++11 automatic type deduction,p2 points to f1 as well

//前面函数为double *类型，cout第一部分返回double指针，第二部分返回double指针指向的值
cout<<(*p1)(av,3)<<":"<<*(*p1)(av,3)<<endl;
//和上面的cout一样只不过是使用函数指针名来调用函数
cout<<p2(av,3)<<":"<<*p2(av,3)<<endl;

const double *(*pa[3]) (const double *,int) = {f1,f2,f3}; //创建函数指针数组
//通过指针调用函数，得到返回的指针
const double *px = pa[0](av,3); //call by pointer as if it were a function name
const double *py = (*pa[0])(av,3); //正常调用

//得到函数返回指针指向的值
double x = *pa[0](av,3);
double x = *(*pa[0])(av,3);

*pd[3] //an array of 3 pointers
(*pd)[3] //a pointer to an array of three elements