C++函数指针详解

double cal(int);   // prototype
double (*pf)(int);   // 指针pf指向的函数， 输入参数为int,返回值为double 
pf = cal;    // 指针赋值

void estimate(int lines, double (*pf)(int));  // 函数指针作为参数传递

double y = cal(5);   // 通过函数调用
double y = (*pf)(5);   // 通过指针调用 推荐的写法 
double y = pf(5);     // 这样也对， 但是不推荐这样写

#include <iOStream>
#include <alGorithm>
#include <cmath>
 
using namespace std;
 
double cal_m1(int lines)
{
	return 0.05 * lines;
} 
 
double cal_m2(int lines)
{
	return 0.5 * lines;
}
 
void estimate(int line_num, double (*pf)(int lines))
{
	cout << "The " << line_num << " need time is: " << (*pf)(line_num) << endl; 
}
 
 
 
int main(int arGC, char *argv[])
{
	int line_num = 10;
	// 函数名就是指针，直接传入函数名
	estimate(line_num, cal_m1);
	estimate(line_num, cal_m2); 
	return 0;
}

#include <iostream>
#include <algorithm>
#include <cmath>
 
using namespace std;
 
// prototype   实质上三个函数的参数列表是等价的 
const double* f1(const double arr[], int n);
const double* f2(const double [], int);
const double* f3(const double* , int);
 
 
 
int main(int argc, char *argv[])
{
	double a[3] = {12.1, 3.4, 4.5};
	
	// 声明指针
	const double* (*p1)(const double*, int) = f1;
	cout << "Pointer 1 : " << p1(a, 3) << " : " << *(p1(a, 3)) << endl;
	cout << "Pointer 1 : " << (*p1)(a, 3) << " : " << *((*p1)(a, 3)) << endl;
	
	const double* (*parray[3])(const double *, int) = {f1, f2, f3};   // 声明一个指针数组，存储三个函数的地址 
	cout << "Pointer array : " << parray[2](a, 3) << " : " << *(parray[2](a, 3)) << endl;
	cout << "Pointer array : " << parray[2](a, 3) << " : " << *(parray[2](a, 3)) << endl;
    cout << "Pointer array : " << (*parray[2])(a, 3) << " : " << *((*parray[2])(a, 3)) << endl;
    
	return 0;
}
 
 
const double* f1(const double arr[], int n)
{
	return arr;     // 首地址 
} 
 
const double* f2(const double arr[], int n)
{
	return arr+1;
}
 
const double* f3(const double* arr, int n)
{
	return arr+2;
}

typedef const double* (*pf)(const double [], int);  // 将pf定义为一个类型名称；
pf p1 = f1;
pf p2 = f2;
pf p3 = f3;