# 学点 C 语言(38): 函数 - 函数指针

2014/09/26 15:32

``````//这是一个求和函数的定义:
{
return(x + y);
}

//可以这样声明:

//也可以这样声明:

``````

``````//像这样:
int (*pfun)(int, int);

//或这样:
int (*pfun)(int x, int y);

//也可以:
typedef int (*pfun)(int, int);

//这就声明了一个叫 pfun 的函数指针, 能被它指向的函数一定要有相同的参数格式.

``````

1. 简单例子:
``````#include <stdio.h>

int add(int x, int y) {return(x + y);}
int sub(int x, int y) {return(x - y);}
int mul(int x, int y) {return(x * y);}
int div(int x, int y) {return(x / y);}

int main(void)
{
int (*pf)(int, int);

printf("%d\n", pf(9, 3)); /* 12 */

pf = sub;
printf("%d\n", pf(9, 3)); /* 6  */

pf = mul;
printf("%d\n", pf(9, 3)); /* 27 */

pf = div;
printf("%d\n", pf(9, 3)); /* 3  */

getchar();
return 0;
}

``````

2. 函数指针数组:
``````#include <stdio.h>

int add(int x, int y) {return(x + y);}
int sub(int x, int y) {return(x - y);}
int mul(int x, int y) {return(x * y);}
int div(int x, int y) {return(x / y);}

int main(void)
{
int (*pf[4])(int, int) = {add, sub, mul, div};

printf("%d\n", pf[0](9, 3)); /* 12 */
printf("%d\n", pf[1](9, 3)); /* 6  */
printf("%d\n", pf[2](9, 3)); /* 27 */
printf("%d\n", pf[3](9, 3)); /* 3  */

getchar();
return 0;
}

``````

3. 用函数指针做参数:
``````#include <stdio.h>

int add(int x, int y) {return(x + y);}
int sub(int x, int y) {return(x - y);}
int mul(int x, int y) {return(x * y);}
int div(int x, int y) {return(x / y);}

int math(int(*pfun)(int, int), int x, int y) {
return pfun(x, y);
}

int main(void)
{
printf("%d\n", math(add, 9, 3)); /* 12 */
printf("%d\n", math(sub, 9, 3)); /* 6  */
printf("%d\n", math(mul, 9, 3)); /* 27 */
printf("%d\n", math(div, 9, 3)); /* 3  */

getchar();
return 0;
}

``````

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