c - 什么是函数指针？

Question

用简单的语言来说，什么是函数指针？

Answer 1

用简单的英语来说，

A FUNCTION_POINTER is a pointer which points towards the address of fuction's first instruction, like a POINTER which points towards the address of a variable.

举一个程序示例来理解这个概念

Sum of all integers upto the user i/p

-

#include <stdio.h>

int IsAny(long n)
{
    return 1;
}

long AddIf(long limit, int (*funPointer)(long))
{
    long sum = 0;
    register int i;

    for(i = 1; i <= limit; ++i)
    {
        if(funPointer(i))
            sum += i;
    }

    return sum;
}

int main(void)
{
    long l, total;

    printf("Enter a positive integer: ");
    scanf("%ld", &l);

    total = AddIf(l, IsAny);
    printf("Sum of all integers upto %ld is %ld\n", l, total);
}

此处调用 FUNCTION_POINTER 以通过声明调用 AddIf 中的 IsAny 函数 作为 AddIf 函数中的 int (*funPointer)(long))