C-指针函数与函数指针

指针函数

• 返回指针类型的结果的函数

#include <stdio.h>

int* fun(int* a)
{
    return a;
}

int main()
{
    int a = 10;
    int* p = &a;
    a = 20;
    printf("%d", *fun(p));  // 20
    return 0;
}

函数指针

• 指向一个函数的指针

#include <stdio.h>

int sum(int x, int y)
{
    return x + y;
}

int main()
{
    int (*p)(int, int) = sum;
    
    int result1 = (*p)(1, 2);
    int result2 = p(1, 2);  // p(1, 2) == sum(1, 2)
    return 0;
}

• 回调函数 - 通过函数指针调用的函数

#include <stdio.h>

int sum(int x, int y)
{
    return x + y;
}

int minus(int x, int y)
{
    return x - y;
}

int operate(int (*p)(int, int), int x, int y)
{
    return p(x, y);  // 回调函数
}

int main()
{
    int a = 1, b = 2;
    int (*p)(int, int);
    puts("请输入一个'+'或'-':");
    while(1)
    {
        int operator = getchar();
        if(operator == '+')
        {
            p = sum;
            break;
        }
        else if(operator == '-')
        {
            p = minus;
            break;
        }
        else puts("---Error---");
    }
    int result = operate(p, a, b);
    printf("%d", result);
    return 0;
}