回调函数实例——数学计算

#include<stdio.h>
#include<malloc.h>

/****************************************
 * 函数指针结构体
 ***************************************/
typedef struct _OP
{
    float (*p_add)(float, float);
    float (*p_sub)(float, float);
    float (*p_mul)(float, float);
    float (*p_div)(float, float);
} OP;

/****************************************
 * 加减乘除函数
 ***************************************/
float ADD(float a, float b)
{
    return a + b;
}

float SUB(float a, float b)
{
    return a - b;
}

float MUL(float a, float b)
{
    return a * b;
}

float DIV(float a, float b)
{
    return a / b;
}

/****************************************
 * 初始化函数指针
 ***************************************/
void init_op(OP *op)
{
    op->p_add = ADD;
    op->p_sub = SUB;
    op->p_mul = &MUL;
    op->p_div = &DIV;
}

/****************************************
 * 库函数
 ***************************************/
float add_sub_mul_div(float a, float b, float (*op_func)(float, float))
{
    return (*op_func)(a, b);
}

int main(int argc, char *argv[])
{
    OP *op = (OP *)malloc(sizeof(OP));
    init_op(op);

    /* 直接使用函数指针调用函数 */
    printf("ADD = %f, SUB = %f, MUL = %f, DIV = %f\n", 
            (op->p_add)(1.3, 2.2), 
            (*op->p_sub)(1.3, 2.2),
            (op->p_mul)(1.3, 2.2),
            (*op->p_div)(1.3, 2.2));

    /* 调用回调函数 */
    printf("ADD = %f, SUB = %f, MUL = %f, DIV = %f\n",
           add_sub_mul_div(1.3, 2.2, ADD),
           add_sub_mul_div(1.3, 2.2, SUB),
           add_sub_mul_div(1.3, 2.2, MUL),
           add_sub_mul_div(1.3, 2.2, DIV));

    return 0;
}