C语言 | 回调函数实践实例

C语言 | 回调函数实践实例

实例1：

/*******************************************************************
 *   > File Name: callback.c
 *   > Create Time: Wed Sep  8 15:37:41 2021
 ******************************************************************/
#include <stdio.h>
#include <string.h>

double add(int a, int b)
{
    printf("%s\n", __func__);
    return (double)(a+b);
}

double sub(int a, int b)
{
    printf("%s\n", __func__);
    return (double)(a - b);
}

double mul(int a, int b)
{
    printf("%s\n", __func__);
    return (double)(a*b);
}

double div(int a, int b)
{
    printf("%s\n", __func__);
    return ((double)a/(double)b);
}

typedef struct _Calculator
{
    char objname[24];
    double (*pAdd)(int, int);
    double (*pSub)(int, int);
    double (*pMul)(int, int);
    double (*pDiv)(int, int);
}CALCULATOR, *pCALCULATOR;


int main(int argc, char* argv[])
{
    printf("a + b = %f\n", add(100, 200));
    printf("a - b = %f\n", sub(100, 200));
    printf("a * b = %f\n", mul(100, 200));
    printf("a / b = %f\n", div(100, 200));

    double (*pFunc)(int, int);
    pFunc = add;
    pFunc(10,10);

    CALCULATOR obj;
    strcpy(obj.objname, "calculator");
    obj.pAdd = add;
    obj.pSub = sub;
    obj.pMul = mul;
    obj.pDiv = div;

    printf("============================>\n");
    obj.pAdd(10,10);
    obj.pSub(10,10);
    obj.pMul(10,10);
    obj.pDiv(10,10);

    return 0;
}

编译、运行：

lanfeiy@yelanfei ~/workspace/test
$ make -f c.mk callback
gcc -o callback callback.c -g -Wall

lanfeiy@yelanfei ~/workspace/test
$ ./callback.exe
add
a + b = 300.000000
sub
a - b = -100.000000
mul
a * b = 20000.000000
div
a / b = 0.500000
add
============================>
add
sub
mul
div

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