Callback function

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;
}

void menu()
{
	printf("******************************\n");
	printf("****** 1.add      2.sub ******\n");
	printf("****** 3.mul      4.div ******\n");
	printf("******      0.exit     *******\n");
	printf("******************************\n");
}

int Calc(int (*pf)(int,int))//函数指针
{
	int x = 0;
	int y = 0;
	printf("请输入2个操作数：>");
	scanf("%d %d", &x, &y);
	return pf(x, y);
}

int main()
{
	//计算器-计算整型变量的加、减、乘、除
	int input = 0;
	do
	{
		menu();
		int ret = 0;
		printf("请选择：>");
		scanf("%d", &input);
		switch (input)
		{
		case 1:
			ret = Calc(Add);//回调函数机制
			printf("ret = %d\n", ret);
			break;
		case 2:
			ret = Calc(Sub);//回调函数机制
			printf("ret = %d\n", ret);
			break;
		case 3:
			ret = Calc(Mul);//回调函数机制
			printf("ret = %d\n", ret);
			break;
		case 4:
			ret = Calc(Div);//回调函数机制
			printf("ret = %d\n", ret);
			break;
		case 0:
			printf("退出程序\n");
			break;
		default:
			printf("选择错误，重新选择\n");
			break;
		}
	} while (input);
	return 0;
}