为什么9和49输出？ 9是正确的，但为什么k = 49？ [英] Why 9 and 49 output ? 9 is correct but why k=49 ?

问题描述

#include <stdio.h>
#define PRODUCT(x) ((x)*(x))
int main()
{
    int i=3,j,k;
    j=PRODUCT(i++);
    k=PRODUCT(++i);
    printf("%d %d",j,k);
    return 0;
}

推荐答案

我们可以逐步完成此代码：



int i = 3，j，k;



声明变量，i的值为3.



j = PRODUCT（i ++）;



调用宏PRODUCT，i的值为3， 3 * 3 = 9.

现在此后因为（x）*（x），i的值将增加两次 ！

i的值现在是5.



k = PRODUCT（++ i）;



调用宏PRODUCT但之前因为（x）*（x）而i的值将增加两次是7和7 * 7 = 49。

We can go through this code step-by-step:

int i=3,j,k;

The variables are declared, the "i" has value of 3.

j=PRODUCT(i++);

The macro PRODUCT is called, the value of "i" is first 3 and 3*3 = 9.
Now after this the value of "i" will be incremented twice because of (x)*(x)!
The value of "i" is now 5.

k=PRODUCT(++i);

The macro PRODUCT is called but before the value of "i" will be incremented twice because of (x)*(x) and is 7 and 7*7 = 49.

这篇关于为什么9和49输出？ 9是正确的，但为什么k = 49？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！