"C-C ++"；关于后缀/前缀操作顺序的玩笑 [英] "C - C++" joke about postfix/prefix operation ordering

问题描述

我的朋友给我开了个玩笑:

My friend sent me a joke:

问C和C ++有什么区别?

Q. What's the difference between C and C++?

A.没什么，因为:(C-C ++ == 0)

A. Nothing, because: (C - C++ == 0)

我试图更改订单并被卡住.

I tried to change order and got stuck.

看下面的代码:

public class Test {
    public static void main(String args[]) {
        int c = 10;         
        System.out.println(c++ - c);
        System.out.println(++c - c);        
    }
}

为什么返回:

-1
0

我了解后缀和前缀增量.为什么这不是结果?

I understand postfix and prefix increment. Why isn't this the result?

0
1

推荐答案

因为在第一个示例中，c始于10.c++递增c并返回10，因此第二个c现在求值为11，因为它已递增.因此计算出的最终表达式是10 - 11，等于-1.

Because in the first example, c starts out 10. c++ increments c and returns 10, so the second c now evaluates to 11 since it was incremented. So the ultimate expression evaluated is 10 - 11, which equals -1.

在第二个示例中，++c再次递增c，但由于它是预递增的，所以返回12.第二个c的计算结果也为12，因为它是存储在c中的新值.因此该表达式最终被评估为12 - 12，等于0.

In the second example, ++c increments c again but returns 12 since it is a pre-increment. The second c evaluates to 12 as well, since it's the new value stored in c. So that expression ultimately is evaluated as 12 - 12, which equals 0.

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