C ++，增量运算符 [英] C++, increment operator

问题描述

int k, n = 2;
k = (k = n + 5)++;
cout << k << '\n';
k = ++(k = n + 5);
cout << k << '\n';

我以为第一个是7，第二个是8.但是令人惊讶的是，输出都是8.
有人可以告诉我吗?

I thought the 1st one is 7 and the 2nd is 8. But the output is surprisingly both 8.
Anyone can tell me about this? Thx in advance.

推荐答案

在C ++中，它未定义为i = i++，因为i在同一表达式中被修改了两次，并且顺序未定义为operator=不是序列点.

请参见 http://en.wikipedia.org/wiki/Sequence_point [

In C++, it is undefined as is i = i++ since i is modified twice in the same expression and the order is not defined as operator= is not a sequence point.

See http://en.wikipedia.org/wiki/Sequence_point[^]

第一个语句也返回8，因为
当该语句的执行完成

The 1st statement also returning 8 because
when the execution of this statement is completed

k = (k = n + 5)++;

时，也会进行后递增，并且得到的结果为8.

如果打印(k = n + 5)++，则输出为7.

then the postincrement also takes place and you are getting result as 8.

if you print (k = n + 5)++ then the output will be 7.

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