[英]tilde operator returning -1, -2 instead of 0, 1 respectively
I'm kind of puzzled by this. 我对此感到困惑。 I thought the ~ operator in C++ was supposed to work differently (not so Matlab-y). 我认为C ++中的〜运算符应该以不同的方式工作(不是Matlab-y)。 Here's a minimum working example: 这是一个最小的工作示例:
#include <iostream>
using namespace std;
int main(int argc, char **argv)
{
bool banana = true;
bool peach = false;
cout << banana << ~banana << endl;
cout << peach << ~peach << endl;
}
And here's my output: 这是我的输出:
1-2
0-1
I hope someone will have some insight into this. 我希望有人能对此有所了解。
This is exactly what should happen: when you invert the binary representation of zero, you get negative one; 这正是应该发生的事情:当你将二进制表示反转为零时,你会得到负数; when you invert binary representation of one, you get negative two in two's complement representation. 当你反转一个二进制表示时,你得到二进制补码表示的负二。
00000000 --> ~ --> 11111111 // This is -1
00000001 --> ~ --> 11111110 // This is -2
Note that even though you start with a bool
, operator ~
causes the value to be promoted to an int
by the rules of integer promotions. 请注意,即使您以bool
开头,operator ~
也会通过整数提升规则将值提升为int
。 If you need to invert a bool
to a bool
, use operator !
如果你需要将bool
反转为bool
,请使用operator !
instead of ~
. 而不是~
。
~ is bitwise NOT operator which means it flips all the bits. 〜是按位NOT运算符,这意味着它会翻转所有位。 For boolean NOT, you should be using ! 对于布尔值NOT,你应该使用! operator 操作者
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