波浪号运算符分别返回 -1、-2 而不是 0、1
我对此感到有些困惑.我认为 C++ 中的 ~ 运算符应该以不同的方式工作(不是 Matlab-y).这是一个最小的工作示例:
I'm kind of puzzled by this. I thought the ~ operator in C++ was supposed to work differently (not so Matlab-y). Here's a minimum working example:
#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;
}
这是我的输出:
1-2
0-1
我希望有人对此有所了解.
I hope someone will have some insight into this.
推荐答案
这正是应该发生的事情:当你反转零的二进制表示时,你得到负一;当你反转一的二进制表示时,你会在二进制补码表示中得到负二.
This is exactly what should happen: when you invert the binary representation of zero, you get negative one; when you invert binary representation of one, you get negative two in two's complement representation.
00000000 --> ~ --> 11111111 // This is -1
00000001 --> ~ --> 11111110 // This is -2
请注意,即使您以 bool
开头,运算符 ~
也会根据整数规则将值提升为 int
促销.如果您需要将 bool
反转为 bool
,请使用运算符 !
而不是 ~
.
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. If you need to invert a bool
to a bool
, use operator !
instead of ~
.
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