C语言 逻辑否定在 C 中如何工作？
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How does logical negation work in C?
提问by Ben Fossen
I have been using ! (logical negation) in C and in other languages, I am curious does anyone know how to make your own ! function? or have a creative way of making one?
我一直在用！（逻辑否定）在 C 和其他语言中，我很好奇有没有人知道如何制作自己的！功能？或者有一种创造性的制作方式？
回答by Hans W
int my_negate(int x)
{
return x == 0 ? 1 : 0;
}
回答by Pascal Cuoq
!ecan be replaced by ((e)?0:1)
!e可以替换为 ((e)?0:1)
回答by t0mm13b
Remember the bang operator '!' or exclamation mark in english parlance, is built into the programming language as a means to negate.
记住 bang 运算符 '!' 或英语中的感叹号，是内置于编程语言中的一种否定方式。
Consider this ternary operator example:
考虑这个三元运算符示例：
(some condition) ? true : false;
Now, if that was negated, the ternary operator would be this
现在，如果这被否定，三元运算符将是这个
(some condition) ? false : true;
The common area where that can get some programmers in a bit of a fit is the strcmpfunction, which returns 0 for the strings being the same, and 1 for two strings not the same:
可以让一些程序员有点适应的公共区域是strcmp函数，对于相同的字符串返回 0，对于两个不同的字符串返回 1：
if (strcmp(foo, "foo")){
}
When really it should be:
真正应该是：
if (!strcmp(foo, "foo")){
}
In general when you negate, it is the opposite as shown in the ternary operator example...
一般来说，当你否定时，它是相反的，如三元运算符示例所示......
Hope this helps.
希望这可以帮助。
回答by bta
C considers all non-zero values "true" and zero "false". Logical negation is done by checking against zero. If the input is exactly zero, output a non-zero value; otherwise, output zero. In code, you can write this as (input == 0) ? 1 : 0(or you can convert it into an ifstatement).
C 认为所有非零值“真”和零“假”。逻辑否定是通过检查零来完成的。如果输入正好为零，则输出一个非零值；否则，输出零。在代码中，您可以(input == 0) ? 1 : 0将其编写为（或者您可以将其转换为if语句）。
When you ask how to "make your own ! method", do you mean you want to write a function that negates a logic value or do you want to define what the exclamation-point operator does? If the former, then the statement I posted above should suffice. If the latter, then I'm afraid this is something that can't be done in C. C++ supports operator overloading, and if doing this is a strict necessity then I would suggest looking there.
当您问如何“创建自己的 ! 方法”时，您的意思是要编写一个否定逻辑值的函数，还是要定义感叹号运算符的作用？如果是前者，那么我上面发布的声明就足够了。如果是后者，那么恐怕这在 C 中是无法完成的。C++ 支持运算符重载，如果这样做是绝对必要的，那么我建议在那里查看。
回答by thebretness
If you want to overload an operator, the proper prototype is:
如果要重载运算符，正确的原型是：
bool operator!();
I'm not a big fan of overloading operators, but some people like their syntactic sugar. EDIT: This is C++ only! Put it in the definition of your class.
我不是重载运算符的忠实粉丝，但有些人喜欢他们的语法糖。编辑：这只是 C++！把它放在你的类的定义中。
