在C ++中！(value)的用法是什么 [英] what is the use of !(value) in c++

问题描述

我有一个非常简单的问题.
我有一个程序，其中有人用过！像这样

I have very simple problem.
I have a program in which some one used ! like this

int main()
{
    int a;
    a=5;
    if (!a==0)
        cout<<"yes";
    else
        cout<<"no";
    return 0;
}

can any one tell me what is used of ''!'' in this program?

推荐答案

!a==b与a!=b不同.如上所述，检查您的优先级，它等于(!a) == (b)，因此首先将a取反，然后将其与b进行比较.

!a==b is not the same as a!=b. Check you precedence, as said above, this is equal to (!a) == (b) so first a is negated then compared to b.

！不是操作符.
!a==0读为不等于0".这是一个不好的用法，但是有效，通常将其写为a!=0，读为"a不等于0"


在这种情况下，如果a为0，程序将打印否"，否则将打印是".

另外，您会误输入.

! is the not operator.
!a==0 is read as "not a is equal to 0". This is a bad usage of it, but is valid, typically this would be written as a!=0, read "a is not equal to 0"


in this case the program prints "no" if a is 0, otherwise prints "yes".

Also, you misspelt return.

不要写这样的代码.

这样做:

if(！(a == 0))
{
...
}

或

if((！a)== 0)
{
...
}

我认为这是一种更好的方法.

Don''t write codes like that.

Do like this:

if( !(a==0))
{
...
}

or

if((!a) == 0)
{
...
}

I think it''s a better way.

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