==运算符和操作数 [英] == Operator and operands

问题描述

我要检查一个值是否等于1.下面的代码行是否有任何区别

I want to check whether a value is equal to 1. Is there any difference in the following lines of code

评估值== 1

1 ==评估值

关于编译器执行

推荐答案

在大多数语言中，都是同一回事.

In most languages it's the same thing.

人们经常做1 ==计算值，因为1不是左值.这意味着您不能偶然进行作业.

People often do 1 == evaluated value because 1 is not an lvalue. Meaning that you can't accidentally do an assignment.

示例:

if(x = 6)//bug, but no compiling error
{
}

相反，您可以强制执行编译错误而不是错误:

Instead you could force a compiling error instead of a bug:

if(6 = x)//compiling error
{
}

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现在，如果x不是int类型，并且您使用的是C ++之类的东西，那么用户可能已经创建了operator ==(int)覆盖，这使这个问题有了新的含义.在这种情况下，6 == x不会编译，但是x == 6会编译.

---

Now if x is not of int type, and you're using something like C++, then the user could have created an operator==(int) override which takes this question to a new meaning. The 6 == x wouldn't compile in that case but the x == 6 would.

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