为什么一些经验丰富的程序员用变量前的值写比较？ [英] Why do some experienced programmers write comparisons with the value before the variable?

问题描述

可能重复项：

如何检查是否等于？ （0 == i）或（i == 0）

为什么经常会看到 null！= variable而不是变量！=空在C＃中？

我一直在这里看一个奇怪的教程以及一些DirectX代码，并注意到许多经验丰富的C ++程序员以以下方式编写表达式：

 （< constant> ; ==< variable>）
  

而不是我传统的智慧似乎更喜欢：

 （< variable> ==< constant>）
  

例如 if（NULL == ptr），而不是 if（ptr == NULL）。我更喜欢第二种选择，如果没有其他理由选择前一种，我的理由是该变量似乎是表达式的接收端。

但是我怀疑前者是用来避免通过使用 = 来无意中将常量的值赋给变量的而不是 == 。

解决方案

是的，这是正确的。这是为了检测 = 的错字，而不是 == 的错字。

Possible Duplicates:
How to check for equals? (0 == i) or (i == 0)
Why does one often see “null != variable” instead of “variable != null” in C#?

I've been having a look at an odd tutorial here and there as well as some DirectX code and noticed that many experienced C++ programmers write expressions in the following way:

(<constant> == <variable>)

rather than what my conventional wisdom seems to prefer:

(<variable> == <constant>)

E.g. if (NULL == ptr) rather than if (ptr == NULL). I prefer the second alternative, if there are no other reasons for choosing the former, my reason being that the variable seems to be the "receiving" end of the expression.

But I suspect the former is used to avoid inadvertently assigning the value of the constant to the variable by using = rather than ==. Would that be correct?

解决方案

Yes, that's correct. It's to detect the typo of = instead of ==.

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