这些 (bCondition == NULL) 和 (NULL==bCondition) 之间有什么区别?
在浏览 msdn 站点时，他们使用的大多数条件检查位置 (NULL == bCondition).
While exploring msdn sites ,most of the condition checking places they are using (NULL == bCondition).
使用这些符号的目的是什么?
what is the purpose of using these notations?
请提供一些示例来解释这些.
Provide some sample to explain these please.
谢谢.
推荐答案
当赋值运算符 = 被意外使用而不是比较运算符 ==:
The use of NULL == condition provides more useful behaviour in the case of a typo, when an assignment operator = is accidentally used rather then the comparison operator ==:
if (bCondition = NULL) // typo here
{
// code never executes
}
if (NULL = bCondition) // error -> compiler complains
{
// ...
}
C-compiler 在前一种情况下会给出警告，很多语言都没有这样的警告.
C-compiler gives a warning in the former case, there are no such warnings in many languages.
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