是这些(bCondition == NULL)和(NULL == bCondition)之间的区别? [英] What is the difference between these (bCondition == NULL) and (NULL==bCondition)?
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问题描述
在探索MSDN网站,大部分的病情检查地方,他们使用的是(NULL == bCondition)。
While exploring msdn sites ,most of the condition checking places they are using (NULL == bCondition).
什么是使用这些符号的目的是什么?
what is the purpose of using these notations?
提供一些示例来解释这些吧。
Provide some sample to explain these please.
感谢。
推荐答案
使用 NULL的==条件
在错字的情况下,提供了更多有用的行为,当赋值运算符 =
不小心使用,而随后比较运算符 ==
:
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编译器给出了前一种情况的警告,有没有这样的警告在许多语言。
C-compiler gives a warning in the former case, there are no such warnings in many languages.
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