問(wèn)題描述
在瀏覽 msdn 站點(diǎn)時(shí)，他們使用的大多數(shù)條件檢查位置 (NULL == bCondition).
While exploring msdn sites ,most of the condition checking places they are using (NULL == bCondition).
使用這些符號(hào)的目的是什么?
what is the purpose of using these notations?
請(qǐng)?zhí)峁┮恍┦纠齺?lái)解釋這些.
Provide some sample to explain these please.
謝謝.
推薦答案
當(dāng)賦值運(yùn)算符 = 被意外使用而不是比較運(yùn)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 在前一種情況下會(huì)給出警告，很多語(yǔ)言都沒(méi)有這樣的警告.
C-compiler gives a warning in the former case, there are no such warnings in many languages.
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