What is the difference between these (bCondition == NULL) and (NULL==bCondition)?

Question

While exploring msdn sites ,most of the condition checking places they are using (NULL == bCondition).

what is the purpose of using these notations?

Provide some sample to explain these please.

Thanks.

Answer 1

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 gives a warning in the former case, there are no such warnings in many languages.

Answer 2

It's called Yoda Conditions. (The original link, you need high rep to see it).

It's meant to guard against accidental assignment = in conditions where an equality comparison == was intended. If you stick to Yoda by habit and make a typo by writing = instead of ==, the code will fail to compile because you cannot assign to an rvalue.

Does it worth the awkwardness? Some disagree, saying that compilers do issue a warning when they see = in conditional expressions. I say that it simply happened just two or three times in my lifetime to do this mistake, which does not justify changing all the MLOCs I wrote in my life to this convention.