Why Use `NULL == bCondition` Instead of `bCondition == NULL`?

Understanding Comparison Operators: (bCondition == NULL) vs. (NULL == bCondition)

While exploring documentation, it's common to come across condition checks using the syntax (NULL == bCondition). This raises questions about the purpose of such notations.

In this context, both (bCondition == NULL) and (NULL == bCondition) evaluate to true when bCondition is NULL. However, there's a subtle difference that becomes apparent in the case of a typo.

Typo Avoidance:

The use of NULL == condition provides an additional layer of safety in case of a typo. If an assignment operator "=" is mistakenly used instead of the comparison operator "==", it leads to a compiler error with (NULL = bCondition). In contrast, (bCondition = NULL) may not raise a warning in some languages, allowing such typos to go undetected.

For instance, consider the following code:

if (bCondition = NULL)  // typo here
{
 // code never executes
}

In this scenario, the typo results in an assignment of NULL to bCondition. Consequently, bCondition becomes NULL, and the condition evaluates to true. However, the programmer intended to check if bCondition was already NULL.

Using (NULL == bCondition) would have triggered a compiler error, highlighting the typo and preventing the incorrect behavior.

Examples:

Here are some examples to illustrate the usage of these notations:

// Check if bCondition is NULL
if (NULL == bCondition) { cout << "bCondition is NULL" << endl; }

// Check if pointer ptr is NULL
if (ptr == NULL) { delete ptr; }

// Check if an array is NULL
int* arr = NULL;
if (arr == NULL) { cout << "Array is NULL" << endl; }

In conclusion, using (NULL == condition) instead of (condition == NULL) enhances error detection by providing more explicit and robust code. It prevents typos from going unnoticed and ensures that intention matches implementation.

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