Why is `NULL == bCondition` Preferred Over `bCondition == NULL` in Programming?

Understanding the Difference between (bCondition == NULL) and (NULL == bCondition)

In programming, it's crucial to understand the subtle nuances between different expressions. One such question frequently encountered involves the comparison of a variable to NULL. While both (bCondition == NULL) and (NULL == bCondition) may seem equivalent, there is a significant difference between them.

Purpose of the Notation

The common practice of using (NULL == bCondition) predominantly stems from defensive programming principles. It provides added safety in scenarios where an inadvertent assignment operator (=) is used in place of the comparison operator (==). Consider the following example:

if (bCondition = NULL)  // Typo here
{
 // Code never executes
}

In this erroneous usage, the assignment operator (=) erroneously assigns NULL to bCondition instead of comparing it. This results in a condition that always evaluates to false, effectively preventing the code within the if block from executing.

Compiler Behavior

In contrast, using (NULL == bCondition) introduces a slight advantage. It safeguards against this typo by causing the compiler to raise an error:

if (NULL = bCondition) // Error -> Compiler complains
{
 // ...
}

The compiler recognizes the misuse of the assignment operator and generates an error message. This serves as a valuable safety check, preventing the potential runtime error that could arise from the first example.

Additional Points

It's important to note that the behavior of the compiler may vary depending on the programming language being used. In certain languages, like C, the former example may trigger a warning rather than an error. However, in most modern languages, compilers are designed to provide more robust error handling, ensuring that such typos are detected and highlighted during compilation.

Therefore, while both (bCondition == NULL) and (NULL == bCondition) achieve the same logical comparison, it's generally recommended to adopt the latter notation as a best practice for safety and adherence to defensive programming guidelines.

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