Why do some experienced programmers write comparisons with the value before the variable? [duplicate]

Answer 1

That used to be the case, yes. Of course, nowadays almost all compilers warn about assignments in if() conditions, so the advantage is only there for people who routinely suppress warnings.

Answer 2

Yes, that's correct. It's to detect the typo of = instead of ==.

Answer 3

This has been dubbed as a "Yoda Conditional"!

See here https://stackoverflow.com/questions/2349378/new-programming-jargon-you-coined

I really like that term because:

if(Light::On == light)

Reads as:

"If on is the light"

As stated already, this is used to prevent incorrect assignment. It could be argued that this practice is archaic based on modern IDEs but I still think it is good practice.

Answer 4

To catch the difference between assigning and comparing.

If you mean:

if (ptr == foo)

but type

if (ptr = foo)

if will still be valid code, since ptr = foo will evaluate to a boolean check on ptr after it has been set to the value of foo. Obviously, you don't want this.

However, I find it hurts readability considerably, and given that most IDE's and preprocessors will catch this anyway, never use this style.

Answer 5

It avoids that you write var = NULL. Writing NULL = var will yield an error. So you're right :-)

Answer 6

As a java developer I tend to write expressions like this:

   //primitive check
   if(constant == variable)

   //Object check
   if(constant.equals(variable))

This is particularly important for the object because the expression doesn't error if the variable is null. If the expression were in the other order, a null variable would error. I maintain consistency and do the same order for primitives.