How to check for equals? (0 == i) or (i == 0) [closed]

Answer 1

if(DialogResult.OK == MessageBox.Show("Message")) ...

I would always recommend writing the comparison this way. If the result of MessageBox.Show("Message") can possibly be null, then you risk a NPE/NRE if the comparison is the other way around.

Mathematical and logical operations aren't reflexive in a world that includes NULLs.

Answer 2

Third option - disallow assignment inside conditionals entirely:

In high reliability situations, you are not allowed (without good explanation in the comments preceeding) to assign a variable in a conditional statement - it eliminates this question entirely because you either turn it off at the compiler or with LINT and only under very controlled situations are you allowed to use it.

Keep in mind that generally the same code is generated whether the assignment occurs inside the conditional or outside - it's simply a shortcut to reduce the number of lines of code. There are always exceptions to the rule, but it never has to be in the conditional - you can always write your way out of that if you need to.

So another option is merely to disallow such statements, and where needed use the comments to turn off the LINT checking for this common error.

-Adam

Answer 3

Well, it depends on the language and the compiler in question. Context is everything.

In Java and C#, the "assignment instead of comparison" typo ends up with invalid code apart from the very rare situation where you're comparing two Boolean values.

I can understand why one might want to use the "safe" form in C/C++ - but frankly, most C/C++ compilers will warn you if you make the typo anyway. If you're using a compiler which doesn't, you should ask yourself why :)

The second form (variable then constant) is more readable in my view - so anywhere that it's definitely not going to cause a problem, I use it.

Answer 4

In C, yes, but you should already have turned on all warnings and be compiling warning-free, and many C compilers will help you avoid the problem.

I rarely see much benefit from a readability POV.

Answer 5

I think it's just a matter of style. And it does help with accidentally using assignment operator.

I absolutely wouldn't ask the programmer to grow up though.

Answer 6

I prefer the second one, (i == 0), because it feel much more natural when reading it. You ask people, "Are you 21 or older?", not, "Is 21 less than or equal to your age?"