Which is clearer form: if(!value) or if(flag == value)?

Question

I understand this is a subjective question, so I apologize if it needs to be closed, but I feel like it comes up often enough for me to wonder if there is a general preferen

Answer 1

I personally like

if ((value == false) == true) ...

cause this is verifying that the statement value is false is actually evaluating to a boolean true...

and, then, obviously, covering both posssibilites adds even more clarity,

if ((value == false) == true && (value == false) != false)

<grin/>

and for those of you who are real gluttons for clarity, and demand incontrovertible readability, I'd suggest

if (((value == false) == true && (value == false) != false) == true)

Answer 2

I don't think it's all that subjective. I have never seen it recommended in the longer form. Actually all the books and coding guides and "How to be a good programmer" HowTos I've read discourage it.

It falls in the same category as

if (value) {
  return true;
} else {
  return false;
}

OTOH, all the answers given here make my first statement kinda equal not true.

Answer 3

Whatever condition an if block should evaluate in order to execute must evaluate to true.

Hence, when value is false, the reason why if (!value) allows an if block to execute is because the ! operator essentially flips the false value of value to true, thus making the resultant condition within the parentheses evaluate into a true one that an if block needs in order to execute.

if (value), if (!value), if (flag == value), if (value == true), if (value == false), depending on what's to be achieved, are valid code. E.g. if (value == true) is very useful when value is a nullable boolean, because if (value) will give a syntax error, and if (value.Value == true) will throw exception if you didn't ensure that value is not null before the if block is executed.

Answer 4

I would never use if(value == true), so just for consistency I would also not use if(value != false).

Answer 5

I prefer the second option, the if (value == false) one. I gladly use if (~value) or if (not value) in languages that support it, but that ! just merges waaaaay too easily either with the variable name or opening braces or | or || operators... at least in my opinion.

Also, two things:

1. I never do if (value == true), and I'm aware I'm inconsistent. And although consistency is very important in my opinion, that pesky ! is simply worse.
2. I think it's really a matter of personal taste, just like the brace-on-a-newline debate. I would never criticize a teammate for silly little things like that, and I have a hard time understanding the people who will.

Answer 6

if(!value) is clearer and more "elegant", specially if you name boolean variables correctly

• isWhatever
• hasWhatever
• etc

Something like

if (Page.IsPostback == true)

seems redundant to me