Not keyword vs = False when checking for false boolean condition

Question

When I'm using an If statement and I want to check if a boolean is false should I use the "Not" keyword or just = false, like so

If (Not myboolean) then

vs

If (myboolean = False) then

Which is better practice and more readable?

Answer 1

Since there's no functional difference between either style, this is one of those things that just comes down to personal preference.

If you're working on a codebase where a standard has already been set, then stick to that.

Answer 2

Definitely, use "Not". And for the alternately, use "If (myboolean)" instead of "If (myboolean = true)"

The works best if you give the boolean a readable name:

 if (node.HasChildren)

Answer 3

! condition

In C and pre-STL C++, "!condition" means condition evaluates to a false truth value, whereas "condition == FALSE" meant that the value of condition had to equal what the system designed as FALSE. Since different implementations defined it in different ways, it was deemed better practice to use !condition.

UPDATE: As pointed out in the comment -- FALSE is always 0, it's TRUE that can be dangerous.

Answer 4

Definitely use "Not", consider reading it aloud.

If you read aloud:

If X is false Then Do Y Do Y

Versus

If Not X Then Do Y

I think you'll find the "Not" route is more natural. Especially if you pick good variable names or functions.

Code Complete has some good rules on variable names. http://cc2e.com/Page.aspx?hid=225 (login is probably required)

Answer 5

Use True and False to set variables, not to test them. This improves readability as described in the other answers, but it also improves portability, particularly when best practices aren't followed.

Some languages allow you to interchange bool and integer types. Consider the contrived example:

int differentInts(int i, int j)
{
   return i-j;  // Returns non-zero (true) if ints are different.
}

. . .
if (differentInts(4, 8) == TRUE)
   printf("Four and Eight are different!\n");
else
   printf("Four and Eight are equal!\n");

Horrible style, but I've seen worse sneak into production. On other people's watches, of course. :-)

Answer 6

Additionally to the consensus, when there is both a true case and a false case please use

if (condition)
    // true case
else
    // false case

rather than

if (not condition)
    // false case
else
    // true case

(But then I am never sure if python's x is not None is the true-case or the false case.)

Answer 7

Something else: Omit the parentheses, they’re redundant in VB and as such, constitute syntactic garbage.

Also, I'm slightly bothered by how many people argue by giving technical examples in other languages that simply do not apply in VB. In VB, the only reasons to use If Not x instead of If x = False is readability and logic. Not that you’d need other reasons.

Completely different reasons apply in C(++), true. Even more true due to the existence of frameworks that really handle this differently. But misleading in the context of VB!