Should I test == 1 or != 0?

Question

Hey.

I was coding here the other day, writing a couple of if statements with integers that are always either zero or one. I asked myself:

Should test against 1 or 0?

For example, given an int n, if I want to test if it's "true", should I use n == 1 or n != 0?

Is there any difference at all?

Please don't answer with stuff regarding the int may being more/less than 1/0, that's not what I want to know.

Answer 1

Human's brain better process statements that don't contain negations, which makes "int == 1" better way.

Answer 2

It really depends. If you're using a language that supports booleans, you should use the boolean, not an integer, ie:

if (value == false)

or

if (value == true)

That being said, with real boolean types, it's perfectly valid (and typically nicer) to just write:

if (!value)

or

if (value)

There is really very little reason in most modern languages to ever use an integer for a boolean operation.

That being said, if you're using a language which does not support booleans directly, the best option here really depends on how you're defining true and false. Often, false is 0, and true is anything other than 0. In that situation, using if (i == 0) (for false check) and if (i != 0) for true checking.

If you're guaranteed that 0 and 1 are the only two values, I'd probably use if (i == 1) since a negation is more complex, and more likely to lead to maintenance bugs.

Answer 3

If only two values are possible, then I would use the first:

if(int == 1)

because it is more explicit. If there were no constraint on the values, I would think otherwise.

Answer 4

(Assuming your ints can only be 1 or 0) The two statements are logically equivalent. I'd recommend using the == syntax though because I think it's clearer to most people when you don't introduce unnecessary negations.

Answer 5

When using integers as booleans, I prefer to interpret them as follows: false = 0, true = non-zero.

I would write the condition statements as int == 0 and int != 0.

Answer 6

A Daft question really. If you're testing for 1, test for 1, if you're testing for zero, test for zero.

The addition of an else statement can make the choice can seem arbitrary. I'd choose which makes the most sense, or has more contextual significance, default or 'natural' behaviour suggested by expected frequency of occurrence for example.

This choice between int == 0 and int != 1 may very well boil down to subjective evaluations which probably aren't worth worrying about.

Answer 7

If you're working with values that can only be 1 or 0, then I suggest you use boolean values to begin with and then just do if (bool) or if (!bool).

Answer 8

In language where int that are not 0 represents the boolean value 'true', and 0 'false', like C, I will tend to use if (int != 0) because it represents the same meaning as if (int) whereas int == 1 represents more the integer value being equal to 1 rather than the boolean true. It may be just me though. In languages that support the boolean type, always use it rather than ints.

Answer 9

To be honest if the value of int is just 1 or 0 you could even say:

if (int)

and that would be the same as saying

if (int != 0)

but you probably would want to use

if (int == 1)

because not zero would potentially let the answer be something other than 1 even though you said not to worry about it.

Answer 10

I would say it depends on the semantics, if you condition means

while ( ! abort ) negation is ok.

if ( quit ) break; would be also ok.

Answer 11

IF INT IS 1
NEXT SENTENCE
ELSE MOVE "INT IS NOT ONE" TO MESSAGE.

Answer 12

Two points:

1) As noted above, being more explicit is a win. If you add something to an empty list you not only want its size to be not zero, but you also want it to be explicitly 1.

2) You may want to do (1 == int) That way if you forget an = you'll end up with a compile error rather than a debugging session.

Answer 13

if( is_numeric( $int ) ) { its a number }
elseif( !$int ) { $int is not set or false }
else { its set but its not a number }

end of discussion :P

Answer 14

I agree with what most people have said in this post. It's much more efficient to use boolean values if you have one of two distinct possibilities. It also makes the code a lot easier to read and interpret.

if(bool) { ... }

Answer 15

I was from the c world. At first I don't understand much about objective-c. After some while, I prefer something like:

if (int == YES)

or

if (int == NO)

in c, i.e.:

if (int == true)
if (int == false)

these days, I use varchar instead of integer as table keys too, e.g.

 name   marital_status
------  --------------
 john      single
 joe       married

is a lot better than:

 name   marital_status
------  --------------
 john         S
 joe          M

or

 name   marital_status
------  --------------
 john         1
 joe          2

Answer 16

As others have said, using == is frequently easier to read than using !=.

That said, most processors have a specific compare-to-zero operation. It depends on the specific compiler, processor, et cetera, but there may be an almost immeasurably small speed benefit to using != 0 over == 1 as a result.

Most languages will let you use if (int) and if (!int), though, which is both more readable and get you that minuscule speed bonus.

Answer 17

I'm paranoid. If a value is either 0 or 1 then it might be 2. May be not today, may be not tomorrow, but some maintenance programmer is going to do something weird in a subclass. Sometimes I make mistakes myself [shh, don't tell my employer]. So, make the code say tell me that the value is either 0 or 1, otherwise it cries to mummy.

if (i == 0) {
    ... 0 stuff ...
} else if (i == 1) {
    ... 1 stuff ...
} else {
    throw new Error();
}

(You might prefer switch - I find its syntax in curly brace language too heavy.)