Invert bool if true

Question

What is the most condense way to invert a boolean if another boolean is true. In other words, what is the shortest way of writing condition ? !value : value, preferably evaluating value only once?

Edit: Just so you know, I am passing the result to a method

To me it seems that "value = condition?!value:value" is the most condensed form. — gtgaxiola, Jan 06 '14 at 20:12
possible duplicate of [Easiest way to flip a boolean value?](http://stackoverflow.com/questions/610916/easiest-way-to-flip-a-boolean-value) — Sajad Karuthedath, Jan 06 '14 at 20:19
@gtgaxiola If you're looking for the most condensed form, using a xor is much shorter than using the ternary operator. — zakinster, Jan 06 '14 at 20:20
@SajadLfc No, this isn't a duplicate of that. This question has a little more to it. — arshajii, Jan 06 '14 at 20:20
@SajadLfc I don't think you can; a moderator will simply decline the flag. — arshajii, Jan 06 '14 at 20:24

score 14 · Accepted Answer · answered Jan 06 '14 at 20:14

14

The shortest way is

value ^= condition;

answered Jan 06 '14 at 20:14

Dawood ibn Kareem

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not the best form for passing into a method, but any programmer worth their salt knows that is short-hand for `value = value ^ condition`. Thanks for the help. – BrainStorm.exe Jan 06 '14 at 20:24
1

another way is `value = value != condition` – tuket Sep 01 '21 at 09:51

arshajii · Answer 2 · 2014-01-06T20:16:46.910

All you want is

if (condition)
    value = !value;

No need to bring the conditional operator in; that would just be unnecessary clutter. The reason this would be preferable over

value = condition ? !value : value;

is because the above performs an assignment irrespective of condition's value; if condition is false, we just assign value to itself. This works as well, but isn't really what you want logically. You want to invert value (i.e. perform an assignment) if condition is true. I would argue that the the second variant is simply a misuse of the conditional operator. Beyond that, the first variant is certainly more readable and easier to follow.

score 3 · Answer 3 · answered Jan 06 '14 at 20:13

3

You could try:

value = condition ^ value

Not the most readible solution though.

answered Jan 06 '14 at 20:13

zakinster

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score 2 · Answer 4 · answered Jan 06 '14 at 20:09

2

Is this what are you looking for?

if(condition)
   value = !value

answered Jan 06 '14 at 20:09

Selman Genç

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score 2 · Answer 5 · answered Jan 06 '14 at 20:11

2

Why would you even bother about the short or long even. Prefer more readable code. You can write

if (SomeCondition) {
    value = !value;
}

Since there is no need for else condition, since the value is value in else.

answered Jan 06 '14 at 20:11

Suresh Atta

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Sajad Karuthedath · Answer 6 · 2014-01-06T20:27:11.437

0

as your question says 'invert bool if true'

you should use:

 if(statement)
    {

    value=!value;
    }

edited Jan 06 '14 at 20:27

answered Jan 06 '14 at 20:12

Sajad Karuthedath

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With `if(statement==true)` you can easy make mistake by writing it like `if(statement=true)`. To avoid this kind of mistakes it is better to use [yoda conditions](http://en.wikipedia.org/wiki/Yoda_conditions): `if (true==statement)` or just `if(statement)` since `statement==true` is the same as just `statement`. – Pshemo Jan 06 '14 at 20:26
@Pshemo; Like Yoda conditions, I do. – Craig Tullis Mar 14 '14 at 22:25

score 0 · Answer 7 · answered Jun 27 '20 at 14:55

A good way is to have a function or method like this

boolean invert(boolean condition, boolean value){ return condition != value; }

In fact:

condition value  inversion
t           t      f
t           f      t
f           t      t
f           f      f

in the first 2 cases condition is true and inversion is performed, otherwise in the last two cases.

Invert bool if true

7 Answers7