Is there any rule as to when I should use `.not()` and when I should use good old `!` <https://kotli...

# getting-started

[Jacob]

Is there any rule as to when I should use .not() and when I should use good old ! https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/not.html

[nanodeath]

I'd never use not()

[Jacob]

Someone on my team is using it. A lot. What should I tell him to discourage him?

[tseisel]

!condition is used in most programming languages (or at least in most of those I know). Because it is more familiar to non-Kotlin developers, I think i'ts more readable than condition.not(), especially in long conditions.
AFAIK the Kotlin compiler may not fully optimize the .not() function call in some cases, compared to when using !

[nanodeath]

I'd expect ! and .not() to be bytecode-equivalent since .not() is just an operator function, btw.

[nanodeath]

having a postfix negation method just seems unnatural to me. it's more obvious to say "not some condition" instead of "some condition, not"

[Even André Fiskvik]

I wonder if they were influenced by Borat english in this case 🤔 This is great... NOT!

[nanodeath]

I don't know for sure that you can "convince" someone of this based on merit alone...I'd say have a team style guide and enforce it.

[Jacob]

OK, but if its not a good idea, then what sort of cases was the operator designed for?

[Son]

Out of curiosity:

fun test(): Boolean = true
fun main () { test().not() }

// decompiled
public static final boolean test() { return true;}
public static final void main() { if (!test()) {} }

[Son]

I guess Kotlin doesn’t optimize that out

[Son]

@Jacob maybe for Unit testing during expects. I come from Jasmine/Mocha world and I see that a lot

[nanodeath]

I think it's just how the ! operator is implemented

[nanodeath]

just because you can call plus doesn't mean you're supposed to call it by that name

[nanodeath]

that's the kind of operation the JVM would optimize out I think

[ephemient]

@Son it'll optimize it with a const val, otherwise it's not constant and can't be inlined at compile time.

[elizarov]

@Jacob

Someone on my team is using it. A lot. What should I tell him to discourage him?

"You must unlearn what you have learned." (c) Yoda

[Joris PZ]

do not do do.not() do !do

[todd.ginsberg]

"House Style: `!not()`"