Are there any plans for adding a 'mutableIncrement...

# language-proposals

[littlelightcz]

Are there any plans for adding a 'mutableIncrement' operator? Because right now I am not able to write my own extension function for this use case that would behave like this:

val foo = AtomicInteger(0)
foo++

Current increment operator would allow me to work only with var foo, but this is obviously not what I want. In my use case I want to launch N coroutines and show a progress bar with how many of them have already finished (tracked in the foo AtomicInteger)

[Matej Drobnič]

Would overriding add(Integer) work?

[Matej Drobnič]

because ++ is basically shorthand for += 1

[Ruckus]

Note the docs say (about the inc and dec operators):

They shouldn't mutate the object on which the inc or dec was invoked.

https://kotlinlang.org/docs/reference/operator-overloading.html

[littlelightcz]

@Matej Drobnič hmmm nope, if you mean plusAssign operator then this works only for foo += 1

[littlelightcz]

@Ruckus exactly ... so maybe it would be nice to introduce the mutable versions of inc/dec to enable this use case, but it's just a syntactic sugar, not a big deal anyway😊

[elizarov]

http://kotl.in/issue (there does not seem to be one)

[littlelightcz]

Thanks Roman, will check it out and eventually propose there😊

[Ruckus]

@littlelightcz Would it be a different operator? If not, what happens if you override both in the same class?

[Ruckus]

Or in some sort of class hierarchy?

class Thing {
    operator fun inc() { ... }
}
class MutableThing : Thing() {
    operator fun mutableInc() { ... }
}

[littlelightcz]

@Ruckus yes, I would propose a brand new operator for this, could be named e.g. mutableInc() and vice versa for decrementing

[Ruckus]

By new operator, I meant a new symbol. If you used the same symbol (++) for both inc and mutableInc, you would have to resolve the conflict I showed above (what would MutableThing()++ do?). If you also intended a new symbol, did you have one in mind?

[elizarov]

Please, don’t try to think about this feature in vacuum. There is already a Kotlin design for a += b that works both for mutable classes via a.plusAssign(b) and for immutable classes via a = a.plus(b). If something in that direction is done for ++, then it has to have similar design or it is a no-go.

[Ruckus]

Ah, fair point. Thanks for the reminder @elizarov

[littlelightcz]

Proposal created: https://youtrack.jetbrains.com/issue/KT-31612 , thank you for your inputs.