Apparently I need to ask something the third time today: Is there any useful application to kinda “redeclaring” a method in an interface extending another interface or is it just a “cosmetic” thing? E.g.

Hello everyone ! I'm really glad to have joined this server 😊 I have a question about Jetpack Compose (Desktop, but idk if the problem exist in JC Android). Where should I ask 🙂 ?

Stupid control flow question When(something){ in group1 -> tada1 in group2 -> tada2 } but what if I wanna check when(string) and if the subsequent offered strings contain the value inside of my when?

val incomingString = "A lot of things that are not interesting but this: ThePath"
when(incomingString){
        "The Path" -> something
        "No Path" -> something
            else -> somethingElse
}

Better example

I have some problems with Intellij — the previous instance of the program doesn't stop if I start a new one despite having parallel run disabled. Also, it started for some reason running with Gradle and stopping it with Intellij causes it to “fail”

Can someone explain why is 

Kotlinx.html

 considered type safe?

quick question which i feel like i should know the answer to: if i have an immutable map and call .toMutableMap on it and change the resulting map, does it change the first immutable one?

collection class question: If I have a list of varying lengths of positive and negative integers how can I sum the sections w/ the same sign? example

[-1,-1,-1,1,1,-1,-1]

should yield

[-3,2,-2]

I can't figure out how to do this w/o iterating over the list, and keeping a bunch of mutable state. Is there fancy sequence of collection functions I could use to do this?

Wouldn't it just be a matter of iterating across, saving which "mode" you are in, negative or positive, and summing that way?

Let's say I have a

List<User>

and want to get a

List<String>

of their

name

property, is there a helper method for this?

Seems like there's no lowering / optimization for destructing array declaration of same data type.

var (e, f, c, d) = arrayOf(1, 10, 12, 55)

Seems to decompile to:

Integer[] var6 = new Integer[]{5, 44, 34};
boolean var8 = false;
int var2 = ((Number)var6[0]).intValue();
var8 = false;
int var3 = ((Number)var6[1]).intValue();
var8 = false;
int var4 = ((Number)var6[2]).intValue();
var8 = false;
int d = ((Number)var6[3]).intValue();

Is there a workaround to declare multiple variables concisely but also with an efficient handling performance wise?

Hi folks, I'm reading about Dart's null safety and based on their video, it says that Kotlin does not have this "Sound null safety". For what I understand reading the docs (https://dart.dev/null-safety) "Sound null safety" but looks like exactly what kotlin does when you are writing a full kotlin code, like a project that only uses others Kotlin libraries. Can someone clarify why kotlin is not "Sound null safety"? (image taken from )

Which is considered as a better style? Enums, sealed classes with singletons, or class with companion objects with val?

Hi all, I'm wondering what is the right channel (that's got some life to it) for talking about "here's this thing I made, looking for comments"?

Anyone know why the way I initialize this map compiles fine but throws a JVM error? https://stackoverflow.com/q/65068266/499125

This doesn't seem to go away, any body know how to create experimental annotation

I do wish that the toString of maps, lists and data classes was compilable.

Is there any ETA for Kotlin 1.4.30?

If a dependency artifact missing for a platform what's correct way to build in such situation? As an example KotlinLogging currently only supports Linux, so is there a way to define actual function which returns empty implementation of some of the expect functions in that lib (till lib extends support to other platform)?

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Is there a way to suppress "unused" warnings for all the public functions/classes in Intellij? (Java seems to have option but Kotlin doesn't)

Hello! Is it possible to create a typealias for an annotation? I want to do something like this (the code doesn't compile):

import androidx.annotation.FloatRange

typealias ProgressFloatRange = FloatRange(from = 0.0, to = 1.0, fromInclusive = true, toInclusive = true)

For the love of god, I can't find any mention in the docs on how to enable IR mode for JVM target... Maybe anyone here will know?

Hi all! There is a bunch of useful extension methods in Kotlin 1.4 like

kotlin.collections.sumOf

. I find it very useful, but I have a use case when I want to overload this function. Suppose I have a simple class

IntHolder

and an extension function

Iterable<T>.sumOf((T) -> IntHolder)

. How can I use both mine

sumOf

and prewritten

sumOf

from

kotlin.collections

? I have some workarounds like renaming this method or using

import as

for a

kotlin.collections.sumOf

, but those are not solutions, but just workarounds. Maybe you know the reason it doesn't work or you know how to make it work? As for me, right now it looks like a bug. I've already asked about this on StackOverflow but got no responses Here. The real use case is actually not that simple, but I believe the code below totally describes the whole situation.

import kotlin.experimental.ExperimentalTypeInference

data class IntHolder(val x: Int) {
    operator fun plus(other: IntHolder) = IntHolder(x + other.x)
}

@OptIn(ExperimentalTypeInference::class)
@OverloadResolutionByLambdaReturnType
inline fun <T> Iterable<T>.sumOf(f: (T) -> IntHolder) = fold(IntHolder(0)) { acc, i -> acc + f(i) }

fun main() {
    val range = 1..5
    val a = range.sumOf { it * 2 }  //here is an error
    val b = range.sumOf { IntHolder(it * 2) }
}

When using maps in Kotlin I often find myself writing things out like

myMap[k] = myMap[k]!! + 1

or similar, to update the map. Kotlin doesn't seem to allow things like

myMap[k]!! += 1

either. Wouldn't it be useful to have a

modify

or

update

function? Is there one already that I missed? It clarifies intent and avoids the repetition of the key:

fun MutableMap<K, V>.update(k: K, transform: (V) -> V) { this[k] = transform(getValue(k)) }
fun MutableMap<K, V>.update(k: K, default: V, transform: (V) -> V) { this[k] = transform(getOrDefault(k, default)) }

Usage would mean that instead of

myMap[k] = myMap[k]!! + 1

you'd be able to write

myMap.update(k) { it + 1}

Hi everyone! Kind of a weird question but I’m trying to restrict access to a method for any subclass. I’m trying to make a builder like this:

open class AnimalBuilder {
    val dog: DogBuilder get() = DogBuilder()

    open inner class DogBuilder : AnimalBuilder() {
        val pug: PugBuilder get() = PugBuilder()

        inner class PugBuilder : DogBuilder()
    }
}

val pugBuilder = AnimalBuilder().dog.pug 
val wrongBuilder = AnimalBuilder().dog.dog.dog

But as you can see, I don’t want the

DogBuilder

to be able to access the

dog

variable available in

AnimalBuilder

. Is there any way to do that?

How do I suppress the new compiler warning "Name contains characters which can cause problems on Windows"? It doesn't show in IntelliJ, only in the Gradle build.

I’m getting when using mutableLIstOf<Any>: Type inference failed. The value of the type parameter T should be mentioned in input types (argument types, receiver type or expected type). Try to specify it explicitly. I thought I understood it but trying to provide this type is being quite hard. I don’t understand which syntax I should use. The case is

private var filteredList = mutableListOf<Any>()

if(filteredList.contains(item.resourceType)

data class Item (
    val resourceType: ResourceType? = null
)

Now if I give it the ResourceType straight it works. But I would like to understand why not. PS: The way I’m going around this, for now, I’m surrounding the case with when(type) and giving the type class directly into it ex:

if(filteredList.contains(ResourceType)

If people are interested, I'm making an advent of code kotlin leaderboard: 1080601-f03a9296 .

There was a YT issue where someone suggested to be able to publish pure common kotlin code (one without expect/actual) that can be imported into any target whatsoever. Can I get a link to that issue?