Hello what architecture do you suggest for using KMM for android and ios ?

I wonder if the the Kotlin stdlib comes with an alphanumeric comparator for "natural order" of file names like https://github.com/sawano/alphanumeric-comparator

Hi, I was trying to experiment a way to intersect two series in Kotlin efficiently. I have my Range class (similar to Kotlin in a way) defined as

data class Range(
    val start: Int,
    var steps: Int,
    var repeat: Int
)

In practice a Range(2, 2, 5) represents the following sequence:

2, 4, 6, 8, 10

Now I want to write a function

intersect(other: Sequence): Sequence

that given 2 sequences is able to intersect them. Now I’m aware that I can go into the Kotlin ranges and/or build an array and do intersect on them. However what I was trying to do is to find a more efficient (constant) solution just using math. So I came up with this implementation

data class Range(
    val start: Int,
    var steps: Int,
    var repeat: Int
) {

    fun intersect(other: Range): Range {
        val delta = leastCommonMultiple(steps, other.steps)
        val maxStart = max(start, other.start)
        val minStart = min(start, other.start)
        val start = minStart + (delta * ((maxStart - minStart + delta - 1)/delta)) //this is wrong
        val repeat = stepsTo(maxStart, delta, min(getLast(), other.getLast()))

        return Range(
            start,
            delta,
            repeat
        )
    }

    private fun stepsTo(start: Int, delta: Int, target: Int): Int {
        return  (target - start + delta - 1)/delta
    }

    private fun greatestCommonDivisor(a: Int, b: Int): Int {
        return if (a == 0) b else greatestCommonDivisor(b % a, a)
    }

    private fun leastCommonMultiple(a: Int, b: Int): Int {
        return a / greatestCommonDivisor(a, b) * b
    }

    private fun getLast() =
        start + steps * (repeat - 1)
}

But still the way start is calculated is wrong since it doesn’t place the number in the sequence.. I wonder if anyone has solved this problem already and in case you have any suggestion?

How do I specify a default value for a function type parameter? e.g. I want to make the

action

parameter optional by giving it a default "no-op" value

fun move(predicate: (Node<T> -> Boolean), action: (Node<T> -> Unit)) {
   // body
}

Hi

I want to make rhythm game with kotlin. Can you recommend kotlin game development engine?

Hi, is there a way to use Windows Bluetooth api in Kotlin JVM?

Generics question, I’ve defined an interface for my factories and I’m trying to create a mapping so I can pass in the class of an Event & get back the factory which can create it.

interface SchemaFactory<in E: Event, out S: Schema> {

  fun create(event: E) : S
}

class TestEventFactory : SchemaFactory<TestEvent, TestEventSchema>

private val factories: Map<Class<out Event>, SchemaFactory<Event, Schema>> = mapOf(TestEvent::class.java to TestEventFactory())

However I get the following error message on `factories`:

Type mismatch.
Required:
Map<Class<out Event>, SchemaFactory<Event, Schema>>
Found:
Map<Class<out Event>, TestEventFactory>

My Code

fun changeIntToDouble(number: Int) {
    return number.toDouble()
}

but my ide said Type mismatch: inferred type is Int but Unit was expected How can I fix it?

how to wait in kotlin? ex)

fun kotlinlol {
    println("1")
    // sleep 1 sec
    println("2")
}

Hi, I have a question, why is the Kotlin SDK defining extensions methods of classes that haven't any parent or not implementing anything ? Is that better than defining the method inside the class ? What are the benefits so ?

how to make keyboard listener in kotlin? not android

I'm having trouble with the kotlin syntax for methods that appear to have a vararg as the first parameter. I'm trying to call

line.split(": ", 2)

(line is a String). I've tried

line.split(": ", false, 2)

and

line.split(delimiters = ": ", limit = 2)

Hi, is it possible to have a default value for a generic type of a class ? Like that code in TypeScript :

class Test<T = string> {
    readonly thing: T
}

const a = new Test() // this works
const b = new Test<number>() // this too

This message was deleted.

Hi

enum class Role(val letter: Char) {
    APPROVER('U'),
    ADMIN('D'),
    INQUIRER('R'),
    OPERATOR('O');
}

we have create this enum for code readability and we don't have direct control over how server is returning constants for the user roles, so they have done it this way 'U' , R etc apiRespose.role = "U" Role.valueOf(apiResponse.role) will not work ,as it is expecting  'APPROVER' as input . How can i achieve same benefit of Role.valueOf( ) wrt ot the 'letter' attribute in the enum

Hi i have a data class in domain layer and data layer, both has same attribute names, is there way in kotlin to initialized the domain model with the data model, if they have same attribute names ? domain layer model data class JourenyId ( val jr001, val jr002 ... ) data layer data class ApIResponseJourenyId ( val jr001, val jr002 ... )

Hi! 🙂 I am seeing a lot of developers ignoring structured concurrency by launching a new coroutine in a different scope, although they are already in a suspending function or have access to

CoroutineScope

. Real life example which I came across so many times can be a convenience method like this:

fun launchWithLoading(action: suspend () -> Unit) {
    scope.launch {
        try {
            loading = true
            action()
        } finally {
            loading = false
        }
    }
}

Nothing prevents the developer from calling it in a suspending context like:

suspend fun alreadySuspending() {
    launchWithLoading {
        // do stuff
    }
}

or like

fun first() {
    launchWithLoading {
        another()
    }
}

fun another() {
    launchWithLoading {
        // calculate something
    }
}

although rarely they intend to break the structured concurrency. I wonder if there is something like Android Lint but that is purely for Kotlin? Almost everything I've found on the internet points me in the direction of Android Lint. But since this unrelated to Android, I would like to solve it without coupling the solution to Android or Android Studio, so that it can be potentially used in IntelliJ IDEA as well.

Considering this class:

open class KotlinPractice(val id: Int) {
    override fun equals(other: Any?) =
        this === other ||
                other != null &&
                other::class == KotlinPractice::class &&
                (other as KotlinPractice).id == id

    override fun hashCode() = id
}

Is there a reason

other

is not smart-cast and instead I have to cast it to KotlinPractice manually?

Hi. I was trying to see if I could get some information from a

KFunction

without

kotlin-reflect

(using

kotlinx-metadata-jvm

), but I couldn't get

Metadata

with valid information, so I have a question. What I want to achieve is as follows. 1. get the information of arguments and return values from

KFunction

. 2. get

javaConstructor

or

javaMethod

from

KFunction

.

Hi folks! I don't know if this is the best channel to ask you this, be here we go: I have an application built with Spring Boot and Gradle, which connects with Kafka and PostgreSQL. I'm using

resources/application.yml

as the config file. I want to create a specific package for each of this kinds of tests: unit, integration and end-to-end, but now I have a package only for unit tests. The problem is: every time I run the unit tests, my Spring Boot application try to connect with Kafka and Postgres (but for this purpose, I don't need them). How can I avoid to connect with these tools when running my unit tests? Also, do you know some blog post or documentation that shows how to create distinct packages for each kind of tests? Thanks in advance 🙂

Hi everyone, Is there anything available for Kotlin(or Java) similar to https://github.com/SBoudrias/Inquirer.js? I found https://github.com/kotlin-inquirer/kotlin-inquirer but when I run it on windows CLI(which is my project's primary target), the CMD goes brrrrrrr.... 😅 The inputs keep appearing again and again and doesn't wait for the user to give input

I had a thread going in #general that I can no not reply to, what should I do?

I have many `enum`s with the following prototype:

enum class SomeHeaders(val label: String)

(for headers of different tables). How can I write a type parameter (like

val a: ???WHAT???

) so that it will be clear that it's

enum

(so I can use

values()

, etc.) and it had the

label

parameter. The parameter has easty solution: interface, but what about the

enum

limitation?

if a currently experimental annotation becomes no longer required in the future - will there be a compiler warning telling us that we no longer need to opt in? Looking at

kotlin.contracts.ExperimentalContracts

specifically

Hi , is there any way to get all

sealed interface

implementations ? ( Maybe classes or objects )

Something is wrong with my code that works with File IO.

fun main() {
    val strs = listOf(
        "line1",
        "line2"
    )
    val writer = File("src/main/resources/logging/temp.txt")
        .writer()

    strs.forEach { writer.appendLine(it) }
    writer.close()
}

The

temp.txt

file is empty when I run this program. After that the contents of the

temp.txt

file looks something like this,

line1
line2

This is a perfectly reasonable output. However, things go wrong when I run a slightly modified version of the code for the second time.

fun main() {
    val strs = listOf(
        "line3",
        "line4"
    )
    val writer = File("src/main/resources/logging/temp.txt")
        .writer()

    strs.forEach { writer.appendLine(it) }
    writer.close()
}

This is the new version. But this time the

temp.txt

file wasn't empty. It had the output of the first program saved into it. However, after running the new version the

temp.txt

file looks like this,

line3
line4

The contents written by the first program are completely wiped out. Isn't the

temp.txt

file supposed to look like this?

line1
line2
line3
line4

If not then what's even the point of using

append

over

write

? Isn't

append

expected to write new content after the previously added content instead of wiping out and starting afresh? Or, am I missing something?

if Kotlin's

fixedRateTimer

function appropriate and accurate enough to create a countdown timer? And is there any problem with launching a coroutine inside the timer action block?

fun startTimer() {
        timer?.cancel()
        applicationScope.launch {
            val selectedTask = selectedTask.first()
            if (selectedTask != null) {
                taskDao.updateLastActiveTimestamp(selectedTask.id, System.currentTimeMillis())
                startTimerService()
                timerRunningFlow.value = true
                timer = fixedRateTimer(period = TICK_DELAY) {
                    applicationScope.launch {
                        taskDao.increaseMillisCompletedToday(selectedTask.id, TICK_DELAY)
                    }
                }
            }
        }
    }

Can't import

kotlin.io.path

. Tried invalidating caches and restart. Still no luck. Any idea on how to make this work?