do data classes support deep equals (a is equal to b iff the entire object graph that starts at a and b are equal) ?

how to do type constraints in kotlin?

While we are at generics, What is the difference between

fun <T> Foo()

and

fun <T:Any> Foo()

? So far I have just been using IntelliSense suggestions. I wan't to understand more. Any deep explanation?

How do I make this polymorphically serializable?

@Serializable
sealed class Result<out T> {
    @Serializable
    class Success<out T>(val data: T) : Result<T>()

    @Serializable
    class Failure<out T>(val msg: String) : Result<T>()

    companion object {
        private fun <T> resultContext(serializer: KSerializer<T>) = SerializersModule {
            polymorphic<Result<T>> {
                subclass(Success.serializer(serializer))
                subclass(Failure.serializer(serializer))
            }
        }

        fun <T> stringify(serializer: KSerializer<T>, res: Result<T>): String {
            return Json(context = resultContext(serializer)).stringify(
                Result.serializer(serializer),
                res
            )
        }

        fun <T> parse(serializer: KSerializer<T>, json: String): Result<T> {
            return Json(context = resultContext(serializer)).parse(
                Result.serializer(serializer),
                json
            )
        }
    }
}}

So that If I have a class

@Serializable
data class Person(val name:String)

I can call

Result.stringify(Result.Serializer(Person.serializer()),Result.Success(Person("Andy))) // This says class Person is not registered for polymorphic serialization

I have little knowledge in Polymorphic Serialization. Also, I need to be able to serialize a

Result.Success<Person?>(null)

. Currently I don't know how to do so. Help?

can somebody explain me the difference between inheritance and implementation and how they affect the memory of system?

is it possible to reference an object's member as a kproperty1? rn if i reference a object's member i get a KProperty0 but for my use case it'd be nice if I could use a KProperty1 so i can bound the receiver.

Exceptions vs Result types, value-based classes and NoCopy. https://www.reddit.com/r/Kotlin/comments/hjoyxx/nocopy_compiler_plugin_for_kotlin/ https://www.reddit.com/r/androiddev/comments/hj3yq8/nocopy_compiler_plugin_for_kotlin/ Some interesting discussions were conducted here :)

Hello everyone, I just created a library parsing csv files into data class without old java way of bombarding your data class with annotations. https://github.com/blackmo18/kotlin-grass hope it could be of good use to you. cheers

Has anybody dug into any details around what makes Kotlin use a lot of memory when compiling? I've got a project that consists of a mix of generated and handwritten code and I've had to bump the compiler to 6GB memory to see it complete.. and I am curious. The project is only about 48000 lines (with whitespace) and 160-170 classes (+ a few data classes here and there). The largest kotlin class is 2600 lines long (with whitespace). (targeting jvm -- server style application)

Is there a single-page description of all the kotlin jars published here https://mvnrepository.com/artifact/org.jetbrains.kotlin? In particular, answering the question why would someone add a dependency on one of the jars to their project.

hello stupid question of the day about this code snippet:

while (shorteneds.putIfAbsent(url, this) != null) {}

of course, intellij complains that the block is empty any idea how to write a better version without the complaint? i’m probably missing something from stdlib...

Hi, Can someone guide me to learn Kotlin. I am currently doing 'Kotlin bootcamp for beginners' by google. Where should I head next to learn more?

Anyone knows any good books on learning Kotlin? I was asked by a colleague today and didn't have an answer since I generally don't use books to learn languages.

[generics] hello 👋 Is there a nice way to avoid the extra cast below?

fun <T : AbstractStub<*>> getClient(stubFactory: (Channel) -> T): T {
    val client = stubFactory.invoke(configuredChannel)
    return if (deadlineMs != null) {
        // returns AbstractStub<S>
        client.withDeadlineAfter(deadlineMs, TimeUnit.MILLISECONDS) as T
    } else {
        client
    }
}

was playing around with inlining the

T

but cannot get it to work --- doing the chaining call from from the caller works as expected

val client: HelloGrpc.HelloBlockingStub = getClient { HelloGrpc.newBlockingStub(it) }.withDeadlineAfter(1000, TimeUnit.MILLISECONDS)

How much more milestone release to final?

So, the

LinkedHashMap

is a nice type in that its got the time complexities of a hash map and it preserves insertion order... but its implementation really is pretty gnarly. Does anybody have numbers on how its implementation impacts performance? Is there a more performant (and/or simpler and/or compact) implementation of an insertion-order-preserving-Map if I'm willing to give up some of the more esoteric intricacies of

LinkedHashMap

(eg: degradation to a b-tree if

hashCode == 0

, dynamic-checking for

Comparable

implementations, etc)? Immutability (even via copy-on-write) is also fine. I have maps that have an upper-bound size of 200, and I'm looking to get to lookups on the order of millions per second.

Regarding the new 1.4 version: When would one use

fun interface CreateTodoUseCase { fun run() }

over

interface CreateTodoUseCase { operator fun invoke() }

? I see the latter being used alot for writing UseCases (myself included. Should I switch to functional interfaces instead?

I want to make localization fully from a server, is it possible to load strings.xml from the server and substitute existing local strings.xml

can i accept

>

,

<=

, etc as an argument to a function?

Does Kotlin 1.4 have a target date for a stable release?

are companion objects overridable using inheritance on data classes?

If I have:

interface Something {
   fun foo(bar: Int): List<Int>
}

class SomethingImpl : Something {
   //...
}

val ref = Something::foo

and I want to invoke it, do I do this:

val instance = SomethingImpl()
ref.invoke(instance, 5)

?

Two things I’ve wanted in Kotlin over the last year of tinkering: 1. function types that retain names and allow default arguments 2. a function on data classes that passes all the components as parameters to another function (like, a ‘destructure to target’)

Intellij now automatically adds ‘val’ when missed creating data classes arguments 😮 Best feature - functions don’t need val in parameters but data classes do

Nevermind! Posted in #multiplatform

is there any way to get current iteration using generateSequence?

Any idea, why this fails? https://pl.kotl.in/EW-w9FlLK it says the general contract of

Comparable

is violated but io cannot spot the violation

Hi all, it may be (or not) a dummy question: how to you calculate a unique hash from a data class, in such a way that you have the guarantee (statistically) that two objects are different as soon as their hash are different? (hash may be calculated and stored on different servers at different time)

Is it possible to call an extension function on class A, defined in class B, from outside of class B? i.e.:

class B {
   fun Int.answer(): Int { return 42 }
}

and somewhere else be able to do something like:

fun main() {
        val myB = B()
        val num: Int = 10
        num.apply {
            myB.answer()
        }
}

My quick test tells me no, but is it imposible/nonsensical or am I just invoking it wrong? I want to be able to implement a function on some type A using some state from an instance of type B.