kinda unsure when a top-level function / class / object is most appropriate for doing things like ProjectEuler. Ideas? https://github.com/andrewgazelka/ProjectEuler/issues/2

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Hi everyone, i've got a question about collection, is there any function or trick in kotlin that could merge only adjacent items in collection? for example, i have an object containing string and an integer. let's say i have this array of object: Raw:

[
   {"A",1}, 
   {"A",1}, 
   {"A",1}, 
   {"B",1}, 
   {"C",1},
   {"D",1}, 
   {"D",1}, 
   {"A",1},
   {"A",1}, 
   {"D",1}
]

I'm aiming to merge the adjacent items and add the integer value for each adjacent items, the end result should transform as this: Result:

[
   {"A",3}, 
   {"B",1}, 
   {"C",1}, 
   {"D",2}, 
   {"A",2}, 
   {"D",1}
]

I've searched through basic extensions for Collection, closest i can found is using

windowed

with

step

1 and

size

1, but it seems like i have to loop and map the call multiple times until there are no pairs to get the result i wanted. Is there any other way to get around this? I also tried

zipWithNext

but it gets tricky if there are more than 2 adjacent items on the list

Does anyone use any additional kotlin plugins (intellij/zsh etc)?

no package protected makes me so frustrated... no real purpose of having unit tests in same package as what I am testing... to do unit tests practically would need each thing I am testing to be in a seperate module

I’ve got an issue and I have no idea where it could come from. I’ve got a top level public extension function defined in the common part of a multiplatform project like this:

fun HttpRequestBuilder.useAuthentication() { ... }

HttpRequestBuilder

is from Ktor client. I’m trying to use it in another project which has the above one as a dependency:

private suspend fun postUploadFile(successUrl: String): Unit =
        <http://http.post|http.post>(successUrl) {
            useAuthentication()
        }

http

is a Ktor

HttpClient

. IntelliJ IDEA sees the extension, imported it alone without me doing anything, everything works inside IntelliJ. Then I tried to build.

> Task :compileDebugKotlinAndroid FAILED
e: <myFile>.kt: (9, 37): Unresolved reference: useAuthentication

The reference position is in the imports. What could cause that? I’m posting here because I have no idea where to start. It only seem to happen for this top level extension right now. Maybe it’s a Gradle metadata issue? But then why would IntelliJ see it?

Is

Foo<*>

in Kotlin equivalent to

Foo<?>

in Java?

Is there a builtin function to map a single argument to many functions that take that same argument? i.e.

val myArg = 1
val myFuncs = listOf(::addOne, ::addTwo, ::addThree)

myArg.someCoolMapFunctions(myFuncs)

There’s a stack overflow answer for Haskell to define this function yourself, but I don’t know what the equivalent Kotlin code would be https://stackoverflow.com/a/47501940/7682196

How do you generate a

<http://pl.kotl.in|pl.kotl.in>

URL for the Kotlin Playground?

What is the name for each of these ways to reference a function?

::funcName

funcName

funcName()

? The last one I believe is a function invocation, ie

() -> Unit

, but the first two confuse me.

Is there a good Java/Kotlin lib for handling dates? Something similarly usable as Moment.js

Hello, I don't understand why the compiler complains here about the missing branch in

when

. The

require

clause implies

element

cannot be a

JsonNull

:

fun unbox(element: JsonElement): Any {
    require(element !is JsonNull) { "The token contains null values" }
    return when (element) { // error: JsonNull case missing
        is JsonLiteral -> element.body
        is JsonArray -> element.filter { it != JsonNull }.map { unbox(it) }
        is JsonObject -> element.content.filterValues { it != JsonNull }.mapValues { unbox(it.value) }
    }
}

hello everyone private val CURRENT_DATE_PREF_VALUE = "cdate" to "" "to" refers to what?

map?

Is there a way to reference member extension function?

class A
class B {
    fun A.update(i: Int) {}
}

I have a question about type inference in the example below. Given this method:

fun <R : Any> fromAttr(
        prop: KProperty1<T, R>,
        transformer: (AttributeValue) -> R
    ) {
        transformers.put(constructorParams.getValue(prop.name), transformer)
    }

If I don't supply the type argument I am able to pass a

prop

with a different

R

than

transformer

. For instance:

u.fromAttr(Widget::count) { false }

Where

Widget::count

is a

Long

. I have to use the form

u.fromAttr<Long>(Widget::count) { false }

to get a compiler error. I assume this is happening because of type erasure so Kotlin is inferring

R

to be

Any

?

What are people’s preferred Java community Slack groups? I’d like to join one alongside this one.

is there a

fun Map<K, V>.map()

that returns a

Map<K, V>

?

anybody seen "Insufficient maximum stack size" lately? kt 1.3.30, happens during method inlining using

Katana

for DI.

Caused by: java.lang.IndexOutOfBoundsException: Insufficient maximum stack size.
        at org.jetbrains.org.objectweb.asm.tree.analysis.Frame.push(Frame.java:239)
        at org.jetbrains.org.objectweb.asm.tree.analysis.Frame.execute(Frame.java:281)
        at org.jetbrains.kotlin.codegen.inline.MethodInliner$Companion$analyzeMethodNodeBeforeInline$analyzer$1$newFrame$1.execute(MethodInliner.kt:1031)
        at org.jetbrains.org.objectweb.asm.tree.analysis.Analyzer.analyze(Analyzer.java:187)

Has anyone used TestContainers with Kotlin+JUnit? I'm trying to use it for spinning up a redis container that's controlled by the test suite

is there anything like

Channel#send()

but that does not suspend? I know I can use

Channel(UNLIMITED)

, but I want to have an interface like a channel that I know will never suspend when I send. The reason for this is I have a function which intakes a channel and outputs data so the inner workings of the function can be recorded (for the purpose of displaying internal, intermediate states within the function).

I'm considering moving a large project from Go to Kotlin. It's too big to rewrite in one go so I need to take a phased approach. What's a good way to call Kotlin code from Go? I need (i) nothing too fancy (i.e. not a framework) and (ii) high performance (there'll be 1000s of calls per second).

There is a Kotlin version

1.3.31

? Any info about it?

yeah basically its always there you cant get rid of it, but if you have no

.java

files it almost doesnt take time... makes sense

Different question, when i run maven goals and it does use incremental kotlin compilers, once the maven part is done intellij does this all over again, it compiles the whole thing... is there a way to make intellij reuse what maven did, or basically delegate such compilation tasks to maven? to reuse this the work done

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Hey, maybe somebody can help me: I try to create a property with a list of elements, where the element have to inherit from a specific class and has to implement a specific interface. I ended up in sth like this:

private val <T> buffer: List<T> where T : A, T : SomeInterface

Problem: this is not working since

T

is not used in "its receiver type" - can somebody help me with the correct syntax for my purpose?

Hi, does any one knows a good dependency container to use in Kotlin for backend projects? Good means: work without any configuration and extra plumbing code in trivial cases. E.g. val di = Container.scanAllProject(); di.get(SomeService::class) would create and return a singleton of class "SomeService" with autowiring/resolving constructor injected dependencies automatically.

Does using

const val

instead of

val

in a

companion object

triggers any compilation/bytecode optimisation ?