@raulraja serious? I have recently just managed to learn how Either, Try, Option and Validated works. Are you planning to deprecate all of them?

You can only jump threads with Async. Defer is delayed on the start and once it does it's sync and blocking. Async is delayed on the start and the result, which is the minimal requirement to support wrapping coroutines and threading.

but in the middle, the traverse wraps the whole flow into an effect F

hello guys first of all thanks so much for all the effort around arrow, I can feel the energy so to say! I am invited to give a presentation in austria / vienna on "functional programmng with arrow" in late january and I am bit lost with all the changes happening right now (deprecation of adts, arrow-fx, arrow-meta, ...). I can embrace that arrow tries something completely new that does not exist in other languages... which is really cool don't get me wrong. I have a hard time learning arrow myself and I noticed that the little knowledge of fp coming from elm/haskell (or having and rough idea about maybe, either, adts, which are now deprecated, folds etc.) and the little knowledge of kotlin don't really help me out in learning the idiomatic arrow way of fp that is being created right now ... Learning arrow feels more like learning a completely new language (which is fine for me!) compared to e.g. the transition from java to kotlin or learning elm after haskell. I say this because I anticipate that the people I am going to present to will also need very basic and example driven introduction to arrow ("how do I do x with arrow?"), because most of them are even new to functional programming. I try to imagine how this could be done, using my challenges right now as valuable information. So having a hard time coming up with a very concrete question I want to broadly ask: What does a idiomatic arrow program look like? Why do I raise such a question? Because I watched the very polished arrow youtube videos (thanks for the effort) but I unfortunately didn't get a feel of how I was supposed to program with them. Since I knew Option, Either, etc. from before I knew how to apply them, but using them didn't really feel like I am using the the possibilities of arrow in the intended way. So not the pieces but seeing them used together was what I was missing there. So my proposal is that if someone could pair up with me to get me started on putting such kind of examples together then I can keep going on my own doing that for other people that need some examples to get them started ... sorry for the long post! hope to hear from any of you

I can’t find Reader and ReaderApi in arrow 0.10.3, where is it? 🤯

Hi guys, I'm still trying to get my head around thinking functionally and I'm stuck with this scenario val toBeRemoved = mapOf("id" to 2) val testList = listOf(Some("id" to 1), None, Some("id" to 3), Some("id" to 1)) //TODO val expectedOutcome = listOf(None, Some("id" to 2), Some("id" to 1)) Can be done with mutability like so val toBeRemovedMutable = toBeRemoved.toMutableMap() val actual = testList.map { item -> val id = item.first var newAmount = item.second for ((key, value) in toBeRemovedMutable) { if (id == key && value > 0) { val remove = if (value > newAmount) newAmount else value toBeRemovedMutable[key] = value - remove newAmount -= remove if (newAmount == 0) { return@map None } } } Some(item.copy(second = newAmount)) } but I can't think of a way to do it more functionally. Any suggestions?

I will be showing @Bruno what we are doing with Arrow Meta and how it impacts the future of Arrow at 12:30 pm GMT+1 (in 45 mins). Anyone interested is welcome to join and ask questions. meet.google.com/fwc-exgg-yrh

sorry to not ask it during the meetting, but how union types could interact with when expression? I asume that a fold() method will be available, but most kotlin devs are familiar with exaustive when expression, could compiler plugin support it?

can anyone provide a quick example of the syntax that replaces the "! effect {...}" syntax ... and is this already in 0.10.4-SNAPSHOT ?

Hello, I was wondering how to convert

IO

to

MonoK

nicely, could anybody help?

The laws I get but not sure how I would implement it in arrow if I have an

Boolean expression AND Boolean expression AND Boolean expression

😅 Do I implement it on boolean expression or is it a different type/class all together?

it is extermely difficult to learn the arrow features and refactor a codebase while figuring out alternatives to doc 404's such as https://arrow-kt.io/docs/arrow/typeclasses/semigroupal/ and for Inject.

I am not hugely familiar with arrow, and it uses a lot of names that I do not recognize. I'm wondering if arrow offers some magic that would help me with a problem I'm having: I've been writing a units of measurement library for awhile now, and my biggest disappointment is that I can't find a way to get the compiler to automatically know that a conversion between quantity types results in a specific quantity type (instead of erased type) e.g.

val distance = 512.m
val time = 70.s

val speed = distance / time

The compiler only recognizes

speed

to be of type

Quantity<*>

instead of

Quantity<Velocity>

, even though in the code this operation is specifically instantiating a quantity of velocity. Is there some kind of magic in Arrow that could ensure this without me having to hard code every compound quantity conversion? I'm almost certain at this point that this is impossible to do.

Has any thought been given to supporting kotlinx serialization? I'm not entirely sure what would be required on the arrow side, maybe just annotating some things with

@Serializable

? Adding support for it from outside arrow is a massive pain because I have to go through this process: https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/custom_serializers.md#about-generic-serializers. (it's actually much easier to copy-paste the arrow classes I want to serialize and annotate them myself, but that's not exactly maintainable)

Hello there. I'm just exploring whole Arrow's documentation and ... I'm so impressed, it charmed me. Do you recommend any video from conference or something about usage or explaining real life pros/cons or use cases for newcomer like me, with rxjava experience? I'd be delighted

Hi all, another new comer here. I'm reading the docs, and going through Higher Kinds and Typeclasses, and trying to use some of the examples. The multiplyBy2 example I followed fine:

val o = Option.functor().multiplyBy2(Option(1))
assertThat(o.fix()).isEqualTo(Option(2))

But I've just come across this in the dependency injection notes

fun <F> Show<Kind<F, Int>>.printAllValues(fa: List<Kind<F, Int>>): Unit {
  fa.forEach { println(fa.show()) }
}

I'm trying to write some code to use this, but I'm having trouble finding the right form to invoke it. How would I call it with (say) a list of Option<Int> values? Thanks!

Hello, I got a funny one today. I had an IO with a list of items inside, and I needed to apply an IO operation to each element in the list. The issue is solved in two ways, but I'm baffled as why the second-to-last and last options are different. I'm evidently missing something and I would LOVE to get it out of my head.

A question about

unsafeRunAsync

. I have a test with 3 IO objects I've created and done an

attempt()

on, then I want them to run concurrently. I've tried using unsafeRunAsync expecting them to run ... asynchronously, but they run sequentially. How do I make the async IOs run concurrently?

@Test
    fun `io module test`() {
        val ioModule = Module(IO.async())
        ioModule.run {
            val ioS1 = repository.byId(u1).fix().attempt()
            val ioS2 = repository.byId(u2).fix().attempt()
            val ioS3 = repository.byId(u3).fix().attempt()
            <http://logger.info|logger.info> { "ioS1..." }
            ioS1.unsafeRunAsync { it.fold(ioError, ioInfo) }
            <http://logger.info|logger.info> { "ioS2..." }
            ioS2.unsafeRunAsync { it.fold(ioError, ioInfo) }
            <http://logger.info|logger.info> { "ioS3..." }
            ioS3.unsafeRunAsync { it.fold(ioError, ioInfo) }
        }
    }

My equivalent for using Observable was to use

subscribeOn(...)

as follows:

repository.byId(u1).fix().observable.subscribeOn(<http://Schedulers.io|Schedulers.io>()).subscribe(idLogger, errorLogger)
            repository.byId(u2).fix().observable.subscribeOn(Schedulers.computation()).subscribe(idLogger, errorLogger)
            repository.byId(u3).fix().observable.subscribeOn(Schedulers.newThread()).subscribe(idLogger, errorLogger)

How can I fix the

io module test

to run the 3 IO jobs at the same time? Thanks!

note that

<http://Dispatchers.IO|Dispatchers.IO>

here is where the ios are started, and each can run on its own scheduler

I am trying to set up

Lens

code generation in my little learning project. The docs seem to be outdated. This is the commit that attempts it: https://github.com/adomokos/kotlin-sandbox/commit/0ac6eca63e7fffc83db113fd87ba3972807a22a2 What am I missing?

Any tips when migrating from Arrow 0.9.0 to 0.10? I just recently upgraded from 0.8.2 to 0.9.0

I am currently working on a stream Result type

Error<E> | Loading | Success<T>

. I tried to implement

applicative

for the type. What I would like to achieve is the that the

error

would have a higher precedence than

Loading

, but the

ap()

implementation with

flatmap{ .map{ ff() } }

I can not obtain the state of the second state unless the first is success. an example that I would like to achive:

Result.applicative().tupled(Loading, Error) 
// current result: Loading

Instead of the loading I am looking for the

Error

to be returned. is there a good way to execute it? 🤔 is that a good idea t all? 😄

https://stackoverflow.com/questions/59072111/functional-programming-short-circuiting In case anyone has some time to help

@simon.vergauwen is speaking today in Prague about Arrow, Fx, Meta etc in Prague. I believe is getting live streamed don’t miss it!

Is there a hack to have reified functions in Interfaces?

Is there any good examples of Arrow typeclasses in use? I'm trying to wrap my head around when I'd use them compared to conventional methods but it seems to require a little more ceremony than I expect (so I expect I might be using them wrong)