Hello! Is there any trick to make

parTraverseEither

return

NonEmptyList

when called on

NonEmptyList

receiver?

There is a survey by

JetBrains

, check this out: they have

Arrow

option in it! YEAH! (https://surveys.jetbrains.com/s3/kt-ktor-annual-customer-survey-2021)

Hi, how are

generator-scripts/tuple.generator.kts

run in the arrow build? I'd like to add mapN to nullable tuples

Hey all, I see a branch on

arrow-meta

called

as-var-invariants

It seems to add some commits around

pre

,

post

and

invariant

functions. Is this going to enable a DSL for a sort of Design-by-Contract style programming similar to Ada and D, where you can state pre/post-conditions of a method and invariants of a method or class? If so, very exciting! • https://github.com/arrow-kt/arrow-meta/commit/38f6850bbeab3e2df7fffbd1409d0415c57a0006#diff-0cba0892a09ca12cf39e0816[…]8d75d7633e5d6fce55dd30fbfc15e • https://github.com/arrow-kt/arrow-meta/commit/64efe5e7fed1c98dfd9460c79ec02f0eb6477708#diff-d8893c41325132d95cc89c5a[…]6dd9ea55a0c7fc4413d35bfb1d0eb

Hi everyone! I have a very long form and I’m using

ValidatedNel<E, A>.zip

for validation. Unfortunately,

zip

accepts at most 9 arguments. Do you have any suggestions about using

Validated

with more than 9 arguments in an “nice” way?

validatedArg0.zip(
  validatedArg1,
  validatedArg2,
  validatedArg3,
  validatedArg4,
  validatedArg5,
  validatedArg6,
  validatedArg7,
  validatedArg8,
  validatedArg9,
  ::someFunction
)

Brief, possibly dumb question: I'm fairly new to Kotlin -- but not to programming, or to the fundamentals of FP (ADT's, higher-order functions, whatnot. No clue about monoids, endofunctors and the likes though, bit over my head) Am curious about the comparison between Arrow's

Option<T>

and Kotlin's

Result<T>

(which I know Kotlin devs have said not to use directly, though not entirely sure why) And similarly for things like

.runCatching { }

Has anyone transitioned from using the basic FP primitives available in Kotlin stdlib to using mostly/exclusively Arrow, and could share thoughts/opinions and experiences? Would be grateful 🙏 Thank you!

Super brief question: Is arrow multiplatform ready yet? I heard something about one year ago that this was on the roadmap, haven't checked back since.

qq, i noticed that Nullables have

Nullable.zip

but it doesn’t have the extension function

public inline fun <A, B, Z> A?.zip(b: B?, fn: (A, B) -> Z): Z?

i’m quite sure arrow devs have a good reason behind this..?

as well, on zip’s syntax

eitherA.zip(eitherB, ::fn)

Is an alternate syntax like below also planned to be supported?

Either.zip(eitherA, eitherB, ::fn)

for instance, in reactor you have both

Mono.zip(monoA, monoB, ::fn)

and

mono.zip(other, ::fn)

@simon.vergauwen i find it difficult to adjust with your profile without beard

Hi there! Is #arrow multiplatform yet?

i'm looking at

io.arrow-kt:arrow-core:0.13.2

but I don't see the multiplatform modules

Hello, I have a question about Either type resolution/conventions when it comes to errors, and Sum Types.

Hi, I have a question regarding Optics I was reading https://arrow-kt.io/docs/optics/dsl/ and wanted to try the first examle (Street, Address, Company, Employee data classes) but it doesn't work as in the documentation. When I leave the example as is, I get the error:

error: @optics annotated class com.example.Player needs to declare companion object.

In my build.gradle I added the following dependencies:

implementation("io.arrow-kt:arrow-optics:0.13.2")
    kapt("io.arrow-kt:arrow-meta:0.13.2")

Am I doing something wrong or is this just missing in the example code snippet? In this question https://stackoverflow.com/questions/58243913/arrowkt-optics-annotation-not-generating-code they use arrow 0.10.0 and here it is still required and it looks to me, that back then it was still in the documentaion. So I would guess, that the companion object isn't required anymore in 0.13.2. Or am I wrong?

Hello, I found a cross-browser issue with the documentation. Not sure of the scope affected, looks like potentially a small impact.

Hi! I have a data class that I’m generating optics on like this. But I’m finding that I now need to add a lot more constructor params to it. So I’m hitting the error “Iso generation is supported for data classes with up to 22 constructor parameters.” What’s the quickest way around this? Is there a way to tell arrow to ignore some params?

Hi all. This maybe a lame question, but how "heavy" is Arrow Optics? I mean dependency wise, method count wise etc. We are evaluating adding it to our Android project (because copy-copy-copy... enough is enough!), but a bit afraid of Arrow size. Never used it before. Also, how will it be performance wise considering Android? I suspect everything will be OK.

Hello all, new to the channel. I’m working with the “Functional Programming in Kotlin” book by Manning. Though this book was just finalized in August, they appear to be using some deprecated Arrow library code in their code examples. Here’s an example from Chapter 6: Listing 6.18. State propagation using a for-comprehension

val ns2: State<RNG, List<Int>> =
   State.fx(Id.monad()) { 
       val x: Int = int.bind() 
       val y: Int = int.bind() 
       val xs: List<Int> = ints(x).bind() 
       xs.map { it % y } 
   }

Using latest Arrow libs, the above snippet fails syntax checker in Idea. ‘Id’ is not recognized, and Arrow docs say it was slated for deprecation. Wondering if anyone can help refactor this to current Arrow version, or recommend previous version this will work with? Asked on Manning forum, but got no reply.

Hi team! I have a question around delimited continuations. Context: I’m trying to use arrow continuation to convert the ergonomics of an internal data structure that I have in some internal project. It’s somewhat a kleisli, which shape looks like the following:

data class ExecutionPlan<out A>(val runPlan: suspend (PlanConfig) -> A) {
  fun <B> flatMap(fn: (A) -> ExecutionPlan<B>): ExecutionPlan<B> = ...

  // map, zip, traverse
  // etc...
}

Prior to arrow 0.13 it was leveraging

ExecutionPlan.monad().fx { … }.fix()

Now that is not available anymore and I’ve refactored the code to nested flatMaps.. which proliferated in the codebase, and is causing some pain..

// what we have now:
val plan = planA.flatMap { a ->
  planB.flatMap { b ->
    planC(a, b).flatMap { c ->
      // ...
    }
  }
}

// what we want:
val plan = executionPlan { 
  val a = planA.bind()
  val b = planB.bind()
  val c = planC(a, b).bind()
  c
}

I’m wondering how i might leverage delimited continuation to implement this?

fun interface ExecutionPlanEffect<E, A> : Effect<ExecutionPlan<A>> {
  suspend fun <B> ExecutionPlan<B>.bind(): B = ???
}

thanks!!

Forgive me, I’m coming back to android after some time away. I’ve updated to the latest stable version of Arrow (0.13.2) and I’m trying to use monad comprehensions. I’m running into an issue where

bind

is not defined. I’m currently using core, optics, and meta (via kapt). What am I doing wrong?

Is there a way to call Validated.zip on an Iterable instead of one of the overloaded forms? Is this a JVM optimization (I’ve seen Clojure do similar overloading instead of vararg). eg.

val someIterable : List<Validated<MyError, String>> // from a map or something similar
someIterable.zip(Semigroup.nonEmptyList<MyError>()} {array -> ... }
//or
Validated.zip(someIterable, se) {array -> ... }

I’m borrowing Rx’s api for zips / FuncN for f. Is this a JVM optimization? (I’ve seen Clojure do similar overloading instead of a single vararg form)

Hi, and sorry for the probably dumb question, but where is

Applicative

in the latest release? Or what should I use instead?

Is there an official date release for Arrow 1.0? I would like to write an article about Arrow and time it with the release of 1.0

Hi all, I would like to report/fix some formatting issue in the doc

Hello people: I’m wondering if it would be possible to use Arrow in a Multiplatform project

2nd question: Dos anyone can tell how weight is Arrow in Kb’s?

Do you guys have an explicit list of supported targets for KMM? I’m running in this issue right now :

Could not find io.arrow-kt:arrow-core-iosx64:unspecified