kotlinlang #arrow-contributors

@simon.vergauwen I think you've suggested Category Theory for Programmers the other day, am I right? Can you suggest something else for reading about FP? I've read the first 100 pages and I don't like it. It is too abstract and doesn't supply examples from which it would be easy to understand the concepts.

Bob Glamm

07/24/2019, 1:23 PM

@addamsson Is that the Milewski book?

pakoito

07/24/2019, 8:19 PM

cc @addamsson!

pakoito

07/25/2019, 2:25 PM

and frequently it was learned through writing out the implementation

addamsson

08/06/2019, 9:43 AM

@pakoito @raulraja @Imran/Malic I'm back from vacation! What do you think about rewriting the internals of the persistent collections PR in the light of recent improvements to

kotlinx.collections.immutable

🎉 2

simon.vergauwen

08/14/2019, 1:41 PM

That’s a bug in Dokka and it’s flaky. I tried to reproduce it but was unsuccessful, I saw it randomly.

Imran/Malic

08/16/2019, 9:45 AM

Hey Guys, I was working on docs for

Apply

, but I am not sure of the practicality of

Apply

Arrow

, most functions etc, we use are build on top of

Applicative

Functor

. I could not find anything theoretically substantial to promote using

Functor

over

Apply

in some general use cases. Data types like

Map

have valid

Apply

instances, but no

Applicative

. Most of the typeclass machinery in Arrow is build on top of either

Functor

Applicative

. My question is: Can we delete Apply, because it may have instances for any DT that has an

Applicative

, but there is nothing we can do with an

Apply

, because the

Functor

has more to offer.

Imran/Malic

08/28/2019, 9:51 AM

@Rachel made this PR: I am not sure if @Igal Tabachnik is working on the PDF generation but both of you can discuss this here. https://github.com/arrow-kt/Category-Theory-for-Programmers.kt/pull/56 I am currently unavailable for that project.

Imran/Malic

09/15/2019, 10:04 PM

Does anyone know a random source code generator for Kotlin?

raulraja

09/24/2019, 6:42 AM

With this we may be able to rethink the retrofit integration to base it off suspend instead of callbacks https://twitter.com/JakeWharton/status/1176300676751798273?s=19

stojan

10/10/2019, 9:21 AM

Questions related to tech debt (probably) - Any reason Arrow is targeting Java7 bytecode? even Android moved to 8 😄 - Any reason Arrow is using

compile

instead of

api/implementation

Imran/Malic

10/14/2019, 7:51 AM

Thank you for your persistence @Miguel A. Ruiz!! :arrow:💪🏽 https://github.com/arrow-kt/arrow/pull/1493

thanh

10/15/2019, 9:22 AM

and here is my implementation in `FunctorFilter`:

. /**
   * Apply a filter to a structure such that the output structure contains all instances of specified class.
   */
  @Suppress("UNCHECKED_CAST")
  fun <A, B> Kind<F, A>.filterIsInstance(klass: Class<B>): Kind<F, B> =
    filterMap { a -> if(klass.isInstance(a)) Some(a as B) else None }

Imran/Malic

10/15/2019, 9:53 AM

A simple Gist is sufficient

👍 1

pakoito

10/17/2019, 11:15 AM

which one of you wants the shirt the most? 😄

Bob Glamm

10/17/2019, 12:30 PM

TBH I am going to have very limited availability over the next 3-4 days, so as far as I'm concerned @kitttn, it's yours if you want it

❤️ 1

aballano

10/17/2019, 1:11 PM

@thanh not for now, there's a PR for having a Biofunctor IO that Paco started and I'm trying to help with

thanh

10/20/2019, 12:31 PM

Got it @raulraja. I actually finished my fake implement of

ObservableZ<E, A>

in my RxArrow when I was on the way home: https://github.com/lenguyenthanh/rxarrow/blob/master/src/main/kotlin/com/lenguyenthanh/rxarrow/ObservableZ.kt

Jannis

10/25/2019, 10:18 PM

Hey, in arrow the traverse method from the Traversable typeclass is usually (for collections) implemented using foldRight, but haskell's docs at http://hackage.haskell.org/package/base-4.12.0.0/docs/Data-Traversable.html state that travers is left to right. Is that a bug or a conscious decision? I am for changing that, because for infinite structures like sequence traverse would never compute anything and spend all its time forcing the sequence, whereas with a left to right manner it would actually compute stuff (and when used with IO can also abort whenever it wants)

Jannis

10/25/2019, 10:25 PM

Also just having a set order for everything and documenting that somewhere would be good so that this does not vary from type to type

👍 1

raulraja

10/28/2019, 8:21 PM

We can add a safe version based on eval but it won't help in polymorphic functions already based of ap

Jannis

11/06/2019, 7:21 PM

Hi, I am finally getting around to finishing the

Schedule

datatype that will enable users to easily express all sorts of retry/repeat strategies and I am at the point of choosing where to add the retry/repeat methods. Since the whole thing involves delay I was thinking Async or above (using

delay

from coroutines), but then I saw the

Timer

interface which offers some sort of sleep method for

Concurrent

and some other implementations for rx2 and reactor. So the question is, where does this go in the typeclass hierarchy?

rcd27

11/12/2019, 3:29 PM

[SOLVED - invalidate caches in IDEA] Pulling actual

master

-> trying to build ->

Build SUCCESSFULL

, however a lot of references are red in IDEA

Jannis

11/25/2019, 7:50 PM

Hmm, might be, I'll play around with it a bit and see what I need to do to get it working 👍

👍 2

raulraja

12/08/2019, 12:34 PM

@Proof(Subtyping)
inline fun <A> A.first(): Union4<A, Any?, Any?, Any?>

simon.vergauwen

12/08/2019, 8:28 PM

https://github.com/arrow-kt/arrow/issues/1796

Shady Selim

12/16/2019, 6:38 AM

Hi @here I will be heading a Kotlin summit in Egypt and am asking if you have Arrow resources or slides to share to introduce Arrow to the developers in MENA

Jannis

12/20/2019, 4:26 PM

https://github.com/arrow-kt/arrow/pull/1868 This is ready for review, it fixes a lot of issues with

traverse

. Apart from

traverse

now being left to right for (all?) functors, this should not affect any existing code.

Imran/Malic

12/20/2019, 4:27 PM

Does anyone get this error too, rebuild Arrow from master:

Build file '/Users/ulti_mate/IdeaProjects/Arrow_with_Access/arrow/modules/benchmarks/arrow-benchmarks-fx/build.gradle' line: 16

A problem occurred evaluating project ':arrow-benchmarks-fx'.
> Failed to apply plugin [id 'me.champeau.gradle.jmh']
   > This version of the JMH Gradle plugin requires Gradle 5.5+. Please upgrade Gradle or use an older version of the plugin.

Title

Imran/Malic

12/20/2019, 4:27 PM

Does anyone get this error too, rebuild Arrow from master:

Build file '/Users/ulti_mate/IdeaProjects/Arrow_with_Access/arrow/modules/benchmarks/arrow-benchmarks-fx/build.gradle' line: 16

A problem occurred evaluating project ':arrow-benchmarks-fx'.
> Failed to apply plugin [id 'me.champeau.gradle.jmh']
   > This version of the JMH Gradle plugin requires Gradle 5.5+. Please upgrade Gradle or use an older version of the plugin.

stojan

12/20/2019, 4:43 PM

I did the PR that updates that: https://github.com/arrow-kt/arrow/pull/1840 CI passed, 3 times

¯\_(ツ)_/¯

caching issues maybe?

but then... this maybe -> https://github.com/arrow-kt/arrow/blob/d5fa8fc1966b3f335e84338a08a99443dfefe227/build.gradle#L213 I have no idea what it does

maybe it can be removed?

Imran/Malic

12/20/2019, 4:47 PM

I changed the version to 6.0.1 and it looks good so far. Thank you for your answer

stojan

12/20/2019, 4:48 PM

I have never used it before, so maybe it's not needed 🤔

Imran/Malic

12/20/2019, 4:48 PM

We might want a PR for that, but @pakoito needs to approve if that issue is just a local issue on my computer or it makes sense to create a PR. If yes I can do the PR.

I can approve that it works when the wrapper version is at 6.0.1 just as in our gradle wrapper properties.

This is something I observed after unsuccessful rebuilding a couple of times in

benchmarks

stojan

12/20/2019, 5:27 PM

never seen that before 🤔

@Imran/Malic are you using Java8?

Imran/Malic

12/22/2019, 4:41 PM

Yes 🙂

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