kotlinlang #arrow

Hi, is it only me who would use a function to clear the `memoize`d cache like https://clojure.github.io/core.memoize/#clojure.core.memoize/memo-clear! or should I go some simpler way and e.g. restart the application?

Imran/Malic

03/31/2019, 8:55 AM

Can someone give me a minimal example for Free (PUN intended)?

simon.vergauwen

04/02/2019, 4:56 PM

I.e.

sequence: (List<Option<A>>) -> Option<List<A>>

which yields

Some

if all options were

Some

None

if one of them was empty.

streetsofboston

04/04/2019, 4:36 PM

IO, BIO, ZIO 🙂 Sorry, couldn’t resist

raulraja

04/05/2019, 10:19 AM

The current proposed names looks like the following. Note this is not the actual impl but just the names.

CatchIO<E, A> // base IO that has built in bifunctor and its parametric to E
typealias IO<A> = CatchIO<Throwable, A>
typealias EnvIO<R, E, A> = R.() -> IO<E, A>

We are open to new names or suggestions that are easy for users so feel free to comment on this message in a thread and we can look into different options

🤔 1

pakoito

04/05/2019, 1:55 PM

I'm in favor of keeping just EnvIO and make the other two an alias using

Nothing

for the fields they don't use.

ivanmorgillo

04/05/2019, 5:57 PM

AdrianRaFo

04/11/2019, 11:02 AM

The

@extension

export the extension functions from a type class

interface Functor<F> {
  fun <A, B> Kind<F, A>.map(f: (A) -> B): Kind<F, B>
}

to inheritors

@extension interface IOFunctor : Functor<ForIO> {
  override fun <A, B> Kind<ForIO, A>.map(f: (A) -> B): IO<B> =
    fix().map(f)
}

ivanmorgillo

04/12/2019, 8:25 AM

hi all, can you point me to an example of mixing Option and Either binding, please? I'm struggling with some inference errors 🤔

Imran/Malic

04/12/2019, 7:57 PM

Am I the only one who see’s this in gradle?

pakoito

04/13/2019, 2:52 PM

hkts aren’t part of the proposal anymore

raulraja

04/14/2019, 11:36 AM

Also the improvements of freeing you from inheritance all together if you choose to not use sub typing and encouraging horizontal composition and separation of data and behaviors.

Sergio Crespo Toubes

04/16/2019, 3:41 PM

override fun getElements(): Either<Throwable, List<Element>> {
	return elementsApi.getElements(authToken)
		.async(IO.async())
		.fix()
		.unsafeRunSync()
		.unwrapBody(Either.applicativeError())
		.fix()
}

This is working for me, but is the good way for using arrow with retrofit?

getElements

return CallK object.

than_

04/18/2019, 9:09 AM

hi is there any way to operate on

Kind<F,A>

type for example to map it to

Kind<F,B>

Imran/Malic

04/18/2019, 2:17 PM

0.9.1 is the latest

kluck

04/18/2019, 3:01 PM

@raulraja Sorry, but I don't understand how to use your link ^^. When I follow it, I get the correct documentation, but I can't see where I should go to query the apidocs myself. The top "Search documentation..." field only gives me answers inside the "regular" documentation, not the apidocs…

kluck

04/19/2019, 2:34 PM

Hi, I'm trying to get my head around using IO (I'm "leveling up" from simply using Either 😛 ). I'm a bit stuck with how/when to actually execute my IO. For example, let's say I have a retrofit api with this signature:

fun getStore(): CallK<StoreDto>

. On the repository layer, I'd like to obtain a Store, but as it might come from the network, I guess it should be wrapped in an IO like so:

fun getStore(): IO<Store>

. My problem resides in the fact that I don't find where I should do my mapping from StoreDto to Store. I have something like this for now:

kotlin
        apiCall.async(IO.async())
            .fix()
            .unsafeRunAsync { either ->
                either.fold( // <-- the result of this is what I'd like to get
                    { IO.raiseError<Store>(it) },
                    { retrofitResponse ->
                        retrofitResponse.unwrapBody(Either.applicativeError()).fix().fold(
                            { IO.raiseError(it) },
                            { storeDto -> IO.just(Store(storeDto.name)) }
                        )
                    }
                )
            }

But this actually execute the code at the repository level, and doesn't return my expected type. I'd like to actually execute this at a higher level, say my android activity in my presentation layer. Any tips on what direction I should take? I'm trying to get inspiration from https://github.com/JorgeCastilloPrz/ArrowAndroidSamples , but I don't understand all that is done there at the DataSource level…

Imran/Malic

04/19/2019, 9:09 PM

I released the very first version of Arrow Docset 0.0.1 , which acts as a productivity tool to get you started with arrow and helps those who uses Arrow on a daily bases to integrate it efficiently in their workflow. Check out the repo and I welcome PR’s :arrow: https://github.com/i-walker/Arrow-Docset/releases Happy Easter😬

:arrow: 2

👏 2

Imran/Malic

04/20/2019, 8:28 AM

so we get a String (City) then we make a request to our DB(with host and port) if our database does not have the city name available we call 3th party app which results us the Weather forcast of that given city // I am trying to transfer some scala code to kotlin, because there are so source examples on how to use tagless final, but thats another convo.

pakoito

04/21/2019, 2:26 AM

handle exception throwing

There’s

Try

, and we’re on the way of deprecating it in favor of

Fx

:arrow: 1

😱 2

Imran/Malic

04/21/2019, 8:22 PM

I am hyped to announce the 0.1.0 version of Arrow-Docset. Giving you a powerful search-engine. Try it out for yourself! https://github.com/i-walker/Arrow-Docset Now it supports: ( supported before - arrow-playground - Guides on the arrow page ) - Type classes - classes - Functions - Types - Packages

👏 14

starke

04/23/2019, 3:06 PM

is there a simple way to do something like add two

Option<Int>

values?

simon.vergauwen

04/26/2019, 8:07 AM

val c = a.flatMap { aRight ->
  b.map { bRight ->
    bRight + aRight.toString()
  }
}

👍 1

pakoito

04/26/2019, 3:28 PM

https://github.com/arrow-kt/arrow/blob/master/modules/core/arrow-extras-extensions/src/main/kotlin/arrow/data/extensions/kleisli.kt#L136

dewildte

04/27/2019, 3:37 AM

Has anyone have an example of dependencies for arrow version

0.9.1-SNAPSHOT

in a

build.gradle.kts

file?

Bob Glamm

04/29/2019, 12:34 PM

IntelliJ seems to fail not infrequently on Arrow code

Trevor

04/29/2019, 11:52 PM

Do folks use the Kotlin REPL when developing? I'm trying to see if I can get it to kinda mirror what I would expect to do in Clojure and stuff, but IDEA doesn't appear to have any commands that let me send code to the REPL and such. Resources on the topic appear sparse, any insights I might be missing?

pakoito

04/30/2019, 9:48 AM

yeah that works too, and it may actually work better because I don’t remember if we skipped the continueOn and other operators until an error handler was found