so I have a dilemma cc @raulraja

nobody has implemented applicativeerror

because the interfaces have a diamond inheritance and they’re a PITA

MonadError has literally no functions to implement

plan A: kill APError

plan B: a bunch of these babies

@pakoito uploaded a file: Untitled

It has to be kept separate because otherwise you can't lift errors in non monadic contexts for example in the case of

Validated

which only forms an

Applicative

It's also one of the most used type classes in tagless programs in areas around paralelism. I use it.

What we need to do is implement those instances correctly if it's possible without relying on the monad instance.

Kotlin does not do trait style linearization and has a model more similar to Java which leaves us with having to reimplement methods because it can't pick from which instance to get them from.

okay, so there are only 2 collisions

we should be good

lemme finish the effects ones and let’s re-assess

👍

The other thing to consider is that type classes matter not only to our data types but to the users created ones. If we remove

ApplicativeError

we would be taking it away from users too since they may have data types that can't derive monads and then we leave them without a way to deal with errors even if they could support them.

e: /Users/paco/Coding/Kotlin/arrow_workbench/arrow/arrow-effects-rx2/src/main/kotlin/arrow/effects/FlowableKW.kt: (171, 57): Object is not abstract and does not implement abstract member public abstract fun <A> handleErrorWith(fa: HK<FlowableKWHK, A>, f: (Throwable) -> HK<FlowableKWHK, A>): HK<FlowableKWHK, A> defined in arrow.effects.FlowableKWEffectInstance

AAAAAAAAAAAAHHHHHHHHHH

okay nevermind it was a silly copypaste mistake

welp I forgot to create a branch so it went straight to master

go me

that’s the docs

and the instances

Any1 up for proof reading docs? https://github.com/arrow-kt/arrow/pull/617/files#diff-ff900390536032cb25b42622a0aaf443

Then it can be merged 🙂

one nit, but good overall!

@pakoito the code related to that line is right below it.

Obviously that was not clear any suggestion on how to improve?

Arrow provides some instances like

ListKW

indexed by index position.

make it into

Arrow provides

FilterIndex

instances for some of its datatypes that can be filtered by index, like

ListKW

and

MapKW

. You can look them up by calling

FilterIndex.filterIndex()

.