I have problems to compile and write own Semigroup...

# arrow

[Imran/Malic]

I have problems to compile and write own Semigroup Instances
also the @instance annotation does not compile

https://www.youtube.com/watch?v=3y9KI7XWXSY▾

[raulraja]

What version of Arrow are you using. @instance(Target::class) became @extension a few versions ago. Latest release is 0.8.2 and we are currently in 0.9.0 snapshot. 0.9.0 is coming out soon.

[Imran/Malic]

I am using 0.8.2. So what would be the current representation of this?

[Imran/Malic]

This seams to work

kotlin
@extension
interface ListKSemigroupInstance<A>:Semigroup<ListK<A>>{
        override fun ListK<A>.combine(b: ListK<A>): ListK<A> =
                (this + b).k()

}

Where do I find more examples how to work with typeclasses ?

[raulraja]

https://arrow-kt.io/docs/patterns/polymorphic_programs/

[raulraja]

Or just search the docs right there for any particular type classes . Most of the important ones are documented or in the process of

[Imran/Malic]

Thank you 🙂

[raulraja]

Any time !