<@UBD6YCVAR> if KEEP-87 is introduced in Kotlin yo...

# arrow

[raulraja]

@Leandro Borges Ferreira if KEEP-87 is introduced in Kotlin you can then have global package level functions that would look like this:

fun <F, A, B> Kind<F, A>.map(f: (A) -> B, with F: Functor<F>): Kind<F, B> =
  map(f)

value.map { it + 1 }

In regard to Set. Set should not map and get back a Set because it can’t form a lawful Functor instance since it can’t guarantee order. More info here https://gist.github.com/tpolecat/7401433#file-gistfile1-scala

What we can do though is work on the SortedSetK instances that are currently missing and that are similar to the ones we have for SortedMapK where you can have a functor instance and provide a proper map.