Add asRightIn, asLeftIn and asSomeIn for anyF

[geirolz]

Hi guys! This PR adds some methods to map an F[A] into F[Either[L, A]], F[Either[A, R]] or F[Option[A]].

Example

val fa: IO[Int] = IO.pure(1)

val faRight: IO[Either[String, Int]] = fa.asRightIn[String]
val faLeft: IO[Either[Int, String]] = fa.asLeftIn[String]
val faOption: IO[Option[Int]] = fa.asSomeIn

And for the naming, here a recap

val a: Int = 1 
val fa: IO[Int] = IO.pure(a)

val right: Either[String, Int] = a.asRight[String]
val faRightFromA: IO[Either[String, Int]] = a.asRightF[IO, String]
val faRightFromFA: IO[Either[String, Int]] = fa.mapAsRight[String]

What do you think ? Is there already something in place that I didn't found ? If not, do you think the name is coherent ?

[benhutchison]

Similar questions about how much use these would see as here

[danicheg]

I was the one who added this In postfix in the naming within FEither / FOption syntaxes, and I don't think it should be reused any-elsewhere. In the context of the mentioned syntaxes, it emphasizes the intention of applying the provided function to the value of the inner context (Either / Option). But seeing that postfix is used that way is a little bit confusing.

[geirolz]

Thinking more on this I agree with you. I still feeling that we need these methods to "map and wrap" an effect F.

What about something like mapAsRight, mapAsLeft and mapAsSome.
At the end they are something like this

IO.pure(1).map(_.asRight[String])// IO[Either[String, Int]]

// with the new operator
IO.pure(1).mapAsRight[String]// IO[Either[String, Int]]

I don't know, I don't have many ideas at the moment

[jwojnowski]

Hi! I was just checking issues/PRs before proposing exactly the same thing, with the originally proposed names: asRightIn/asLeftIn/asSomeIn.

Maybe you'll find my thoughts on the naming helpful. To me, these operations are performed on the value in the context of an F, which is quite similar to mapIn, flatMapIn. Somehow, asRightIn/asLeftIn/asSomeIn felt natural to me and I actually was a bit surprised to find out they’re missing.

So, any plans of settling on the naming and merging the PR? 😉

[benhutchison]

OK. Lets get this merged, it's sat long enough, and a 2nd user wanting same thing is evidence for usefulness.

👍 from me, are you ok to merge in current state @danicheg ?

[danicheg]

@benhutchison it's good to go!