Thank so much for the kind words and wanting to contribute 😻

If it sounds good as a starting point I can take a stab at Eval for https://github.com/arrow-kt/arrow-core/issues/115

also im a bit confused about deprecating

Option

(mentioned in another ticket). it seems like having a

Maybe

type is a standard in most functional languages and is good to have from a user standpoint, even if it duplicates a lot of behavior of Kotlin’s null safety or is equivalent to an

Either

, though I assume I’m missing something about the long term vision for it

and just to pile on some more, I’m getting my fork setup but when attempting to

./gradlew build

I’m getting these errors

Execution failed for task ':arrow-core-data:kaptGenerateStubsTestKotlin'.
> Could not resolve all files for configuration ':arrow-core-data:testCompileClasspath'.
   > Could not find io.arrow-kt:arrow-mtl-data:0.11.0-SNAPSHOT.
     Searched in the following locations:
       - <https://jcenter.bintray.com/io/arrow-kt/arrow-mtl-data/0.11.0-SNAPSHOT/maven-metadata.xml>
       - <https://jcenter.bintray.com/io/arrow-kt/arrow-mtl-data/0.11.0-SNAPSHOT/arrow-mtl-data-0.11.0-SNAPSHOT.pom>
       - <https://kotlin.bintray.com/kotlinx/io/arrow-kt/arrow-mtl-data/0.11.0-SNAPSHOT/maven-metadata.xml>
       - <https://kotlin.bintray.com/kotlinx/io/arrow-kt/arrow-mtl-data/0.11.0-SNAPSHOT/arrow-mtl-data-0.11.0-SNAPSHOT.pom>
       - file:/Users/tavish/.m2/repository/io/arrow-kt/arrow-mtl-data/0.11.0-SNAPSHOT/maven-metadata.xml
       - file:/Users/tavish/.m2/repository/io/arrow-kt/arrow-mtl-data/0.11.0-SNAPSHOT/arrow-mtl-data-0.11.0-SNAPSHOT.pom
     Required by:
         project :arrow-core-data

any advice on addressing this would be appreciated! Thank you!

Yes, while the removal/deprecation of

Option

might seem a bit controversial but we believe it will push FP in Kotlin in the right direction. Beside that you still have

typealias Option<A> = Either<Unit, A>

that offers the exact same semantics, and API if you need it.

?

is superior over

Option

in performance, and we want to supplement the APIs so the removal of

Option

shouldn't be felt from a user point of view. The only technical issue with

?

is that in generic code

A

not constraint as

A : Any

,

A

can be

Int?

and thus using

A?

in generic code can be unsafe as you might be checking the users null instead of your own. So in generic code you should still use

Either<Unit, A>

or

Union2<Unit, A>

(when it becomes available), if you rely on

null

as a signal.

That will encourage more idiomatic Kotlin, with a small gotcha which is inherit to the Kotlin type system.

Please, could you check if there are local changes in your workspace? Did you make any change after cloning

arrow-core

repository?