Scala

Mappings from Scala's Either and MergeableEither types to kotlin-result.

• Either.fold
• Either.getOrElse
• Either.map
• Either.toOption
• MergeableEither.merge

---

Either.fold

<V, E, U> Result<V, E>.mapBoth(success: (V) -> U, failure: (E) -> U): U

Applies success if this is Ok or failure if this is an Err.

val result: Result<Int, Exception> = possiblyFailingOperation()

val message: String = result.mapBoth(
    success = { "Operation produced value: ${it.value}" },
    failure = { "Operation failed with ${it.message}" }
)

logger.info(message)

---

Either.getOrElse

<V, E> Result<V, E>.getOr(default: V): V

Returns the value from this Ok or the given argument if this is an Err.

Ok(12).getOr(17) // 12
Err(12).getOr(17)  // 17

---

Either.map

<V, E, U> Result<V, E>.andThen(transform: (V) -> Result<U, E>): Result<U, E>

The given function is applied if this is Ok.

Ok(12).andThen { "flower" } // Result: Ok("flower")
Err(12).andThen { "flower" }  // Result: Err(12)

---

Either.toOption

<V, E> Result<V, E>.get(): V?

Returns the value if it exists or null if this is an Err.

---

MergeableEither.merge

<V : U, E : U, U> Result<V, E>.merge(): U

Allows use of a merge method to extract values from Result instances regardless of whether they are Ok or Err.

val ok = Ok(listOf(1, 2, 3)) as Result<List<Int>, Set<Int>>
val err = Err(setOf(4, 5, 6)) as Result<List<Int>, Set<Int>>
val mergedOk: Collection<Int> = ok.merge() // listOf<Int>(1, 2, 3)
val mergedErr: Collection<Int> = err.merge() // setOf<Int>(4, 5, 6)