Either

An ad-hoc Either can be created the usual way:

val left: Either<Int, String> = left("wrong")
val right: Either<Int, String> = right(1)

An Either can be converted into a Validation:

val valid: Validation<Int, String> = right(1).validation()
val invalid: Validation<Int, String> = left("your value still sucks").validation()

A Kotlin Iterable of Eithers can be sequenced as follows:

val eitherOfSeq: Either<List<Int>, Seq<String>> = 
    listOf(left("still does"), right(1)).sequence()