Either

sealed class Either<out L, out R>

isLeft	`abstract fun isLeft(): Boolean`
isRight	`abstract fun isRight(): Boolean`

apply	`infix fun <L, R, O> Either<L, (R) -> O>.apply(f: Either<L, R>): Either<L, O>`
flatMap	`infix fun <L, R, O> Either<L, R>.flatMap(f: (R) -> Either<L, O>): Either<L, O>`
fold	`fun <L, R, O> Either<L, R>.fold(lf: (L) -> O, rf: (R) -> O): O`
map	`infix fun <L, R, O> Either<L, R>.map(f: (R) -> O): Either<L, O>`
mapLeft	`infix fun <L, R, O> Either<L, O>.mapLeft(f: (L) -> R): Either<R, O>`

Left	`data class Left<out L> : Either<L, Nothing>`
Right	`data class Right<out T> : Either<Nothing, T>`