Either.kt

// Compile with koltinc Either.kt
// Run with kotlin EitherKt

open class Either<A,B>{
    class Left<A, B>(val left: A) : Either<A,B>()
    class Right<A, B>(val right: B) : Either<A,B>()
}

fun safeDiv(x:Int, y:Int) : Either<Unit, Int>{
    if (y == 0) return Either.Left(Unit)

    return Either.Right(x / y)
}

open class Maybe<A> : Either<A,Unit>(){
    class Just<A>(val value: A) : Maybe<A>()
	class Nothing<A>() : Maybe<A>()
}

fun safeDivMaybe(x:Int, y:Int) : Maybe<Int>{
    if (y == 0) return Maybe.Nothing()

    return Maybe.Just(x / y)
}

// Prints with a Haskell-like syntax :D
fun <A,B> show(result: Either<A,B>): Unit = when(result) {
    is Either.Left -> println("Left ${result.left}")
    is Either.Right -> println("Right ${result.right}")
    is Maybe.Just -> println("Just ${result.value}")
    is Maybe.Nothing -> println("Nothing")
    else -> println(result)
}

fun main(){
    show(safeDiv(3,0))
    show(safeDiv(6,1))
    show(safeDivMaybe(3,0))
    show(safeDivMaybe(6,1))
}