Handle the 4 possible cases when dealing with 2 `Option` objects.

Handle4CasesFrom2Options.kt

sealed class QuaternaryCase<T> {
    data class Both<T>(val a: T, val b: T) : QuaternaryCase<T>()
    data class OnlyA<T>(val a: T) : QuaternaryCase<T>()
    data class OnlyB<T>(val b: T) : QuaternaryCase<T>()
    class None<T> : QuaternaryCase<T>()
}

fun <T, R> Option<T>.map2Case(b: Option<T>, f: (case: QuaternaryCase<T>) -> R): R {
    return Ior.fromOptions(this, b)
        .map { ior ->
            when (ior) {
                is Ior.Left -> QuaternaryCase.OnlyA(ior.value)
                is Ior.Right -> QuaternaryCase.OnlyB(ior.value)
                is Ior.Both -> QuaternaryCase.Both(ior.leftValue, ior.rightValue)
            }
        }
        .getOrElse { QuaternaryCase.None() }
        .let(f)
}

fun exampleUsage(a: Option<Int>, b: Option<Int>) {
    val value = a.map2Case(b) {
        when (it) {
            is QuaternaryCase.Both -> it.a + it.b
            is QuaternaryCase.OnlyA -> it.a
            is QuaternaryCase.OnlyB -> it.b
            is QuaternaryCase.None -> -1
        }
    }
}