MapFunctions.kt

sealed class Result {
    fun flatMap(f: (Int) -> Result): Result = when(this) {
        is Success -> f(value)
        is Failure -> this
    }
    fun map(f: (Int) -> Int): Result = when(this) {
        is Success -> Success(f(value))
        is Failure -> this
    }
}
data class Success(val value: Int) : Result()
data class Failure(val message: String) : Result()