kotlinarrow-kt

Are there elegant ways to turn a List into a NonEmptyList in kotlin and arrow?

fun main() {
    val list = listOf(1, 2, 3, 4, 5) 

    if (list.isNotEmpty()) {
        Nel(list[0], list.subList(1, list.lastIndex))
    }
}

According to arrow documents, it seems be able to do it through Semigroup or Monad binding. However, there is no code to replace List with NonEmptyList.

Is there a better way to replace List withNonEmptyList without using subList?

Solution

  • There is a companion function fromList that return an Option<NonEmptyList> or if you are sure use fromListUnsafe:

    val list = listOf(1, 2, 3, 4, 5)

val nelistOption = NonEmptyList.fromList(list)

val nelist = NonEmptyList.fromListUnsafe(list)