Shameless plug... In case someone missed it :smile...

# arrow

[simon.vergauwen]

Shameless plug... In case someone missed it 😄
https://www.47deg.com/blog/functional-domain-modeling-part-2/

[thanerian]

Really interesting article @simon.vergauwen I miss out on how to use the equivalent mapOrNull Iterable operator with arrow operators, sometimes I wanna just drop errors during a computation, exist some traverseXXX or a combination of method to archive that?

[simon.vergauwen]

Most types are not able to implement mapNotNull like Iterable since it requires an empty container like emptyList for Iterable.

i.e.

val either: Either<MyError, List<Int>> = emptyList<Int>().right()
val res: Either<MyError, Int> = either.mapNotNull { list -> list.firstOrNull() } // <-- Should become MyError inside Left
// Which value for MyError should we return???

[thanerian]

Sorry, yesterday I was out of PC and could not write code correctly, mi idea it's more close to this

val list: List<Either<Error, Int>> = listOf(left(Error),right(1),left(Error),right(3),right(5))
val result = List<User> = ... // I want to transforms list and store into result [1,3,5]

If list was List<Int?> I could use simple result = list.mapNotNull { it } but what could I do with Either or Validated?

[simon.vergauwen]

list.mapNotNull { it.orNull() }