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kotlinlang

By the way, which is better — Java way with None and Some declared as one class (Optional), or Scala way with sealed class (actually, three classes instead of one)?
I have single-class Either implementation, bit it has extra flag which says whether it is left or right.

I'd go with the sealed class approach with multiple classes in order to have a single responsibility (makes the code cleaner IMHO, because if i want to look at the behaviour of None, i have to skim through if/else and find out which one belongs to None)