Either Int String is what I want, but I don't know how to do Left 3 or Right "3" in kotlin

does kotlin have value constructor?

f :: Either Int String; f x = x; f (Left 3) will get Left 3, f (Right "S") will get Right "S"

the function f's parameter type can be Int or String wrapped by Either

it's about polymorphic, for example, f(x) if x is String, then make reverse x and return it, if x is Int, then plus one and return it

x's type can be Int or String

and we still can get 3 from (Left 3) by ff (Left x) = x

now how to do that in kotlin?