Scala variable with several types

Question

There are scala's Eitherthat allow a variable to have a value of type 2.

val x: Either[String, Int] = Left("apple")

However, I want to have more than two types for the variable x, for example. {String, Int, Double, List[String] }.

e.g. val x:[type can be either String, Int, Double or List[String]]
//So that I can store either String, Int, Double, List[String] value in x.

Is there any way to achieve this?

Answer 1

IMO the most natural way to express this is to create an ADT (algebraic data type):

sealed trait Foo
final case class Bar(s: String) extends Foo
final case class Baz(i: Int) extends Foo
final case class Fizz(d: Double) extends Foo
final case class Buzz(l: List[String]) extends Foo

And now you can map the pattern to Foo:

val f: Foo = ???
f match {
  case Bar(s) => // String
  case Baz(i) => // Int
  case Fizz(d) => // Double
  case Buzz(l) => // List[String]
}

Answer 2

Look at shapeless coproducts

"formless is of type Coproduct, generalization of Scala Or in an arbitrary number of options"

Answer 3

, , : scala - ,

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• http://docs.scala-lang.org/tutorials/tour/variances.html
• Scala?

I am still participating in Scala, but hope this helps! :)