Union types and Intersection types

Question

What are the various use cases for union types and intersection types? There has been lately a lot of buzz about these type system features, yet somehow I have never felt ne

Answer 1

For instance with union types one could describe json domain model without introducing actual new classes but using only type aliases.

type JObject = Map[String, JValue]
type JArray = List[JValue]
type JValue = String | Number | Bool | Null | JObject | JArray
type Json = JObject | JArray

def stringify(json: JValue): String = json match {
    case String | Number | Bool | Null => json.toString()
    case JObject => "{" + json.map(x y => x + ": " + stringify(y)).mkStr(", ") + "}"
    case JArray => "[" + json.map(stringify).mkStr(", ") + "]"
}