whooooaaaa I have never seen this before. Is this recent? Does this mean Kotlin might be getting u...

# announcements

[Hullaballoonatic]

whooooaaaa

I have never seen this before. Is this recent?

Does this mean Kotlin might be getting union types in the future? That and default type parameters are some of my most desired features for the language. It would help so much with writing generic functions for differing number types, collections types, and more.

The syntax of the hint is not valid syntax however

[diesieben07]

Kotlin has had union types for a long time (if not from the start). They are just not denotable (i.e. you can't write them down).

[Hullaballoonatic]

So could I write a single method that will accept only Int and Double and have access to arithmetic operators? I'm almost certain the answer is no way. But I'd be thrilled if there were

[Hullaballoonatic]

it gets tedious to write stuff like

operator fun plus(o: Int) = ...
operator fun plus(o: Double) = ...

[Hullaballoonatic]

fun DoubleArray.toVector() = ...
fun IntArray.toVector() = ...
fun Array<Double>.toVector() = ...
fun Array<Int>.toVector() = ...
fun List<Double>.toVector() = ...
fun List<Int>.toVector() = ...

and so on...

[Kroppeb]

This isn't a union type, it's a intersection of types.

[streetsofboston]

Arrow is actively working on a compiler-plugin and it will have the ability to allow union types.
https://github.com/arrow-kt/arrow-meta/pull/64

[Matteo Mirk]

The notation you’re seeing in the hint comes maybe from the JVM (just like platform types). As they pointed out it’s not a union type but an intersection, and you can use that for generic bounds: https://kotlinlang.org/docs/reference/generics.html#upper-bounds