Hi, I'm new to Kotlin. Amazing language but sometimes it confuses me a lot :slightly_smiling_face: M...

# getting-started

[Slawomir Ziolkowski]

Hi, I'm new to Kotlin. Amazing language but sometimes it confuses me a lot 🙂 Maybe someone could help me there:

fun main(args: Array<String>) {
    val firstList = listOf<User>(
            User(name="P-0"), User(name="P-0"), User(name="P-0"),
            User(name="P-2"), User(name="P-2"), User(name="P-2"), User(name="P-2")
    )
    val secondList = listOf<User>(User(name="P-2"))
    print(firstList.minus(secondList))
}

data class User(val name: String)

I expect that only one P-2 element will be not in the result, but the result looks like this:
[User(name=P-0), User(name=P-0), User(name=P-0)]

[Dan Newton]

it removes elements with the same hashcode afaik

[Dan Newton]

if you used a class instead of a data class it should do what you want

[Dan Newton]

only because a data class overrides the hashCode depending on the class’s properties

[Mike]

Take a look at the minus or - function implementation in the stdlib, and you'll see it's effectively a filter.

So basically, filter all elements from the first list that are in the second.

[Kroppeb]

if you used a class instead of a data class it should do what you want

No, not using a data class would remove no items

[Slawomir Ziolkowski]

thanks for fast responses! Is there any alternative to the minus function? I just need a list without one element from the second list.

[molikuner]

https://kotlinlang.slack.com/archives/C0922A726/p1583961559115700

That’s basically the same question 🙂

[Dan Newton]

https://kotlinlang.slack.com/archives/C0B8MA7FA/p1587211041250800?thread_ts=1587208739.249000&cid=C0B8MA7FA yes, I derped 🤦‍♂️

[Slawomir Ziolkowski]

Thanks!