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)]

it removes elements with the same hashcode afaik

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.

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

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

https://kotlinlang.slack.com/archives/C0922A726/p1583961559115700 That’s basically the same question 🙂

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

Thanks!