it's seems like build in types (`Int` etc) copy on assignment, but classes create a reference on ass...

# announcements

[TwoClocks]

it's seems like build in types (Int etc) copy on assignment, but classes create a reference on assignment. (see this simple example : https://pl.kotl.in/tTP-Co4SS). If I want to make my own numeric-ish type is there a way to behave the same as Int on assignment?

[mcpiroman]

Yup, value classes are exactly what you ask for.

[TwoClocks]

can't have var type... so no way to do += ?

[TwoClocks]

Or is Int immutable as well?

[mcpiroman]

no, you should be able to do `+=`just fine, you mutate the outer type type, not inner

[mcpiroman]

Yes, `Int`can be viewed as immutable here. Generally speaking primitive types are considered immutable

[mcpiroman]

@JvmInline
value class A(val value: Int) {
    operator fun plus(other: A) = A(value + other.value)
}

var x = A(0)
x += A(1)

compiles fine for me

[TwoClocks]

hmmm... looks resonable. I'll give that a shot.

[TwoClocks]

my env is having trouble finding @JvmInline. It doesn't seem to exist in kotlin.jvm.*

[mcpiroman]

This is required only in 1.5 I believe, see the link above

[TwoClocks]

ahh.. yeah. I can't upgrade to 1.5 because of a bug in the null .? operator...

[TwoClocks]

it's supposed to be fixed in 1.5.30

[TwoClocks]

strange that I'd get the error about needing JvmInline in the 1.4.x compiler, but then not actually have it... oh well.

[mcpiroman]

Maybe try `inline`not `value`then?