in an if check,

in

is the same as

contains

. What is the operator function for

in

when we use it in a loop?

It's a regular function called

iterator

.

ok I thought operators always need an operator fun

It's

operator fun iterator()

and the return type needs to conform to

operator fun hasNext(): Boolean
operator fun next(): T

Where T can be anything, including primitives and inline classes, which won't be subject to auto boxing. That would happen if you use the

Iterator

type though because of generics.

thanks

Yeah

just to make that clear, the same operator is used for 2 completely different things

Yes.

ok cool

Are they marked as

expect

?

no

Can you give some examples so we can give a specific answer?

yea if you go into Array.kt or Primitives.kt where Int, Long etc. are declared

They're intrinsic

what does that mean exactly

It's handled in the compiler