to

infix fun <A, B> A.to(that: B): Pair<A, B> (source)

Creates a tuple of type Pair from this and that.

This can be useful for creating Map literals with less noise, for example:

import kotlin.test.*
import java.util.*

fun main(args: Array<String>) {
//sampleStart
val map = mapOf(1 to "x", 2 to "y", -1 to "zz")
println(map) // {1=x, 2=y, -1=zz}
//sampleEnd
}