Small demo of combining custom operators and function literals with receivers.

Caesar.kt

class CaesarConverter {
    // cannot use operator plus because it would be shadowed and not used
    operator fun String.minus(offset: Int) =
        this.toCharArray().map { it - offset }.joinToString(separator = "") { it.toString() }
}

fun caesar(block: CaesarConverter.() -> String) = CaesarConverter().block()

fun main() {
    val encrypted = caesar { "test" - 4 }
    val decrypted = caesar { encrypted - -4 }
    println("test -> $encrypted -> $decrypted")
    // test -> paop -> test
}