compising of functions with different types

DifferentTypesFunctionComposing.kt

fun length(str: String): Int = str.length

fun strPlusX(x: Int): String = "string " + x

fun add6To(x: Int): Int = x + 6

fun xMultipleX(x: Int): Int = x * x

operator fun <P1, R1, R2> ((R1) -> R2).plus(f: (P1) -> R1): (P1) -> R2 {
    return {p1: P1 -> this(f(p1)) }
}

fun main(vars: Array<String>) {

    val composed = ::length + ::strPlusX + ::add6To + ::xMultipleX // = ('string' + ((6 * 6) + 6)).length

    println(composed(6)) // 9

}