invoke

open operator override fun invoke(left: T, ind1: Int): T
open operator override fun invoke(    left: T,     ind1: Int,     ind2: Int): T
open operator override fun invoke(    left: T,     ind1: Int,     ind2: Int,     ind3: Int): T
open operator override fun invoke(    left: T,     ind1: Int,     ind2: Int,     ind3: Int,     ind4: Int): T
open operator override fun invoke(left: T, index: IntArray): T