receiver.kt

// Notice the parameter is now of type "Workbook.() -> Unit" rather than "(Workbook) -> Unit"
fun workbook(block: Workbook.() -> Unit): Workbook {
    var wb = HSSFWorkbook()
    block(wb)
    return wb
}

fun tryItOut() {
  
    // Since we defined the lambda as using a Receiver Type of "Workbook.()" we can now directly call the methods without referencing the paramter
    workbook {
        setHidden(true)
        setSelectedTab(2)
    }
}