kotlin [多层嵌套循环] 转换成一行

RangeLoop.kts

fun <T : Comparable<T>> loop(vararg range: Iterable<T>, action: (List<T>) -> Unit) {
    if (range.isEmpty()) return
    startLoop(range.size, range, listOf(), action)
}

fun <T : Comparable<T>> startLoop(
        rawSize: Int,
        rs: Array<out Iterable<T>>,
        ps: List<T>,
        action: (List<T>) -> Unit
) {
    if (rs.size == 1) {
        rs[0].forEach {
            action(ps + it)
        }
        return
    }
    val tar = Array(rs.size - 1) {
        rs[it + 1]
    }
    rs[0].forEach {
        startLoop(rawSize, tar, ps + it, action)
    }
}

/**
 * 多层嵌套循环
 */
loop(1..3, 4..6, 7..9) { (a, b, c) ->

    println(listOf(a, b, c))

}

//OutPut:
/*
[1, 4, 7]
[1, 4, 8]
[1, 4, 9]
[1, 5, 7]
[1, 5, 8]
[1, 5, 9]
[1, 6, 7]
[1, 6, 8]
[1, 6, 9]
[2, 4, 7]
[2, 4, 8]
[2, 4, 9]
[2, 5, 7]
[2, 5, 8]
[2, 5, 9]
[2, 6, 7]
[2, 6, 8]
[2, 6, 9]
[3, 4, 7]
[3, 4, 8]
[3, 4, 9]
[3, 5, 7]
[3, 5, 8]
[3, 5, 9]
[3, 6, 7]
[3, 6, 8]
[3, 6, 9]*/