Kotlin：初始化二维数组

Question

I am in a loop, reading 2 columns from a file. I read R, T combinations, 50 times. I want R and T to be in an array so I can look up the Nth pair of R, T later in a function. How do I put the R, T pairs in an array and look up the, say, 25th entry later in a function?

For example:

for (nsection in 1 until NS+1) {
  val list: List<String> = lines[nsection + 1].trim().split("\\s+".toRegex())
  val radius = list[0].toFloat()
  println("Radius = $radius")
  val twist = list[8].toFloat()
  println("twist = $twist")
  }

Would like to pull radius and twist pairs from a table in a function later. NS goes up to 50 so far.

Answer 1

You can use map() on your range iterator to produce a List of what you want.

val radiusTwistPairs: List<Pair<Float, Float>> = (1..NS).map { nsection ->
    val list = lines[nsection + 1].trim().split("\\s+".toRegex())
    val radius = list[0].toFloat()
    println("Radius = $radius")
    val twist = list[8].toFloat()
    println("twist = $twist")
    radius to twist
}

Or use an Array constructor:

val radiusTwistPairs: Array<Pair<Float, Float>> = Array(NS) { i ->
    val list = lines[i + 2].trim().split("\\s+".toRegex())
    val radius = list[0].toFloat()
    println("Radius = $radius")
    val twist = list[8].toFloat()
    println("twist = $twist")
    radius to twist
}