Arrays.kt

package tutorial

import java.util.*

fun main(args: Array<String>){
  val mixedArray = arrayOf(1, 3.14, "hello")

  // array access elements
  println("Element at 1: ${mixedArray[1]}")
  println("Index of 'hello': ${mixedArray.indexOf("hello")}")

  // copy array
  val arrayCopy = mixedArray.copyOfRange(1, 3)
  println("Copy of last two elements: ${Arrays.toString(arrayCopy)}")

  // construct array
  val squareArray = Array(5, {index -> index * index})
  println("Square of 4: ${squareArray[4]}")

  // ranges
  val range = 1..10
  println("11 is in range: ${11 in range}")
  val skippedRange = range.step(3)
  for(v in skippedRange) println("skipped value: $v")

  val rangeToList = range.toList()

  // Loop over array indices / values
  val array = arrayOf(0, 3, 6, 9)
  for(i in array.indices){
    println("$i x 3 = ${array[i]}")
  }
  for((i, v) in array.withIndex()){
    println("($i, $v)")
  }

  // Collection operators
  val numList = 1..5

  println("Sum of list: ${numList.reduce{a, b -> a + b}}")
  println("Sum of list + 10: ${numList.fold(10){a, b -> a + b}}")
  println("List has any Even: ${numList.any{it % 2 == 0}}")
  println("List has only Even: ${numList.all{it % 2 == 0}}")

  val smallerThan4 = numList.filter { it < 4 }
  smallerThan4.forEach {num -> println("Values < 4: $num")}

  val newList = numList.map {num -> num * 2}  // 1..5 -> 2..10
  newList.forEach {num -> println("New value: $num")}

  // Mutable List
  val mutableList = mutableListOf(1, 2, 3, 4)
  mutableList.add(5)
  println("Mutable list: $mutableList, " +
          "first item: ${mutableList.first()}, " +
          "subList: ${mutableList.subList(0, 2)}")

  // (key, value) map
  val mutableMap = mutableMapOf(Pair(1, "hello"), Pair(2, "bye"))
  println("Map: $mutableMap, Map[1]: ${mutableMap[1]}, Map[3]: ${mutableMap[3] ?: "null"}")
  for ((i, v) in mutableMap){
    println("Iterate map: ($i, $v)")
  }
}