Data Types

Arrays and Lists

Read values from a small typed list.

lists Lists keep several values in order and can be indexed.

Arrays and Lists

bonus
ArraysLists.kt
Replay: real traced execution (multi-file project)
fun main() {
    val bonus = 2
    val scores = listOf(10, 20, 30)
    val first = scores[0]
    val adjusted = scores[1] + bonus
    val size = scores.size

    println("first=$first")
    println("adjusted=$adjusted")
    println("size=$size")
}

fun main() {
    val bonus = 0
    val scores = listOf(10, 20, 30)
    val first = scores[0]
    val adjusted = scores[1] + bonus
    val size = scores.size

    println("first=$first")
    println("adjusted=$adjusted")
    println("size=$size")
}

fun main() {
    val bonus = 5
    val scores = listOf(10, 20, 30)
    val first = scores[0]
    val adjusted = scores[1] + bonus
    val size = scores.size

    println("first=$first")
    println("adjusted=$adjusted")
    println("size=$size")
}

  1. bonus ← 2, scores ← [10, 20, 30], first ← 10, adjusted ← 22, size ← 3

    1fun main() {2    val bonus→ 2 = 2 //@bonus=0, 53    val scores→ [10, 20, 30] = listOf(10, 20, 30)4    val first→ 10 = scores[0]105    val adjusted→ 22 = scores[1]20 + bonus26    val size→ 3 = scores.size378    println("first=$first10")9    println("adjusted=$adjusted22")10    println("size=$size3")11}
    outputfirst=10
adjusted=22
size=3

  1. bonus ← 0, scores ← [10, 20, 30], first ← 10, adjusted ← 20, size ← 3

    1fun main() {2    val bonus→ 0 = 03    val scores→ [10, 20, 30] = listOf(10, 20, 30)4    val first→ 10 = scores[0]105    val adjusted→ 20 = scores[1]20 + bonus06    val size→ 3 = scores.size378    println("first=$first10")9    println("adjusted=$adjusted20")10    println("size=$size3")11}
    outputfirst=10
adjusted=20
size=3

  1. bonus ← 5, scores ← [10, 20, 30], first ← 10, adjusted ← 25, size ← 3

    1fun main() {2    val bonus→ 5 = 53    val scores→ [10, 20, 30] = listOf(10, 20, 30)4    val first→ 10 = scores[0]105    val adjusted→ 25 = scores[1]20 + bonus56    val size→ 3 = scores.size378    println("first=$first10")9    println("adjusted=$adjusted25")10    println("size=$size3")11}
    outputfirst=10
adjusted=25
size=3

Follow the List

  1. bonus starts at 2.
  2. scores is 10, 20, and 30.
  3. first = scores[0] reads 10.
  4. adjusted = scores[1] + bonus adds 20 + 2.
  5. The program prints first=10, adjusted=22, and size=3. | bonus | first | adjusted | size | | --- | --- | --- | --- | | 0 | 10 | 20 | 3 | | 2 | 10 | 22 | 3 | | 5 | 10 | 25 | 3 |

Exercise: ArraysLists.kt

Reproduce adjusted=22, then use the pinned bonuses 0 and 5 to predict each adjusted value.