14 Iteration

Use for to visit each element without managing an index yourself.

main() {
  List<String> steps = ["read", "run", "change"]
  for step, index : steps {
    printLine("${index}: ${step}")
  }
  for step : steps {
    printLine(step)
  }
  printLine("done")
}

Expected output:

0: read
1: run
2: change
read
run
change
done

The first binding receives the element; the optional second binding receives its zero-based index. The loop body runs once for each element, in collection order.

Try it: Remove the index binding and print only the steps.

Precise rules: Reference.