How can I use map and receive an index as well in Scala?

Question

Is there any List/Sequence built-in that behaves like map and provides the element\'s index as well?

Answer 1

There are two ways of doing this.

ZipWithIndex: Creates a counter automatically starting with 0.

  // zipWithIndex with a map.
  val days = List("Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat")
  days.zipWithIndex.map {
        case (day, count) => println(s"$count is $day")
  }
  // Or use it simply with a for.
  for ((day, count) <- days.zipWithIndex) {
        println(s"$count is $day")
  }

Output of both code will be:

0 is Sun
1 is Mon
2 is Tue
3 is Wed
4 is Thu
5 is Fri
6 is Sat

Zip: Use zip method with a Stream to create a counter. This gives you a way to control the starting value.

for ((day, count) <- days.zip(Stream from 1)) {
  println(s"$count is $day")
}

Result:

1 is Sun
2 is Mon
3 is Tue
4 is Wed
5 is Thu
6 is Fri
7 is Sat