How to use a Range in Scala (Range class examples)

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 11.31, “How to Use a Range in Scala”

Problem

You want to see different ways to use a Range in a Scala application.

Solution

Ranges are often used to populate data structures, and to iterate over for loops. Ranges provide a lot of power with just a few methods, as shown in these examples:

scala> 1 to 10
res0: scala.collection.immutable.Range.Inclusive = Range(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

scala> 1 until 10
res1: scala.collection.immutable.Range = Range(1, 2, 3, 4, 5, 6, 7, 8, 9)

scala> 1 to 10 by 2
res2: scala.collection.immutable.Range = Range(1, 3, 5, 7, 9)

scala> 'a' to 'c'
res3: collection.immutable.NumericRange.Inclusive[Char] = NumericRange(a, b, c)

You can use ranges to create and populate sequences:

scala> val x = (1 to 10).toList
x: List[Int] = List(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

scala> val x = (1 to 10).toArray
x: Array[Int] = Array(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

scala> val x = (1 to 10).toSet
x: scala.collection.immutable.Set[Int] = Set(5, 10, 1, 6, 9, 2, 7, 3, 8, 4)

Some sequences have a range method in their objects to perform the same function:

scala> val x = Array.range(1, 10)
x: Array[Int] = Array(1, 2, 3, 4, 5, 6, 7, 8, 9)

scala> val x = Vector.range(1, 10)
x: collection.immutable.Vector[Int] = Vector(1, 2, 3, 4, 5, 6, 7, 8, 9)

scala> val x = List.range(1, 10)
x: List[Int] = List(1, 2, 3, 4, 5, 6, 7, 8, 9)

scala> val x = List.range(0, 10, 2)
x: List[Int] = List(0, 2, 4, 6, 8)

scala> val x = collection.mutable.ArrayBuffer.range('a', 'd')
x: scala.collection.mutable.ArrayBuffer[Char] = ArrayBuffer(a, b, c)

Ranges are also commonly used in for loops:

scala> for (i <- 1 to 3) println(i)
1
2
3

Discussion

In addition to the approaches shown, a Range can be combined with the map method to populate a collection:

scala> val x = (1 to 5).map { e => (e + 1.1) * 2 }
x: scala.collection.immutable.IndexedSeq[Double] = Vector(4.2, 6.2, 8.2, 10.2, 12.2)

While discussing ways to populate collections, the tabulate method is another nice approach:

scala> val x = List.tabulate(5)(_ + 1)
x: List[Int] = List(1, 2, 3, 4, 5)

scala> val x = List.tabulate(5)(_ + 2)
x: List[Int] = List(2, 3, 4, 5, 6)

scala> val x = Vector.tabulate(5)(_ * 2)
x: scala.collection.immutable.Vector[Int] = Vector(0, 2, 4, 6, 8)

See Also

  • The immutable Range class

The Scala Cookbook

This tutorial is sponsored by the Scala Cookbook, which I wrote for O’Reilly:

You can find the Scala Cookbook at these locations:

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