Scala: How to create a range of characters (list, sequence)

Scala Range FAQ: How can I easily create a range of characters in Scala, such as a range of alpha or alphanumeric characters?

I learned recently that you can easily create a range of characters (a Range) as shown in the following examples. Here’s how you create a basic 'a' to 'z' range:

scala> 'a' to 'z'
res0: scala.collection.immutable.NumericRange.Inclusive[Char] = 
  NumericRange(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z)

'A' to 'z' creates a range of uppercase and lowercase characters, along with many of those other characters on your keyboard:

scala> 'A' to 'z'
res1: scala.collection.immutable.NumericRange.Inclusive[Char] = 
  NumericRange(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, [, \, ], ^, _, `, a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z)

Sorry, without digging into it, I don’t know why some of those other characters are included in the range, and characters like >, <, and others are not included.

Update: This question is answered in the Comments section below. The extra characters come from the fact that the range method simply uses the ASCII table of characters which go from a to z, then have the other characters shown, followed by A to Z. (Thanks for the good comment.)

Here’s how to create a range of characters while skipping some of the characters:

scala> 'a' to 'z' by 2
res2: scala.collection.immutable.NumericRange[Char] = NumericRange(a, c, e, g, i, k, m, o, q, s, u, w, y)

scala> 'a' to 'z' by 3
res3: scala.collection.immutable.NumericRange[Char] = NumericRange(a, d, g, j, m, p, s, v, y)

scala> 'a' to 'z' by 4
res4: scala.collection.immutable.NumericRange[Char] = NumericRange(a, e, i, m, q, u, y)

Very cool.

If you ever need to create a range or string of characters in Scala, I hope this tip is helpful.



It's the ASCII table. 'A' to 'z' creates a range from 'A' (ASCII #65) to 'z' (ASCII #122). After 'Z' (ASCII #90) you get those few other characters in the ASCII table ([, \, ], ^, _, `, ASCII #91-96) before you get to lowercase 'a' (ASCII #97).

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