Ranges

A range is a sequence of values defined by its two ends. It works with numbers, characters, and anything comparable that has a "next".

def r = 1..5
println r
println r.size()
println r.contains(3)
println r.from + ' to ' + r.to

println (1..<5)                 // exclusive end
println (1<..5)                 // exclusive start (Groovy 4+)
println (5..1)                  // counting down
println (('a'..'e').join())
println ((1..10).step(3))

1..5
5
true
1 to 5
1..<5
1<..5
5..1
abcde
[1, 4, 7, 10]

• a..b includes both ends; a..<b excludes the end.
• Reversed ranges count down.
• A range of integers is a List, so list methods work on it.

Ranges in practice

def scores = [55, 67, 89, 91, 42, 78]
println scores[1..3]                     // slice a list
println scores.findAll { it in 70..100 } // range as a test

def age = 15
if (age in 13..19) println 'teenager'

println (('A'..'Z')[0..4])
println ((1..5).collect { it * it })
println ((1..100).sum())

[67, 89, 91]
[89, 91, 78]
teenager
[A, B, C, D, E]
[1, 4, 9, 16, 25]
5050

Ranges are lazy: 1..1_000_000 stores only its two ends, not a million numbers.