Ranges

A range represents a sequence of values from a start to an end.

Syntax

1..5     # 1, 2, 3, 4, 5      (two dots: includes the end)
1...5    # 1, 2, 3, 4         (three dots: excludes the end)
"a".."e" # "a" through "e"

Example

p (1..5).to_a
p (1...5).to_a
p ("a".."e").to_a
p (1..10).include?(7)
p (1..10).sum
(1..3).each { |n| puts n * 10 }

Expected output

[1, 2, 3, 4, 5]
[1, 2, 3, 4]
["a", "b", "c", "d", "e"]
true
55
10
20
30

to_a turns a range into an array so you can see every value.

Ranges are also useful for checking whether a value falls between two limits — in a case statement, or with cover? / include?:

age = 42
puts "Working age" if (18..65).cover?(age)

Working age

An endless range leaves off the end: (18..) means "18 or more". rand(1..6) picks a random number in a range — perfect for dice.

Common mistakes

• Forgetting parentheses: 1..5.to_a means 1..(5.to_a) and fails. Write (1..5).to_a.
• Mixing up .. and .... When in doubt, check with to_a in irb.