range.adoc

Range

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Overview

Range is used to express a sequence. Sequences have a start point, an end point, and a way to produce successive values in the sequence. In Ruby, these sequences are created using the .. and …​ range operators. The two dot form creates an inclusive range, and the three-dot form creates a range that excludes the specified high value. In Ruby, Ranges are not represented internally as lists i.e the sequence 1..100000 is held as a Range object containing references to two Fixnum objects. If you need to, you can convert a range to a list using the to_a method.

(1..10).to_a -> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Try yourself

Ranges implement methods that let you iterate over them and test their contents in a variety of ways.

digits = -1..9
puts digits.include?(5)          # true
puts digits.min                  # -1
puts digits.max                  # 9
puts digits.reject {|i| i < 5 }  # [5, 6, 7, 8, 9]

Range is also widely used as an interval test i.e seeing if some value falls within the interval represented by the Range. We do this using === (the case equality operator).

(1..10) === 5       -> true
(1..10) === 15      -> false
(1..10) === 3.14159 -> true
('a'..'j') === 'c'  -> true
('a'..'j') === 'z'  -> false

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