Ranges

Ruby Ranges

Ranges are concise and expressive. Use two dots .. for inclusive ranges, and three dots ... for exclusive (the end value is excluded).

(1..5).to_a    # => [1, 2, 3, 4, 5]
(1...5).to_a   # => [1, 2, 3, 4]

You can create character ranges too. They work exactly as you'd think:

("a".."e").to_a   # => ["a", "b", "c", "d", "e"]
("A".."F").to_a   # => ["A", "B", "C", "D", "E", "F"]

Check if a value is inside a range with include?:

(1..10).include?(5)    # => true
("a".."z").include?("m")  # => true

Need an infinite range? Pair a start with Float::INFINITY and use lazy so it doesn't try to create a billion elements at once:

(1..Float::INFINITY).lazy.select(&:odd?).take(5).to_a
# => [1, 3, 5, 7, 9]

Ranges work beautifully in case statements for pattern matching on values:

score = 85

grade = case score
        when 90..100 then "A"
        when 80..89  then "B"
        when 70..79  then "C"
        else "F"
        end

They're also used in for loops and enumeration. Simple, readable, very Ruby.